[SLHK]

I am looking for suggestions for what I'm experiencing, and how to rectify it. Jeep is a 1999 4.0 automatic w/265K miles and completely 'stock.' It starts and runs magnificently - unless I wash it! This has happened several times and again yesterday. Even being VERY careful not to let too much hose water run into the louvers that are between the windshield and the hood - the LAST thing I'd think you'd need to be cautious of on a Jeep! - I can be sure that after a wash I'm going to have an issue. The engine will start perfectly and instantaneously, I may drive 30 seconds/100' . . . and then the engine instantly dies/shuts off. Not a stutter, or 'cough,' just instantly stops as though you disconnected the coil wire. After this happened awhile back, I was advised to clean up and pack the 3 connectors to the ECM with dielectric grease and I very carefully did so. I expected that this had solved the problem. I'd driven it quite a few times since with no issues (but never in the rain). Washed it yesterday, and allowed very little water to get through those louvers. Drove it 300' from the car wash spot to my parking spot - no issues. Came back 3 hours later to take it all shiny out on a sunset cruise. Started instantaneously, backed up, pulled to the parking lot exit 100' away, pulled onto the street, got 10' and it immediately died - right in the middle of the road - not good. Tried re-starting 4 - 5 times and not even a hint it would start. Then, the 6th time, it starts. Taking no chances, I immediately backed up back into the parking lot, and it died again. More re-start efforts and after quite a few it started. I wasted zero time to get it into a parking space whereupon it died again. Efforts to re-start - even 10 times - yielded NOTHING - not even a 'cough.' So gave up, confident that today - after sitting and I suppose 'drying out,' it would start - which it has done before and which today it did. It started just fine today and I shut it off after it ran without issue for about a minuted. I was advised it might be the TPS - Throttle Position Sensor - so I unplugged it, cleaned the connector, and packed that connection with dielectric grease. It started again without issue, and I cautiously drove it around a couple miles and all seems well. But . . . I'm not convinced I've solved the problem. It's not happened, but I fear when I drive in the rain - on the Interstate - this issue is going to occur again, and I'm going to have a really serious issue. I wanted to unplug the 2 'huge' side-by-side connectors in the 'Y' at the center of the firewall . . . but I wasn't able to get either disconnected and was afraid I was going to break them - I need to figure out the 'right' way to open them up (they have a red locking 'slide' on them, etc.), and then pack them with dielectric grease also. This because they sit right below those louvers where the water I suspect is causing the issues comes through. I don't know if these are causing an issue, but it can't hurt to clean and pack them, right? So . . . thanking anyone in advance for your thoughts on this. What is getting wet and causing this issue? Again, otherwise it runs flawlessly!

 

[Jerry Bransford]

The above is one reason I don't go along with hood louvre installs. I'd be suspicious of your crankshaft position sensor. That's one of the sensors that if something's wrong it it the engine can die instantly as it's the part that generates the engine's master timing signal. If my TJ had hood louvres I'd seal them off from the bottom to keep water out. Especially since an engine doesn't run any cooler with them despite marketing claims they do. I'd venture that 99.999% of those who install them do them solely for their looks.

 

[SLHK]

The above is one reason I don't go along with hood louvre installs. I'd be suspicious of your crankshaft position sensor. That's one of the sensors that if something's wrong it it the engine can die instantly as it's the part that generates the engine's master timing signal. If my TJ had hood louvres I'd seal them off from the bottom to keep water out. Especially since an engine doesn't run any cooler with them despite marketing claims they do. I'd venture that 99.999% of those who install them do them solely for their looks.

Again, the Jeep is 100% 'stock' - these louvers are NOT in the hood - as I stated, they are between the hood and the windshield - I'll attach a foto

 

[Old Dogger]

Welcome to the Forum!
Is the back of your hood seal missing?

