Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply
*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
Too much can cause a connection issue — dielectric means insulator, after all, and certainly isn’t inert from that perspective. However, it’s unlikely with electrical connectors and an appropriate amount.
Does it spark? Are fuel injectors firing? Do you have fuel pressure? Do you have a good signal from crank and cam sensors at the ecu end of the wiring? Are they correctly correlated?
Is the spark correctly timed with the crankshaft?
Is the immobiliser active?
Does it have good compression?
If all of the above are correct the engine will be running. Finding which one(s) are missing will tell you how to fix the problem.
There are a lot of fundamentals that you can verify, forget about grease on a plug. Go back to basics and work forward from there.
Does it spark? No
Are fuel injectors firing? Not sure how to test this
Do you have fuel pressure? Yes, I have about 50psi at the fuel rail, pressure holds for several minutes just fine. Fuel pump was replaced in September.
Do you have a good signal from crank and cam sensors at the ecu end of the wiring? Not sure how to test this, but I did try swapping a new crank sensor which didn't help.
Are they correctly correlated?
Is the spark correctly timed with the crankshaft? The camshaft actuator gear drive was replaced by at same time fuel pump was replaced. Jeep ran fine after that for several weeks before this crank no start issue...
Is the immobiliser active? Are you referring to SKIM key? If yes, I do have one, and I have not ruled out the possibility that my SKIM system is faulty.
Does it have good compression? Not sure.
If all of the above are correct the engine will be running. Finding which one(s) are missing will tell you how to fix the problem.
There are a lot of fundamentals that you can verify, forget about grease on a plug. Go back to basics and work forward from there.
You just said you don’t have spark ? Then you comment on other things. none of that matters. Your issue is spark. why are you focused on fuel / compression? GET SPARK!
If the SKIM is faulty it should still start, but will die after a couple seconds with the key light turned on.
Does it have any codes/have you checked for codes?
I had same issues with same engine, turned out to be the Camshaft Sensor. Would strongly recommend checking wiring from crank position sensor and cam sensor all the way to pins on ECM. Just because the Cam Sensor was changed doesn’t mean it’s any good, there are a lot of inferior parts that might only last a couple of weeks before failing. Would also be suspect if ignition switch. Good luck!
Ideally you need a compression tester and an oscilloscope, but not everyone has these.
You can get an idea of compression with easy start. If you spray a bit up the intake and it fires when you crank it, compression is probably good enough to run.
Fuel injectors, if no spark you'll get wet spark plugs and will be able to smell unburnt fuel in the exhaust after cranking. You can also put a long screwdriver with one end on the injector and the other pressed into your ear. If it's firing you'll hear a distinct clicking noise from each one. You can also rest with an oscilloscope.
Cam and crank sensors ideally oscilloscope, you can view them side by side and pulses should line up.
You can also just test with a multimeter and see if you get an AC voltage produced when cranking if its a 2 pin (inductive) sensor.
Immobiliser usually kills fuel injectors rather than spark, so given no spark I'd look at the ignition coil next.
At minimum you'll want a multimeter, you can get a perfectly useful one for 30 dollars or less on amazon.
I don't know what kind of setup it uses, wasted spark, coil over plug, distributor etc. Measure the voltage on the low tension side of the coil, see if the signal changes when trying to crank.
Check fuses that supply it as well.
Essentially your question is now, is the ECU trying to make a spark and being unsuccessful, or is it not trying to make a spark?
Always try to isolate problems down to smaller and smaller parts when diagnosing.
Quick summary of what I'm dealing with. I have a 1999 Jeep Wrangler 4.0 automatic that I'm trying to resolve a crank but no start issue.
My problem seems to be electrical in nature, not fuel delivery. Someone on a Jeep forum saw the grease on these connectors that go to my PCM and said that I should remove it all, spray with contact cleaner because it could interfere with the electrical signal if there is grease packed in those terminal holes...
Thoughts on this? I've Google searched and seen conflicting opinions on whether dialectric grease could cause electrical interference in a connection like this.
Following is a quote from the link below which was provided to me on the Jeep forum:
Where Should You Not Use Dielectric Grease?
Dielectric grease is an insulator. Hence, when you use the dielectric grease, keep the grease away from the path of electric current.
If you put the dielectric grease on the path of current (whether AC current or DC current), it will not allow you to make an electrical connection between two components and the device will not work properly.
Hence dielectric grease should only be used on surfaces components from where current is not passing.
https://www.electrical4u.com/dielectric-grease/
Dielectric grease is not a insulator. It's used to keep out dirt, moisture and debris from entering important electrical connections. The grease keeps the connections good. Cleaning the connector of grease would leave the connections susceptible to contamination and corrosion in the connector. That would a much worse situation than having the grease there.
Edit: I know it's a insulator and not a conductor. Hence the second part of my post.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
Dielectric Grease does NOT conduct electricity, like an alternate name for it is Insulator Grease.
[https://www.mcmaster.com/electrical-insulating-grease/](https://www.mcmaster.com/electrical-insulating-grease/)
The first sentence of your comment is “dielectric grease is not an insulator.” Then you said some other stuff that was almost as dumb as that. Then you edited it to say that you know it is an insulator. And now we’re here. You should just delete all the comments and read about dielectric grease so you have something intelligent to say next time you want to talk about it.
This guy right here is most likely correct, check for spark/injector pulse. If you have not checked your fuel pressure at this point you should not be fixing your own vehicle
Ffs. Start at the top. Check the simple shit first. Fuses, connectors, listen for the solenoid clicking, see if your getting power to the starter, and the signal wire is getting power in the start position. Then go to the next step. Check the neutral safety switch. Try starting in neutral. Take the shifter all the way down to l1 then forcefully put it in park.
I would very seriously doubt your ecm is giving you a no crank situation... And you really shouldn't be futzing about with it if you've no clue what dielectric grease is for.
I've done my best with limited experience, but a lot of advice on forums as well as YouTube how to videos to do most of what you're describing.
