I have a 1996 Cherokee w/ a 4.0L I6 and over the last couple of years it has been in and out of 4-5 garages because it will not stay running. My son has been driving the vehicle for the last 10yrs until this issue started. We’ve (meaning the auto shops, my son and myself) have changed the head, fuel pump, injectors, filters, sending units, ECU and a list of other parts. Ran multiple test on fuel system, electrical system but nothing seems to fix the issue.

The last shop my son took it to missed with it for awhile (2-4 months) and finally said the crank was lopping. I personally am lost so I’m asking y’all if that sounds possible. I have some maintenance experience but have never heard of this but if it could be the issue how to I fix it.

 

I've been around engines most of my life and don't understand the term "loping" for a crankshaft. Can you be more specific about "not staying running?" Does it start and shut off right away? Does it stall when coming to a stop? Does it run as long as you hold the throttle? Something is being overlooked. Most of today's mechanics are just glorified parts changers.

 

i've heard of lobing on a camshaft, but not a crankshaft. but that general meant you had large camshaft in a hot rod.

 

When you try to start the vehicle it will start then dies, will not run more than 20-30 secs

 

Sounds suspiciously like a security issue, as in alarm system, although 30 seconds is a long time for that to be it. Have you changed the ASD relay? It may be weak and not holding in when it gets warm. Likewise the fuel pump relay. The ASD relay is energized by the ECU and controls both the ignition and injector circuits, If it's not holding in, the engine will shut off just like you turned off the key. If it's the fuel pump relay, it'll stumble and stall as fuel gets burned off.

I'd hate for it to be that simple. Maybe he's saying "loping" as in running rich. What injectors did you use?

 

Thank you dave1123 will check those relays myself 👍🏻

 

Any chance of posting a complete list of what's been done? Sounds like a lot of money spent on incompetent mechanics, from what you've said.


One thing to verify - if any of the sensors were replaced, what brand was used? These things are very picky about sensors. It is not at all unusual for someone to replace the CkPS, thinking that was the problem, only to spend much more money and time replacing other components, when all the time it WAS the CkPS, but it was replaced with an aftermarket that didn't work correctly,, or at all. Since it was replaced with new, that couldn't be the problem, right? So you go trying other things.

It is critical that sensors be OEM. Either Mopar branded or NTK/NGK. Even quality names like Bosch and Echlin should be avoided.

 

This is some very good advice. it is not difficult to test the crank sensor with a simple multi meter and don't cost anything. I purchased a cheap crank sensor for a dakota a few years ago, it lasted 2 days and it crapped out.

 

Can you get the engine to fire and keep it running with the throttle? A scanner with live data will help diagnose this issue. I dont think the 96 had a sentry system but I've been wrong before.

 

NOOOOOOOO!!!!!!!!!!! IT CAN'T BE!!!!!!

 

Did it? Skim in 96? Ritzy

 

There has already been a lot of time spent on this Jeep for the issue.. If you can take the time to try and detail as best as you can for everything having already been done to it, so far as all of the parts having been replaced and with what, detailed history of the symptoms, any other data you feel may be pertinent, etc...

I think you can find the reasons and get this fixed if you take a systematic approach. The previous mechanics attempts may have worsened the whole ordeal rather than have helped?

I think going back to the basics is your very first step. The battery.. how is the battery? A good battery, battery cables and terminals, and the connections here at the battery are of paramount importance. These must all be proper!

The next thing that comes to mind is the grounds. These are also one of the most important things needing to be totally proper. If the grounds are not proper, all sorts of strange and unusually difficult to diagnose symptoms may occur. You may never be able to find the problem if bad grounds are contributing to the reasons. They must all be undone and cleaned up really well using abrasive techniques because you cannot see to tell if they are actually okay. I would clean every single ground in the engine compartment and also the hidden grounds located behind the different panels throughout the Jeep. It is probably going to be necessary to do your own research if you want to be able and try to get to all of them. If you do not have a Factory Service Manual (FSM)? The FSM can easily be found online to download the manual specific for your Jeep.

I would also want to disconnect and clean all of the rest of every single electrical connection/connector located throughout the entire Jeep as well too.

An off the hip shot - I think it could possibly be the fuel pump has gone south and is showing symptoms of being faulty. A fuel pump does not ussually go bad suddenly to totally stop working completely, and it can present as faulty with different symptoms of varying degrees in level of severity. A fuel pump should never drop the supply of fuel or pressure when the vehicle is turned on and running. If it were showing signs of failure.. sometimes the vehicle will stop operating to stall out and die exactly as how you explained is happening to your Jeep. I would want to know what is happening with the fuel pressure. Fuel pressure can test normal for psi at any time and then drop out... I would hook up a fuel pressure tester gauge to the fuel rail and watch it to see what it does. When the Jeep dies there should still be the same normal fuel pressure being maintained at the rail if this were not the reason.

 

FSM for '96 is hard to obtain

for engine electrical, use a '97 FSM

No (factory) immobiliser on '96 (check if an aftermarket system has been installed)

when you say it stalls, does it still stall if foot is kept on throttle ?