I have a 93 G. Cherokee with a 4.0 with starting problems. I have to turn the ignition switch to the on position for about 90 seconds before I hear a relay energize in the power distribution box and the jeep will start. It will keep starting as long as I don't let it sit to long. But when I go to start it the next day the problem starts all over again. Once it starts it runs fine. If the fuel pump is losing pressure it should'nt take 90 seconds to build up pressure. Has anyone experienced this problem before. Thanks
and bummer i have seen this very same problem before to the T. And I diagnosed it to be the PCM. And guess what.............................................. ........ It was. Put a PCM on there and like magic it fixed it. Man you just dont know what a good technician and a fluke meter can figure out. Thats why I get payed as much as I do.Cause I eat, sleep, and breath and s__t jeeps from 8-6 mon-fri all year long....
I am in the process of finding out why Grand 2002 4.0 does the same thing. So far this is what my mechanic and I found. Fuel pressure at fuel rail 52# during idle. When engine shuts off, fuel pressure supposed to hold pressure for around 10 min (i think) My pressure drops to 0 in approx 10 sec. Bubbles in the fuel rail when purged. (due to heat boiling the fuel at low pressure in line) Could have injector leaking or fuel tank check valve leaking. I am hoping for the check valve problem. I am changing my filter/regulator tomorrow and adding an inline fuel check valve to try first. If that don't work, I will just change all injectors with new ones. Bosch set around $180 i think. GM service bulletins have a known problem with the check valve in the tank. And dealer does not sell just the valve. Write up says you need to change the tank. This is a recall on some models. Will try and go that route if this be the problem. And that is my two cents.
I have a '93 ZJ with the I6. I've since done some more searching and FAQ reading and pretty sure it is the PCM, as mentioned here. It's been three months and it isn't getting any better. Does it eventually just not work anymore and you get stranded?
I have a little extra cash now so I am going to dig under the hood today and see which ECM I have so I can order one from these rock auto dudes.
So @sastanley - you never followed up on if you were able to fix your 93 ZJ 4.0L I6. It sounds like a problem I've been having with my 93 GC. I am at the point where the PCM almost seems to be the only thing left and would appreciate it if you could let me know what you ultimately had to do to your 93? Here's a description of what I'm experiencing and what I have done:
I have replaced the spark plugs, plug wires, distributor cap and rotor, fuel pump, fuel filter, distributor (new, including camshaft position sensor), crankshaft position sensor and nothing makes any difference. It is practically impossible to start. So, I am going back to the basic troubleshooting, even though I did these things before when I began having problems with it. One guy told me to check the engine temperature sensor and wiring as it could cause the stalling, super long crank times, spitting and backfiring, dieseling, popping and spitting back and quickly losing all engine power at highway speeds when pressing the accelerator pedal aggressively as well as in town speeds or stopped. It is much more difficult to keep running at in speeds or stopped than at highway speeds.
Was your ZJ having the same issues my 93 ZJ is? Thanks a bunch!
Mine would not start until the check engine light went off. I had to keep the ignition on for about 10 minutes before it would fire. After doing the surgery on the PCM, it fires off as soon as i hit the key. My capacitors did not physically look bad but it was defiantly the issue. If you know how to solder and have basic mechanical skills, you can get this done in a about an hour. I think it cost me a total of less than $5.00. Here is the link if you want to buy them. http://www.ebay.com/itm/5pcs-220uF-3...item418b3863fa