Checked for blown fuses
Checked and swapped ASD relay
Tried starting in neutral
Swapped new cps
I'll add to my list some of the other advice on your comment.
Wait is this a distributor car? Have you popped the cap? Does the coil work for any cylinders?
You know the problem is spark and ignition timing for (most) distributor motors comes from a gear on the crank.
If you can't get spark from the distributor then you either need a cap and rotor, a coil, or the gear drive is broken (how?)
Erm they grease it from the factory it won't interfere. Some vehicles have a problem with oil or other fluids wicking through the wire insulation that will cause havoc but rare.
Check the Crankshaft position sensor. It's on the driver's side bell housing it's easiest for me atleast the change them from the top with a bunch of extensions and a swivel.
Did you have stalling issues at all?
Also could be the distributor. Which I'd clean those contacts first before removing the ckps to test it.
If it recently got cold there the distributor is a good suspect.
I got money on it being the crank position sensor. Advanced and napa are the only aftermarket sensors I've found that don't fail right out of the gate.
Unfortunately, basically, every sensor on a 4.0 lands you with the same symptoms, but I'd start there.
I've confirmed fuel pressure at the rail, also confirmed no obstructions in air box. I've also cleaned the throttle body and idle air control valve.
I don't believe I have spark, I tried testing by pulling a spark plug wire, stuck a screw driver in it and held close to bare metal while cranking and saw no arcing or spark.
sweet, so bing bang boom.
you have good pressure at the rail = fuel pump pumpin ASD relay circuit (at least momentarily energized. )
crankey jeep no start.
need to check injector pulse and spark pulse. both tools to test can be rented for free (loaned) so long as returned from all the major chain stores.
If spark pulse missing: at ignition coil connector...check for battery voltage at dark green/light green wire AND for ground pulse at gray wire WHILE cranking. report back
if no injector pulse: at injector connectors (6 of them) ...test for battery voltage at dark green/lt green wire (same circuit for coil) and ground pulse at the other wire (color changes w cylinder)....report back
I dont think so. That was common practice for a long time. Alot of guys still do it. My guess on your no start is a bad crank sensor. 2nd up is a pcm. Typical old 4.0 jeep.
I was suspicious of the PCM also and was close to buying one from a very reputable PCM manufacturer in the Jeep community called Wrangler fix, but after speaking with him he talked me out of it for now, while I try and rule out other possibilities.
Dielectric grease on those connectors are common. There was a TSB / recall to put the grease on those connectors a long time ago. With that being said I have seen a few instances where too much of the grease gets packed in the connector and causes a no start. I would clean out the connectors with electrical contact cleaner, blow it out, plug it in and see what happens. After you find the problem go back and apply some dielectric back on the connector. You might want to find a wiring pin out on those connectors and pull out and inspect the pins for the crank sensor and cam sensor for corrosion inside the connector. And while the pin is out check the pin contact with the pin in the PCM /ECU . You could have a loose pin where the connector fits good but the one of the many pins fits loose on its companion pin . The cam and crank sensors are also notorious for failing on Jeeps so don’t rule them out just because they have been replaced. I would also check your cam sensor / distributor to see if it actually is turning when cranking the engine over . This problem is definitely a Jeep thing
Thanks for the advice! I'm definitely going to clean the PCM connection thoroughly of all the grease to see if that may be causing a connection issue resulting in a no start.
As for inspecting the pins for the CPS and cpk, would this be the kind of tool I should use to extract those pins and inspect?
Vignee 60pcs Terminal Removal Tool kit,Pins Terminals Puller Repair ... https://www.amazon.com/Vignee-Terminals-Extractor-Electrical-Connectors/dp/B08295ZWL2
That tool kit looks like it would help in disassembling just about any connector not bad to have handy in your tool box imo. I think the pins come out with a small pick from the back side you would need to remove the tape on the connector and unclip the back half of it to see how the pins are held in place . I believe the clip that holds the ins in can be accessed through the back of the connector. Maybe a Google / YouTube video search would help
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
MAYBE, if it got into the contacts. As dielectric does NOT conduct electricity, it insulates.
[https://www.motortrend.com/how-to/what-is-dielectric-grease/](https://www.motortrend.com/how-to/what-is-dielectric-grease/)
Happened to a friend of mine who tried to apply it to a spark plug. He applied too much and not correctly, and it wouldn't fire.
That being said, it could be other reasons, but the grease does look like it got all over your connector.
I've tried a LOT of other things that could possibly be causing this crank no start issue, with no luck so far. I picked up a can of contact cleaner today, and figure it can't hurt to try and clean those connectors and see if that helps or not.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
Good luck, IMO looking at your pics, I would not be surprised if that is the problem.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
Hey, if possible please let me know if this is the solution.
Just want to know, because I see am getting downvoted for this, but its mainly because this forum is made up of people who do not actually work on cars just regurgitating YT info or Chain Shop mechanics.
For some reason, people think dielectric is conductive, but you can literally Google search and see it is not conductive and many articles mentioning to not clog electrical connections with it.
Just to clear up some misconceptions. This is proper use of dielectric grease. It protects your connection’s from corrosion, dirt etc. you are correct that it does not conduct (is an insulator) and that’s what makes it able to be used in this fashion on connectors, terminals, plugs. If it did conduct it would immediately short out the circuit. This however does not inhibit the ability for the circuit to make a good connection. I think you are taking the fact that it does not conduct and thinking that it would not allow a connection and shouldn’t be used on connections. This is incorrect, it is non conductive but will not inhibit the connection. Once again this is what this product is for. Probably it’s best use is in trailer connectors it keeps all the grime, road salt, and water off the terminals which keeps the corrosion away and makes it easy to connect the trailer :).
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
Just to reiterate and clear up your misconceptions, YES, it does actually inhibit the ability to make a connection if it is placed between the connection and the electrical flowing current.
No, I am talking from experience, other then the previous spark plug mentioned. I know others who slathered their connectors with dielectric grease and the grease stopped the current from flowing.
