SHawanijeep

I changed most of the sensors and completely changed the fuel pump with its filters, but the car at first is going normally until the engine heats up at a normal temperature. It is not a great height. The car starts to snail and sneeze, and sometimes the engine stops . Sometimes the engine stops working and the strange thing is that today when I stopped I decided to remove the air from a room of Fuel injection sprayers found them empty, which means that the reason the fuel does not come continuously, so what is the reason? Can the computer stop the pump from working? the car GRAND CHEROKEE MODEL 89 ZJ

Noah911

Hello,

I do believe the answer is yes. The PCM does ultimately have control over the functions of fueling. As such, it is definitely possible the PCM could be one of the reasons for having an issue with the fueling.

Have you taken a fuel pressure gauge attaching it to the fuel rail to get an accurate reading of the Jeeps fuel psi to see what it is? It would be a good thing to do for in this type of a situation you have described. I would want to leave the fuel psi gauge attached in order to be able and obtain readings of what the psi actually is under varying running conditions.. at idle, with key just turned off to see what the psi level holds as, during slow cruise and low RPMs, while the Jeep is under a heavy load going uphill, and during periods of high RPMs.

I think this would be where I would start with it. Checking out the fuel psi readings under varrying running conditions and different engine loads. And to see if the fuel psi goes down or not when the engine is stalling itself out.

I think I would also want to pull all of the spark plugs in order to get a read on their conditions. I would mainly be looking at them all to see if the spark plugs may be pointing to the direction as having a very lean engine running condition. And to see if any of the spark plugs look substantially different from any of the other spark plugs comparing them all with one another.

(edited to add):
Also, if the fueling is getting cutoff. I would also want to check and see if the sparks are being cutoff at the same time as with the fuel. Checking to see if there are sparks being produced whenever it stalls again...

SHawanijeep

Thank you for the response. I would like to clarify that the fuel system then changed only two days ago and with the start of everything everything is excellent. The engine runs smoothly and if you start the car before it reaches the necessary heat, it starts well and the accelerator pedal works in harmony and just to move a distance of 2 or 3 km it starts When I step on the accelerator repeatedly and quickly, sometimes the car continues normally and sometimes intermittently until the engine stops

Noah911

In all honesty, I believe I would do as complete of a tune-up to the Jeep as what I deemed necessary to begin with as my very first step if it were me. It sounds like the fuel pump and the fuel filter have already been taken care of at this point. I believe most of the late 1980s all of the way up through the early 2000s model years of Jeeps could probably all use a new fuel filter in most cases. I think of doing a fuel filter replacement as being another one of the normal routine general maintenance items which should always be taken care of on a regular basis (about every 20,000 miles). It is kind of a shame how a lot of these Jeeps have their fuel filters set up in such a way as to be a rather difficult and time consuming project with how their fuel filters are located all of the way up and inside of the gas tank. The WJs have their fuel filters in an easy to access place so as to only be a five or ten minute process, which is nice.

I do not know a whole lot in regards to the earlier 1980s model years of Jeeps. I know they have some nuances and differences specific to them for sure though. For instance, I believe the testing procedure of the earlier model years 1980s Jeep Crank Position Sensors (CkPS) are little different than the model years of Jeep I am most familiar with, maybe? I think a common way of testing the CkPS on the earlier model year of Jeeps is done in part by reading the resistance? I would have to find out from one of the trusted sources I go to, and look up the specific procedure of it in order to be absolutely certain about it. I know with how you are describing the symptoms as how they are specifically happening on your Jeep, the CkPS would be one of the suspects very high up on my list of possibilities that I would have going on in my head. I would fully scrutinize and do a complete testing of the CkPS as soon as I had the opportunity to do so.. as I believe the CkPS would be a rather highly likely item to possibly cause the same type of similar symptoms as what is happening on your Jeep in the way you are describing those symptoms. The CkPS does have a solid history of causing Jeep Cherokee's and Grand Cherokee's to stall out when they are up and at normal-hot engine running temperature. The increase of temperature in the engine compartment of a normal-hot running engine results in the CkPS to produce abnormal signals. This is due to the heated sensor having unusual resistance in relation to the elevated temperature. When the sensor cools off some, or when the Jeep is started with a cold engine, the CkPS returns to acting normal how it should be and produces normal signals again when it is cooled down like that. This is a classical sign of having a failing CkPS. Only a genuine Mopar branded sensor should be used for a replacement CkPS in these Jeeps. You could try testing the CkPS when the engine is cold, and then test it again after the Jeep stalls itself out (when the sensor has been heated). Compare these two test results to one another, and to what the specifications should normally be based from an official source.

Another more likely possibility of something which could cause the same similar type of symptoms as having a failing CkPS, and elevated temperature related stalling and crank/no starts when warm like what you have described, would be when you have a failing ignition coil. A failing ignition coil may work completely normal when it is cool, and then when it is warmed up in a normal-hot engine running compartment the resistance of the ignition coil may begin to turn abnormal. This may also be something to cause the Jeep to stall itself out in the same similar way as having a failing CkPS does, until it begins to cool down a little. You could check the resistance of the ignition coil when the engine and the ignition coil are both cold.. and compare this reading you get when everything is cold to another reading you get after the Jeep has stalled when both the engine and ignition coil have been heated. Compare both of these readings to one another, and to the normal specifications of what the ignition coil should be from an officially sourced manual.

Checking for wether or not there are any sparks happening immediately after when the Jeep stalls would be a very top priority of mine. It really sounds like to me that your issue may be something related to the ignition. I would definitely want to check and see if there were sparks normally happening or not immediately after the Jeep stalls, and whenever it will not start. Checking for the sparks and wether or not there is proper fueling are really the very first things needing to be verified whenever there is a crank-no start condition, in my opinion. The sparks should be snapping blue (not yellow or red). I would also want to listen closely for having the fuel pump prime how it normally should whenever I turned the key during episodes when it was refusing to start as the first step for verifying the fueling, and then check for fuel pressure at the rail.

I would complete as much of a full tune-up as was possible to get done. New spark plugs correctly gapped and new spark plug wires at the very least. Old worn out failing spark plugs and their wires are some of the other things which are known to cause the same similar type of symptoms.. which may also present as heat related symptoms in their nature too. If these things were in any way needing to be done anyway, I would get them replaced right away in order to have a good base to work off from as a start. I would also do a full battery voltage test. Other things I would do is clean up every single ground located throughout the engine compartment, the battery cable terminals, and all of the other main electrical connections I could see.. in order to set myself up with a good base to work off from during the diagnostics.

SHawanijeep

I would like to thank you especially, Mr. Noah, for your wonderful effort that you are making to help me, and I really feel that you are beginning to approach the solution to my problem ...
I will do all the necessary tests and verification required and I will tell you the results Thank you again