 

[Jeepster20054liter]

Can you reproduce this problem for example at home spraying the hood? Does this happen every time? Has it happened in the rain? I am less a fan than some folks of diaeletic grease as it is an insulator. I tend to thing first of a contact enhancer. I would not change any parts until I had a diagnosis.

 

[Digger84]

You do realize dielectric grease is a insulator (it blocks conduction) good on gaskets of connectors and where porcelain of spark plug contacts boot and ideal inside an old points distributor where points follower contacts cam lobes of distributor shaft but does not belong on actual electrical contacts as can make conduction across contacts worse

Clean that crap off contacts
Check the engine to firewall ground
Look closely where engine harness passes near or actually contacts rear bolt top on battery hold down

Clean and tighten battery cables and look for corrosion where wires of cables enter lead battery clamp

 

[Rixthe1]

Those vents are for your heater and A/C fresh air intake. They drain onto the ground, not the engine. Start it in a very dark garage, with exhaust tubing going outdoors. If the blue sparks are dancing around your distributor cap and wires, problem solved. I recommend having a timing light handy, when it stalls, hook up the light, have someone crank it, while you watch for flash. Then if there is no flash, you will know you are on the right track. Oil and silicone grease is an insulator. Current actually flows in a magnetic field around the wire, too much insulating grease, may disrupt the flow. I have added 3 ground wires under my hood, that solved lighting, cranking and starting problems. Loose or poor ground connections get worse when they are wet.

 

[SLHK]

My sincere thanks to all for taking the time to lend your experience and opinions on this - you've put the proverbial ball in my court, and so I have some work to do, and to that, I look forward.

 

[The Good Twin]

Dude, I feel for you. Different Jeep, similar engine and similar problem. Things I'm ruling out are the ASD relay and the Fuel Pump. Reasoning is that when I place the engine to start, it tries to crank, but doesn't however when doing so and I depress the Schroeder valve on the fuel rail, I get squirtage. Things I haven't ruled out, Fuel regulator (Doesn't seem like the fuel rail is keeping pressure--a possible suspect but that wouldn't just kill the engine--it would make it run rough. Camshaft position sensor--would prevent spark. I need to pull the #1 plug and do the screwdriver test. Not sure if this would throw a code. After these checks, I'll check the wiring and the grounds. Crankshaft position sensor--if this fails, the engine will not run. This is my primary suspect and I just need to get some time to check it. Also, I haven't pulled the codes using the on-off functionality. Just need to get some time to dig in. Good luck with your trouble shooting.

 

[Digger84]

What does tries to crank but doesn’t mean
Cranking is just the starter spinning the engine crankshaft so either the engine crank spins or it does not

Now if you mean cranks briskly but does not start
Common issues are
Lack of adequate spark or lack of adequate fuel
Bad fuel
And on an old engine timing chain that jumped one or more teeth

 

[Rygreenscoots]

My JK did the same thing. It would die at stop lights. My 2011 ram as well. No codes no anything, just completely random. No stored codes. It just acted like someone turned the key off. Both times I replaced the camshaft position sensor and haven’t had the problem again.

 

[David CJ2 and TJ]

Those vents are for your heater and A/C fresh air intake. They drain onto the ground, not the engine. Start it in a very dark garage, with exhaust tubing going outdoors. If the blue sparks are dancing around your distributor cap and wires, problem solved. I recommend having a timing light handy, when it stalls, hook up the light, have someone crank it, while you watch for flash. Then if there is no flash, you will know you are on the right track. Oil and silicone grease is an insulator. Current actually flows in a magnetic field around the wire, too much insulating grease, may disrupt the flow. I have added 3 ground wires under my hood, that solved lighting, cranking and starting problems. Loose or poor ground connections get worse when they are wet.

Where did you add the 3 grounds? I am having the old issue of the instrument cluster working intermittently. I have always felt like that it is a ground issue but I have cleaned all that I can find and certainly wouldn't be opposed to adding a few more grounds. Thanks