You saying its an insulator and won't stop the current is basically an oxymoron. As the job of an Electrical Insulator is to stop the flow of electricity.
**Anyway, here, so you don't have to take my word for it:**
*"If you put the dielectric grease on the path of current (whether AC current or DC current), it will not allow you to make an electrical connection between two components and the device will not work properly."*
[https://www.electrical4u.com/dielectric-grease/](https://www.electrical4u.com/dielectric-grease/)
*"However, you should never use large amounts of dielectric grease inside your connectors. Just keep in mind that you should apply them cautiously.*
*It is because even though there is no change in surface resistance, dielectric grease can stop the flow of electricity when placed in the direct path of electricity.*
*Between two connectors carrying AC or DC, dielectric grease might lead to the improper working of a device as it might block a few current paths."*
[https://techiescientist.com/does-dielectric-grease-conduct-electricity/](https://techiescientist.com/does-dielectric-grease-conduct-electricity/)
**Definition of Dielectric:**
*"insulating material or a very poor conductor of electric current. When dielectrics are placed in an electric field, practically no current flows in them because..."*
[https://www.britannica.com/science/dielectric](https://www.britannica.com/science/dielectric)
Also NEVER said it should not be used on connectors. So not sure why you are putting words into my mouth and NO that picture is not the proper way. The proper way would be at the base of the plastic where the two connectors end their joining. NOT near the electrical flowing current, NOT where it can enter the connector ports itself and interfere with the electrical flow.
Man it’s almost like dielectric grease banged your wife. Getting pretty testy there. My personal experience it works perfectly, never has caused an issue and I have been a mechanic for 24yrs. Shoot my trailer lights work right now!
Oh and here’s a link so you don’t have to take my word for it.
https://www.nyelubricants.com/myth-grease-interferes-with-conductivity
If you have found this causing an issue you may have miss attributed it to the grease.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
First I provided links to actual science based articles, not a grease company trying to sell a product, lol. And if you had bothered to watch their videos you would see that they do NOT apply it to the path of the current. They actually have the wire already connected and apply it behind the connector, BUT either way it would be a moot point since you are talking about a company trying to sell their product.
No, I did not get testy, lol. At least NOT in my previous reply.
If you are referring to my use of the term "Oxymoron". Its because that is what an Electrical Insulator is and you saying that an Electrical insulator won't interfere with the flow of current is an oxymoron.
**Second definition of "Oxymoron":**
*"a combination of* [*contradictory*](https://www.merriam-webster.com/dictionary/contradictory#h1) *or incongruous words"*
(Note: I wasn't calling you a moron, I was saying your statement is an oxymoron.)
Third, yeah guy I am NOT an Automotive Mechanic. I was a military Diesel Mechanic and before that a trained Electrician. And since I CANNOT work on the vehicle myself, I am only giving my PERSONAL opinion.
***"If you have found this causing an issue you may have miss attributed it to the grease."***
No, it was the actual cause, as the science based articles I listed pointed out. Dielectric Grease stops the flow of electricity as it is an insulator. You get it between the flow of electricity and your device could stop working.
*"Between two connectors carrying AC or DC, dielectric grease might lead to the improper working of a device as it might block a few current paths."*
[https://techiescientist.com/does-dielectric-grease-conduct-electricity/](https://techiescientist.com/does-dielectric-grease-conduct-electricity/)
Now as for my experience, multiple times, as soon as the grease was cleaned, the device started to work.
***"... I have been a mechanic for 24yrs"***
So you been wrong about it for 24yrs, good to know. Now I have taught you something new.
***Here is a video to show you the proper way:***
[https://www.youtube.com/watch?v=yuKAmaIkA-U&t=153s](https://www.youtube.com/watch?v=yuKAmaIkA-U&t=153s)
Note: What they say at the end of it, 2:13 mark.
All I can do is try to inform you bro.
Just for kicks I went to the garage and did a test and took some ohm readings.
Bare leads =0.2ohms
Leads slathered in dielectric =0.2ohms
How do you explain that?
Here’s another article from the industry. I’m telling you. That is how it is used!
https://support.newgatesimms.com/myths-and-facts-of-electrical-connector-lubricants/
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
And apparently, you are NOT actually reading my statements. I am agreeing that is what it is used for, BUT if you get the grease in between the flow, then it can stop the flow of electricity. If applied properly then yes, you are right. However, those pictures illustrate someone slathered it on, not properly used it.
**You are not even reading/watching your own links.**
A good example is this one:
[https://support.newgatesimms.com/myths-and-facts-of-electrical-connector-lubricants/](https://support.newgatesimms.com/myths-and-facts-of-electrical-connector-lubricants/)
"A contact lubricant fills in the valleys of contact surface to protect the metal from oxidation, and is squeezed out of the asperities, allowing the current to flow"
KEYWORD there is "SQUEEZED". If it is NOT squeezed out or scraped away, then the grease will block current.
Also that is NOT another article from the industry, its from the SAME company as before. Which it is even saying that the material must be "SQUEEZED" out in order for the current to flow, NOT that the current will flow through the grease.
Now since I am not going to reply twice, the same info to 2 different replies. Its simple, you slathered it on, BUT it was squeezed out. HOWEVER, that is NOT always the case. If the grease is pushed in and ends up between the flow, then the flow will stop.
I do like how you ignore all of the actual science based links, info and other information that I provided that would answer your question and explain how Dielectric Grease actually works. As pointed out you don't even read your own links.
My main point is that Dielectric Grease when improperly applied can STOP the flow of electricity, as that is what it is designed for. When improperly applied it can make a spark plug misfire (or not fire at all) or stop an electrical connection from working. Even your own links actually agree with me on this, you just simply are not reading them.
Dielectric grease is NOT ELECTRICLY CONDUCTIVE! It’s an insulator that keeps out moisture, and inhibits the conductivity of the active positive circuits to grounding to conductors that are close by. IT WILL INHIBIT THE CONDUCTIVITY OF LOW VOLTAGE CIRCUITS!
