myraus

On My 91, ever since I got it a couple of months ago, it would take an abnormally amount of cranking to start. And when it was running it was idling pretty rough, at least to when I compare it to how my previous 4.0's ran. I haven't driven it much since then, but what I've done is replace the fuel filter (old one was a lot heavier than the new one), cap and rotor, and got rid of the heater valve which was replaced with hoses right from engine to heater core.

I noticed that when I replaced the cap and rotor the idle smoothed out quite a bit till yesterday. I took it for a short drive, shut it off for about 15 minutes to do some errands, then went to start it back up and it would crank but wouldn't start. Also, when it was cranking I would step on the throttle and move it to different positions that it would catch a bit but still not start. It did start after some more cranking but it feels like it shouldn't be this difficult to start it all the time.

Any ideas where to look and test? I was thinking CPS may be faulty or dirty (saw one post on here to where the AX15 versions may get clutch dust on the CPS and it affecting it's ability to pick up a good signal), or coil, fuel pressure, etc.

I would really like to get this fixed before I go on my road trip on Saturday. I hope someone can help out. Thanks.

RTorrez1

Next time it doesn't want to start you need to see what you are missing, fuel or spark. You should have a strong blue spark. Any other color will cause problems with hard to start and rough idle. Your 91 should have 39psi +or- 5psi at the fuel rail. The fuel pressure will need to be tested with a mechanical pressure gauge attached to the fuel rail. This will give you a place to start looking. Hope it helps.

myraus

Thanks for the advice, RTorrez1. I went and bought a fuel pressure tester and found out what the problem was. It is the fuel pump! What's happening is when you turn the key to energize the pump, no pressure would build. Only when you started cranking would it buildup enough psi then it would run. And running psi is only 30, so it isn't even coming close to spec. Lastly, when I shut off the engine the built up pressure wouldn't stay in the lines. In a few seconds it was all bled off.

So my XJ is gonna stay home till I come back from my holidays, then the pump and my 3.73 axles will be going in after!