Hello, I have been trying to deal with this intermittent problem since September, and recently the problem is starting to happen almost on a daily basis and is quite literally ruining my life. Sorry if this post is kind of long, I just want to include as much relevant information as possible as even mechanics have been unable to diagnose this problem.

1991 Cherokee Limited 4.0 4x4 Automatic 130,000 miles

The problem: Intermittent crank and start then stall. Engine will start like normal then cut off after .5 seconds, before it has a chance to actually idle. At first pressing the gas had no effect as it started. Within the past couple days, if I press the gas pedal the RPM's have started to rev a little higher before cutting off. Using a wire to jump the fuel pump relay also doesn't help. Problem goes away after waiting a few hours or so. Recently this has become an almost daily occurrence

Things I have done to fix this problem: New fuel pump ballast resistor, new ignition coil, 4 different crank position sensors (including mopar), new throttle position sensor, cleaned iac valve, new duralast gold battery, cleaned engine grounds, bosch 4 point injectors (4000 miles ago), spark plugs rotor and distributor cap 9000 miles ago

One morning back in September I woke up and tried to start the Jeep up to drive to work. I turned the key and the engine started up like normal, but before the RPMs even had a chance to stabilize after startup, the engine just cut off as if someone removed the key. Trying to start it again will result in either the starter cranking forever, or the engine starting and stalling again (about a 50/50 split between just cranking and start/stall). After 30 minutes of trying to get the Jeep started I decided to call AAA to get a tow back home. After doing some searching I became convinced that the crankshaft position sensor was the culprit, so I bought one from Autozone which seemed to solve the problem. It was probably 2 or 3 weeks before this problem came back, at which point I get the cps replaced for free under warranty. Some time later the problem came back again, so I bought a new old stock Mopar cps on ebay and still the problem came back.

Then I became convinced that the problem was with the fuel pump, but the pressure at the pump and the rail were good, and I can hear it prime every time I turn the key. The Jeep will also start and drive normally whenever the problem is not happening, although sometimes in the morning you have to keep the key twisted a little longer and press the gas a little bit. I even went offroading for the first time in the desert on New Years Day for 6 hours without shutting the engine off due to fear of it not starting back up again, and it performed beautifully. For this reason I don't think it is a problem with the fuel pump, but what do I know.

Last week the problem came back while I was at the beach and I had it towed to a mechanic. Of course they were closing by the time the Jeep got to them, and by the time they got a chance to look at it in the morning the problem went away again, only to come back the same night I got it back from the mechanic. Mechanic said every time the tried to start it it started right up, all the sensor had the proper readings and he couldn't find anything wrong with the wiring harness. I desperately need help with this as my Jeep is currently my only source of income as I do grocery delivery work with it.

Someone sent me a video by Bleepin Jeep on YouTube in which he has an XJ that is experiencing the exact same problem as mine. In the video he replaces the fuel pump ballast resistor which made me super hopeful that a new ballast resistor would solve the problem, but it did not. Here's a link to that video in case you want to watch it, it has a perfect representation of my problem

 

Lets start first with the obvious parts.... Have you checked the power source for your flux capacitor?
You're probably going to get some people to ask you to break that long post down into smaller posts so they can be addressed a little easier... and talked about 1 at a time to rule out suspect parts....

And a huge thank you for using punctuation and capital letters where required so us old guys can understand it better hahaha.... some people post up something as long as your post and wont have a single capital letter or any punctuation....

 

What about the starter itself? Or, maybe even the neutral safety switch?

The pump can still work and still be faulty at the same time...

 

ECM acting up?
Neutral safety switch?

 

I haven't investigated the starter at all, I'm a super noob when it comes to any kind of car repair stuff, in my mind since the engine was actually starting I excluded the starter as a possibility but I will pull it later today and see if I can find anything wrong with it.

In regards to the neutral safety switch, I removed and cleaned it in August 2019 when I was chasing another issue that turned out to be a dead battery that wouldn't hold a charge. Maybe I'll pull that off again and check it out

 

I tried to clear the ecm last night by removing the positive cable and grounding it on the negative, then reconnecting the positive cable and messing with the headlights, but as soon as I reconnect the positive battery cable the security system starts going off. Thankfully it only flashes the headlights and doesn't beep the horn. Cleaned the NSS August 2019 but haven't messed with it since then

 

Did you disco the negative side before you touched the positive side to it? I wouldn't think it matters though..... But... the amount of time the 2 cables were touching might matter....
I have done it where I disco both cables from the battery and connect the ends of the cables together with zip ties or some metal wire, and leave it for a little while to give everything time to discharge (capacitors and stuff)

 

I left the negative cable attached and used a wrench to ground the disconnected positive cable to the connected negative cable for 30 seconds, then I reconnected the positive and attempted to flash the headlights, but the security system was going off so it didn't have any effect. Should I turn the headlights on and off before reconnecting the positive battery cable?

 

That sounds like a good idea to me that way it discharges any stray voltage.... I thought you said you were rookie at this hahaha.... Sounds like you know a little bit about electrical theory at least!!

 

Security system? Like engine immobiliser?
WHEN it starts up, does it cut out after the same amount of time, every time? Or does is it sometimes manage to stay on a bit longer and than die?

Does your year have an ASD relay?
IN past at some point had random no starts, cutting out after starting up, which were cured by changing out the ASD relay, which was deemed to be not the cause.

 

what about the fuel pump? Are you getting correct psi at the rail after she starts up? That's pretty easy to check.
Remember basics so you don't miss anything and feel like a dork later.... what does any internal combustion engine need to run?.... Fuel, Air, Spark. (each at the right time) Track down each one and you'll find the issue. Don't panic, it's not rocket science

 

IAC cleaned. How about the throttle body itself? Normal maintenance

 

When your vehicle stalls, does the vehicle throw any codes? Obviously something is triggering the stall after start up.

https://www.cherokeeforum.com/f2/dia...de-list-78108/

how to pull codes
https://www.quadratec.com/jeep_knowl...article-24.htm

 

How is this issue going?
any answers to all the questions/suggestions yet?

 

Neutral Safety Switch??

I had similar symptoms wit my 94 XJ. I have an automatic, for the times it did not start, I would giggle the shift while in park and turn the key and it started more than 50% of the time. When the trick no longer worked, I had the neutral safety switch replaced and never had issues again.