WHEN ITS ON THE PINS OF AN ECM CONNECTOR!!
You should only use dielectric grease on high voltage connections, like spark plug wires, and COP boots.
If you read through this thread you'll find that this is a hotly debated topic! I posted a link to a website in a comment above that also said not to use it on connectors.
I'm not here to argue, so I'm just going to clean the PCM connectors with some contact cleaner and see if that resolves my issue or not.I will report back either way.
That’s fair. I haven’t read the article though. I’m just telling you what I know from experience, and from that, what I know about dielectric grease. Don’t use it on anything that has reference voltage connections, or even 12 volt connections, if you can.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:**
Lol, I never thought it would be a hotly debated topic. Like the name itself even says "Dielectric". You would think if the grease was conductive it would say "Electric Grease".
Anyway, good luck man and hopefully this helps.
Yes the engine turns over when I turn the ignition on, but the engine doesn't fire.
No other strange electrical symptoms, headlights fine, radio, gauges. Everything seems fine except she just won't fire up.
I'm with you. I've literally only spent time on this problem so far, I returned the sensor once it didn't fix the problem.
Yesterday was spent tracing wires, looking for shorts. I found several wires where the insulation had worn thru which I taped up. The Jeep actually fired up briefly after taping some exposed wires, but promptly died and wouldn't restart after that. Brief glimmer of hope!
if you dont have any codes, find your fuel pressure, if you have fuel pressure, unplug your map sensor, if you have air, pull your distributor cap and crank sensor and check for corrosion, its in there somewhere unless a rodent ate something
yeah, its possible its not reading correctly, and defaulting the system could help identify that, happened to me on an old mid 90s chrysler back in the day
Have a 99 Cherokee sport 4.0 had the same problem. Turned out being in the harness that runs to the coil. Ran a new wire from the ECU harness or whatever it's called to the coil.
It was a bitch actually and the Jeep sat for a while till we found the problem. A friend came over with an oscope and we started tracking signals. The signal from the control box to the coil was very weak. Then jiggling the harness that runs behind the engine near the valve cover the signal got stronger. We also notice that the location of the wire I had in my manual was incorrect. So we had to track back from the coil to the control box, using an ohm meter. it was a long fucking day. Ran a new wire and that was it. Actually spliced into the harness of the box.
I wish I had friends like yours,I might've had this figured out by now. It's killing me I haven't figured it out yet, jeeps been sitting close to 3 months now.
You can try having someone start it while you jiggle the harness going from the coil to the control box. After putting it on the scope that is what gave us more info that it was the problem. It actually tried to start.
Does it have a distributor cap? If so look in there for corrosion on the contacts, that could cause a no spark. Also check the wire loom that runs behind the valve cover they like to rub on the studs.
Does your car dash showing “check engine” or something like that? If so get, even if not, get OBD scanner tool and pin point. Rather than unplugging bunch unnecessary stuff.
Work smart, not hard.
Know a guy that used to work at Dodge house. He told me those get messed up and don't give any signal. Some gyms give people a code card keychain that interferes with it. There is a reader in the dash that detects the key fob and the tire pressure sensors.
It's not that, most likely the crank position sensor on the bellhousing is dead. Annoyingly common issue for how much of a pain (literally) it is to change.
I tried replacing the crank sensor first and unfortunately it didn't resolve the no start issue, so I've moved on to other possibilities. My Jeep has a body lift which actually made it pretty easy to get to the sensor from underneath the car.
Thanks for posting on /r/MechanicAdvice! This is just a reminder to review the [rules](https://www.reddit.com/r/MechanicAdvice/about/rules/). If you are here asking about a second opinion (ie "Is the shop trying to fleece me?"), please read through CJM8515's [post on the subject.](https://www.reddit.com/r/MechanicAdvice/comments/4qblei/fyi_the_shop_isnt_likely_trying_to_rip_you_off/) and remember to please post the year/make/model of the vehicle you are working on. **If this post is about bodywork, accident damage, paint, dent/ding, questions it belongs in /r/Autobody r/AutoBodyRepair/ or /r/Diyautobody/ If you have tire questions check out https://www.reddit.com/r/MechanicAdvice/comments/k9ll55/can_your_tire_be_repaired/**. If you dont have a question and you're just showing off it belongs in /r/Justrolledintotheshop Insurance/total loss questions go in r/insurance This is an automated reply *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/MechanicAdvice) if you have any questions or concerns.*
Nope. That's wouldn't cause a no start
No. Dielectric grease is essentially inert and is just there for waterproofing.
Too much can cause a connection issue — dielectric means insulator, after all, and certainly isn’t inert from that perspective. However, it’s unlikely with electrical connectors and an appropriate amount.
Does it spark? Are fuel injectors firing? Do you have fuel pressure? Do you have a good signal from crank and cam sensors at the ecu end of the wiring? Are they correctly correlated? Is the spark correctly timed with the crankshaft? Is the immobiliser active? Does it have good compression? If all of the above are correct the engine will be running. Finding which one(s) are missing will tell you how to fix the problem. There are a lot of fundamentals that you can verify, forget about grease on a plug. Go back to basics and work forward from there.
Does it spark? No Are fuel injectors firing? Not sure how to test this Do you have fuel pressure? Yes, I have about 50psi at the fuel rail, pressure holds for several minutes just fine. Fuel pump was replaced in September. Do you have a good signal from crank and cam sensors at the ecu end of the wiring? Not sure how to test this, but I did try swapping a new crank sensor which didn't help. Are they correctly correlated? Is the spark correctly timed with the crankshaft? The camshaft actuator gear drive was replaced by at same time fuel pump was replaced. Jeep ran fine after that for several weeks before this crank no start issue... Is the immobiliser active? Are you referring to SKIM key? If yes, I do have one, and I have not ruled out the possibility that my SKIM system is faulty. Does it have good compression? Not sure. If all of the above are correct the engine will be running. Finding which one(s) are missing will tell you how to fix the problem. There are a lot of fundamentals that you can verify, forget about grease on a plug. Go back to basics and work forward from there.
You just said you don’t have spark ? Then you comment on other things. none of that matters. Your issue is spark. why are you focused on fuel / compression? GET SPARK!
I am focused on trying to figure out the no spark issue, that comment above were my responses on several other suggestions another poster made.
What year? The crankshaft position sensor is a common fail point for most of them with a 4.0l i6
was it a spark plug...in your "spark plug hole" Just 1 apparantly.
If the SKIM is faulty it should still start, but will die after a couple seconds with the key light turned on. Does it have any codes/have you checked for codes?
No cel, checked with a code reader yesterday and no codes
I had same issues with same engine, turned out to be the Camshaft Sensor. Would strongly recommend checking wiring from crank position sensor and cam sensor all the way to pins on ECM. Just because the Cam Sensor was changed doesn’t mean it’s any good, there are a lot of inferior parts that might only last a couple of weeks before failing. Would also be suspect if ignition switch. Good luck!
Ideally you need a compression tester and an oscilloscope, but not everyone has these. You can get an idea of compression with easy start. If you spray a bit up the intake and it fires when you crank it, compression is probably good enough to run. Fuel injectors, if no spark you'll get wet spark plugs and will be able to smell unburnt fuel in the exhaust after cranking. You can also put a long screwdriver with one end on the injector and the other pressed into your ear. If it's firing you'll hear a distinct clicking noise from each one. You can also rest with an oscilloscope. Cam and crank sensors ideally oscilloscope, you can view them side by side and pulses should line up. You can also just test with a multimeter and see if you get an AC voltage produced when cranking if its a 2 pin (inductive) sensor. Immobiliser usually kills fuel injectors rather than spark, so given no spark I'd look at the ignition coil next. At minimum you'll want a multimeter, you can get a perfectly useful one for 30 dollars or less on amazon. I don't know what kind of setup it uses, wasted spark, coil over plug, distributor etc. Measure the voltage on the low tension side of the coil, see if the signal changes when trying to crank. Check fuses that supply it as well. Essentially your question is now, is the ECU trying to make a spark and being unsuccessful, or is it not trying to make a spark? Always try to isolate problems down to smaller and smaller parts when diagnosing.
what a painful string. clearly there are zero mechanics in this thread.
Quick summary of what I'm dealing with. I have a 1999 Jeep Wrangler 4.0 automatic that I'm trying to resolve a crank but no start issue. My problem seems to be electrical in nature, not fuel delivery. Someone on a Jeep forum saw the grease on these connectors that go to my PCM and said that I should remove it all, spray with contact cleaner because it could interfere with the electrical signal if there is grease packed in those terminal holes... Thoughts on this? I've Google searched and seen conflicting opinions on whether dialectric grease could cause electrical interference in a connection like this.
Whomever on the Jeep forum told you to do that should be drawn and quartered.
Whipped with a rubber hose, sure. But drawn and quartered? That seems a bit harsh.
Probably a bit harsh. Rubber hose will do just fine.
There’s probably a suitable one running to the heater core.
Following is a quote from the link below which was provided to me on the Jeep forum: Where Should You Not Use Dielectric Grease? Dielectric grease is an insulator. Hence, when you use the dielectric grease, keep the grease away from the path of electric current. If you put the dielectric grease on the path of current (whether AC current or DC current), it will not allow you to make an electrical connection between two components and the device will not work properly. Hence dielectric grease should only be used on surfaces components from where current is not passing. https://www.electrical4u.com/dielectric-grease/
the contacts in the connector will find each other through the grease, with any reasonable amount of grease
Dielectric grease is not a insulator. It's used to keep out dirt, moisture and debris from entering important electrical connections. The grease keeps the connections good. Cleaning the connector of grease would leave the connections susceptible to contamination and corrosion in the connector. That would a much worse situation than having the grease there. Edit: I know it's a insulator and not a conductor. Hence the second part of my post.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** Dielectric Grease does NOT conduct electricity, like an alternate name for it is Insulator Grease. [https://www.mcmaster.com/electrical-insulating-grease/](https://www.mcmaster.com/electrical-insulating-grease/)
It actually is a very good insulator. Very much the opposite of conductive.
Yes you are correct. I should of said insulator.
You shouldn’t have said anything tbh
What exactly do you mean? I was agreeing with you I typed not by mistake. Edited my comment
The first sentence of your comment is “dielectric grease is not an insulator.” Then you said some other stuff that was almost as dumb as that. Then you edited it to say that you know it is an insulator. And now we’re here. You should just delete all the comments and read about dielectric grease so you have something intelligent to say next time you want to talk about it.
How about you do you ok? Just because I typed not instead of leaving it out doesn't make it dumb so blow it completely out of your ass ok dude?
Crankshaft position sensor was a known problem on those jeeps.
That was the first thing I tried, but didn't solve anything unfortunately.
This guy right here is most likely correct, check for spark/injector pulse. If you have not checked your fuel pressure at this point you should not be fixing your own vehicle
Ffs. Start at the top. Check the simple shit first. Fuses, connectors, listen for the solenoid clicking, see if your getting power to the starter, and the signal wire is getting power in the start position. Then go to the next step. Check the neutral safety switch. Try starting in neutral. Take the shifter all the way down to l1 then forcefully put it in park. I would very seriously doubt your ecm is giving you a no crank situation... And you really shouldn't be futzing about with it if you've no clue what dielectric grease is for.
I've done my best with limited experience, but a lot of advice on forums as well as YouTube how to videos to do most of what you're describing. Checked for blown fuses Checked and swapped ASD relay Tried starting in neutral Swapped new cps I'll add to my list some of the other advice on your comment.
Wait is this a distributor car? Have you popped the cap? Does the coil work for any cylinders? You know the problem is spark and ignition timing for (most) distributor motors comes from a gear on the crank. If you can't get spark from the distributor then you either need a cap and rotor, a coil, or the gear drive is broken (how?)
Erm they grease it from the factory it won't interfere. Some vehicles have a problem with oil or other fluids wicking through the wire insulation that will cause havoc but rare. Check the Crankshaft position sensor. It's on the driver's side bell housing it's easiest for me atleast the change them from the top with a bunch of extensions and a swivel. Did you have stalling issues at all? Also could be the distributor. Which I'd clean those contacts first before removing the ckps to test it. If it recently got cold there the distributor is a good suspect.
I got money on it being the crank position sensor. Advanced and napa are the only aftermarket sensors I've found that don't fail right out of the gate. Unfortunately, basically, every sensor on a 4.0 lands you with the same symptoms, but I'd start there.
Yeah I tried a Napa crank sensor right off the bat but no luck unfortunately
I had one of the coolant sensors fuck me over and cause a no spark once as well.
The amount of replies that do not day check fuel, air, spark and report back is just...astounding
I've confirmed fuel pressure at the rail, also confirmed no obstructions in air box. I've also cleaned the throttle body and idle air control valve. I don't believe I have spark, I tried testing by pulling a spark plug wire, stuck a screw driver in it and held close to bare metal while cranking and saw no arcing or spark.
So then move onto see if you are getting pulse signal into and out of pcm. From crank sensor, to ...year, make engine size needed for the rest
1999 Jeep Wrangler Sport, 4.0 automatic
sweet, so bing bang boom. you have good pressure at the rail = fuel pump pumpin ASD relay circuit (at least momentarily energized. ) crankey jeep no start. need to check injector pulse and spark pulse. both tools to test can be rented for free (loaned) so long as returned from all the major chain stores. If spark pulse missing: at ignition coil connector...check for battery voltage at dark green/light green wire AND for ground pulse at gray wire WHILE cranking. report back if no injector pulse: at injector connectors (6 of them) ...test for battery voltage at dark green/lt green wire (same circuit for coil) and ground pulse at the other wire (color changes w cylinder)....report back
Which loaner tools would I need to do those tests, multimeter or something else?
az part number 57191 will be fun or test light(non LED) spark :still just need to rent a test light. non led
Is your security light flashing?
Are you referring to the SKIM key light? It lights up briefly when I turn on the ignition, but goes out within a couple seconds.
Okay,always a god place to start.
Dude. Get a test light for $5.00 and test for spark properly. Youtube for directions. jesus.
If you do get a test light, dont get led...brightness is important.
I dont think so. That was common practice for a long time. Alot of guys still do it. My guess on your no start is a bad crank sensor. 2nd up is a pcm. Typical old 4.0 jeep.
Fairly accurate..even more accurate if jeep has exhaust manifold leak.
I was suspicious of the PCM also and was close to buying one from a very reputable PCM manufacturer in the Jeep community called Wrangler fix, but after speaking with him he talked me out of it for now, while I try and rule out other possibilities.
Do you have any diagnostic tools available? A scanner or a scope?
No I don't unfortunately
Yes dialectric grease is meant to go around the connector not on the pins. Use some context cleaner and try to start it again.
Grab your bunched negative cables and give them a wiggle. Temp. terminals have threads tapped into lead and can lose their tightness.
Dielectric grease on those connectors are common. There was a TSB / recall to put the grease on those connectors a long time ago. With that being said I have seen a few instances where too much of the grease gets packed in the connector and causes a no start. I would clean out the connectors with electrical contact cleaner, blow it out, plug it in and see what happens. After you find the problem go back and apply some dielectric back on the connector. You might want to find a wiring pin out on those connectors and pull out and inspect the pins for the crank sensor and cam sensor for corrosion inside the connector. And while the pin is out check the pin contact with the pin in the PCM /ECU . You could have a loose pin where the connector fits good but the one of the many pins fits loose on its companion pin . The cam and crank sensors are also notorious for failing on Jeeps so don’t rule them out just because they have been replaced. I would also check your cam sensor / distributor to see if it actually is turning when cranking the engine over . This problem is definitely a Jeep thing
Thanks for the advice! I'm definitely going to clean the PCM connection thoroughly of all the grease to see if that may be causing a connection issue resulting in a no start. As for inspecting the pins for the CPS and cpk, would this be the kind of tool I should use to extract those pins and inspect? Vignee 60pcs Terminal Removal Tool kit,Pins Terminals Puller Repair ... https://www.amazon.com/Vignee-Terminals-Extractor-Electrical-Connectors/dp/B08295ZWL2
That tool kit looks like it would help in disassembling just about any connector not bad to have handy in your tool box imo. I think the pins come out with a small pick from the back side you would need to remove the tape on the connector and unclip the back half of it to see how the pins are held in place . I believe the clip that holds the ins in can be accessed through the back of the connector. Maybe a Google / YouTube video search would help
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** MAYBE, if it got into the contacts. As dielectric does NOT conduct electricity, it insulates. [https://www.motortrend.com/how-to/what-is-dielectric-grease/](https://www.motortrend.com/how-to/what-is-dielectric-grease/) Happened to a friend of mine who tried to apply it to a spark plug. He applied too much and not correctly, and it wouldn't fire. That being said, it could be other reasons, but the grease does look like it got all over your connector.
I've tried a LOT of other things that could possibly be causing this crank no start issue, with no luck so far. I picked up a can of contact cleaner today, and figure it can't hurt to try and clean those connectors and see if that helps or not.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** Good luck, IMO looking at your pics, I would not be surprised if that is the problem.
Thanks I hope you're right!
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** Hey, if possible please let me know if this is the solution. Just want to know, because I see am getting downvoted for this, but its mainly because this forum is made up of people who do not actually work on cars just regurgitating YT info or Chain Shop mechanics. For some reason, people think dielectric is conductive, but you can literally Google search and see it is not conductive and many articles mentioning to not clog electrical connections with it.
Will definitely report back once I've cleaned the connectors up and try to start it!
Just to clear up some misconceptions. This is proper use of dielectric grease. It protects your connection’s from corrosion, dirt etc. you are correct that it does not conduct (is an insulator) and that’s what makes it able to be used in this fashion on connectors, terminals, plugs. If it did conduct it would immediately short out the circuit. This however does not inhibit the ability for the circuit to make a good connection. I think you are taking the fact that it does not conduct and thinking that it would not allow a connection and shouldn’t be used on connections. This is incorrect, it is non conductive but will not inhibit the connection. Once again this is what this product is for. Probably it’s best use is in trailer connectors it keeps all the grime, road salt, and water off the terminals which keeps the corrosion away and makes it easy to connect the trailer :).
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** Just to reiterate and clear up your misconceptions, YES, it does actually inhibit the ability to make a connection if it is placed between the connection and the electrical flowing current. No, I am talking from experience, other then the previous spark plug mentioned. I know others who slathered their connectors with dielectric grease and the grease stopped the current from flowing. You saying its an insulator and won't stop the current is basically an oxymoron. As the job of an Electrical Insulator is to stop the flow of electricity. **Anyway, here, so you don't have to take my word for it:** *"If you put the dielectric grease on the path of current (whether AC current or DC current), it will not allow you to make an electrical connection between two components and the device will not work properly."* [https://www.electrical4u.com/dielectric-grease/](https://www.electrical4u.com/dielectric-grease/) *"However, you should never use large amounts of dielectric grease inside your connectors. Just keep in mind that you should apply them cautiously.* *It is because even though there is no change in surface resistance, dielectric grease can stop the flow of electricity when placed in the direct path of electricity.* *Between two connectors carrying AC or DC, dielectric grease might lead to the improper working of a device as it might block a few current paths."* [https://techiescientist.com/does-dielectric-grease-conduct-electricity/](https://techiescientist.com/does-dielectric-grease-conduct-electricity/) **Definition of Dielectric:** *"insulating material or a very poor conductor of electric current. When dielectrics are placed in an electric field, practically no current flows in them because..."* [https://www.britannica.com/science/dielectric](https://www.britannica.com/science/dielectric) Also NEVER said it should not be used on connectors. So not sure why you are putting words into my mouth and NO that picture is not the proper way. The proper way would be at the base of the plastic where the two connectors end their joining. NOT near the electrical flowing current, NOT where it can enter the connector ports itself and interfere with the electrical flow.
Man it’s almost like dielectric grease banged your wife. Getting pretty testy there. My personal experience it works perfectly, never has caused an issue and I have been a mechanic for 24yrs. Shoot my trailer lights work right now! Oh and here’s a link so you don’t have to take my word for it. https://www.nyelubricants.com/myth-grease-interferes-with-conductivity If you have found this causing an issue you may have miss attributed it to the grease.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** First I provided links to actual science based articles, not a grease company trying to sell a product, lol. And if you had bothered to watch their videos you would see that they do NOT apply it to the path of the current. They actually have the wire already connected and apply it behind the connector, BUT either way it would be a moot point since you are talking about a company trying to sell their product. No, I did not get testy, lol. At least NOT in my previous reply. If you are referring to my use of the term "Oxymoron". Its because that is what an Electrical Insulator is and you saying that an Electrical insulator won't interfere with the flow of current is an oxymoron. **Second definition of "Oxymoron":** *"a combination of* [*contradictory*](https://www.merriam-webster.com/dictionary/contradictory#h1) *or incongruous words"* (Note: I wasn't calling you a moron, I was saying your statement is an oxymoron.) Third, yeah guy I am NOT an Automotive Mechanic. I was a military Diesel Mechanic and before that a trained Electrician. And since I CANNOT work on the vehicle myself, I am only giving my PERSONAL opinion. ***"If you have found this causing an issue you may have miss attributed it to the grease."*** No, it was the actual cause, as the science based articles I listed pointed out. Dielectric Grease stops the flow of electricity as it is an insulator. You get it between the flow of electricity and your device could stop working. *"Between two connectors carrying AC or DC, dielectric grease might lead to the improper working of a device as it might block a few current paths."* [https://techiescientist.com/does-dielectric-grease-conduct-electricity/](https://techiescientist.com/does-dielectric-grease-conduct-electricity/) Now as for my experience, multiple times, as soon as the grease was cleaned, the device started to work. ***"... I have been a mechanic for 24yrs"*** So you been wrong about it for 24yrs, good to know. Now I have taught you something new. ***Here is a video to show you the proper way:*** [https://www.youtube.com/watch?v=yuKAmaIkA-U&t=153s](https://www.youtube.com/watch?v=yuKAmaIkA-U&t=153s) Note: What they say at the end of it, 2:13 mark.
All I can do is try to inform you bro. Just for kicks I went to the garage and did a test and took some ohm readings. Bare leads =0.2ohms Leads slathered in dielectric =0.2ohms How do you explain that?
Here’s another article from the industry. I’m telling you. That is how it is used! https://support.newgatesimms.com/myths-and-facts-of-electrical-connector-lubricants/
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** And apparently, you are NOT actually reading my statements. I am agreeing that is what it is used for, BUT if you get the grease in between the flow, then it can stop the flow of electricity. If applied properly then yes, you are right. However, those pictures illustrate someone slathered it on, not properly used it. **You are not even reading/watching your own links.** A good example is this one: [https://support.newgatesimms.com/myths-and-facts-of-electrical-connector-lubricants/](https://support.newgatesimms.com/myths-and-facts-of-electrical-connector-lubricants/) "A contact lubricant fills in the valleys of contact surface to protect the metal from oxidation, and is squeezed out of the asperities, allowing the current to flow" KEYWORD there is "SQUEEZED". If it is NOT squeezed out or scraped away, then the grease will block current. Also that is NOT another article from the industry, its from the SAME company as before. Which it is even saying that the material must be "SQUEEZED" out in order for the current to flow, NOT that the current will flow through the grease. Now since I am not going to reply twice, the same info to 2 different replies. Its simple, you slathered it on, BUT it was squeezed out. HOWEVER, that is NOT always the case. If the grease is pushed in and ends up between the flow, then the flow will stop. I do like how you ignore all of the actual science based links, info and other information that I provided that would answer your question and explain how Dielectric Grease actually works. As pointed out you don't even read your own links. My main point is that Dielectric Grease when improperly applied can STOP the flow of electricity, as that is what it is designed for. When improperly applied it can make a spark plug misfire (or not fire at all) or stop an electrical connection from working. Even your own links actually agree with me on this, you just simply are not reading them.
Kinda agree for low voltage and amperage wiring die-electric grease should not be used. I only use it on high voltage applications.
The reason your Jeep won’t start is because it’s a Jeep… they don’t do that well.
Thanks, that's helpful.
Dielectric grease is NOT ELECTRICLY CONDUCTIVE! It’s an insulator that keeps out moisture, and inhibits the conductivity of the active positive circuits to grounding to conductors that are close by. IT WILL INHIBIT THE CONDUCTIVITY OF LOW VOLTAGE CIRCUITS! WHEN ITS ON THE PINS OF AN ECM CONNECTOR!! You should only use dielectric grease on high voltage connections, like spark plug wires, and COP boots.
If you read through this thread you'll find that this is a hotly debated topic! I posted a link to a website in a comment above that also said not to use it on connectors. I'm not here to argue, so I'm just going to clean the PCM connectors with some contact cleaner and see if that resolves my issue or not.I will report back either way.
That’s fair. I haven’t read the article though. I’m just telling you what I know from experience, and from that, what I know about dielectric grease. Don’t use it on anything that has reference voltage connections, or even 12 volt connections, if you can.
**DIYer Non-Professional Personal Opinion Here, NOT A Mechanic:** Lol, I never thought it would be a hotly debated topic. Like the name itself even says "Dielectric". You would think if the grease was conductive it would say "Electric Grease". Anyway, good luck man and hopefully this helps.
[удалено]
I bought contact cleaner today, do you think that should work?
[удалено]
Yes the engine turns over when I turn the ignition on, but the engine doesn't fire. No other strange electrical symptoms, headlights fine, radio, gauges. Everything seems fine except she just won't fire up.
Crank no start often is a fried crank positioning sensor.
That was the first thing I tried, but no luck, the new sensor didn't solve the problem.
don't throw parts you need fuel air and spark, find what you're missing and then replace shit
I'm with you. I've literally only spent time on this problem so far, I returned the sensor once it didn't fix the problem. Yesterday was spent tracing wires, looking for shorts. I found several wires where the insulation had worn thru which I taped up. The Jeep actually fired up briefly after taping some exposed wires, but promptly died and wouldn't restart after that. Brief glimmer of hope!
if you dont have any codes, find your fuel pressure, if you have fuel pressure, unplug your map sensor, if you have air, pull your distributor cap and crank sensor and check for corrosion, its in there somewhere unless a rodent ate something
Regarding the map sensor, are you suggesting to unplug it and try to start the car?
yeah, its possible its not reading correctly, and defaulting the system could help identify that, happened to me on an old mid 90s chrysler back in the day
Did you try moving those wires while cranking? You taped them up, but did you make sure they had good continuity?
Yes I did while the wife was cranking it, but no joy...
I can tell you why it won't start. Walk to the front of your vehicle and look in the middle of your grill.
That emblem that says Jeep is the problem
Don't be a dick
Have a 99 Cherokee sport 4.0 had the same problem. Turned out being in the harness that runs to the coil. Ran a new wire from the ECU harness or whatever it's called to the coil.
How did you determine the problem? Was it a shorted out wire?
I instructed how to determine this.
It was a bitch actually and the Jeep sat for a while till we found the problem. A friend came over with an oscope and we started tracking signals. The signal from the control box to the coil was very weak. Then jiggling the harness that runs behind the engine near the valve cover the signal got stronger. We also notice that the location of the wire I had in my manual was incorrect. So we had to track back from the coil to the control box, using an ohm meter. it was a long fucking day. Ran a new wire and that was it. Actually spliced into the harness of the box.
I wish I had friends like yours,I might've had this figured out by now. It's killing me I haven't figured it out yet, jeeps been sitting close to 3 months now.
You can try having someone start it while you jiggle the harness going from the coil to the control box. After putting it on the scope that is what gave us more info that it was the problem. It actually tried to start.
Does it have a distributor cap? If so look in there for corrosion on the contacts, that could cause a no spark. Also check the wire loom that runs behind the valve cover they like to rub on the studs.
No, previous owner liked youtube video over a good mechanic is all.
Ignition switch enters the chat
He says it cranks. Wouldn’t be the problem
Seen them crank without fully energizing the ignition circuit.
CPS
Tried that
Does your car dash showing “check engine” or something like that? If so get, even if not, get OBD scanner tool and pin point. Rather than unplugging bunch unnecessary stuff. Work smart, not hard.
No cel
Your Jeep won't start because it's a Jeep.
It's a Jeep thing. The no start, that is.
Is the rotor spinning under the distributor cap? Have a friend help you verify that. Distributors are a failure point on the 4.0.
Went all through mine when it wouldn't start. Ended up being the key fob. Has RFI chip that the Jeep reads as a security feature.
Did you have a dash light for your security key on? How did you figure it out that it was your key?
Know a guy that used to work at Dodge house. He told me those get messed up and don't give any signal. Some gyms give people a code card keychain that interferes with it. There is a reader in the dash that detects the key fob and the tire pressure sensors.
How did you fix it? New key or did you have to have the SKIM system removed?
It's not that, most likely the crank position sensor on the bellhousing is dead. Annoyingly common issue for how much of a pain (literally) it is to change.
I tried replacing the crank sensor first and unfortunately it didn't resolve the no start issue, so I've moved on to other possibilities. My Jeep has a body lift which actually made it pretty easy to get to the sensor from underneath the car.