My XJ has an attitude..

Alright here's the deal. I have an '88 xj 4.0. Every 2 or 3 days or so, when she gets warmed up, she doesnt like to start back up if i shut her off. I have replaced the fuel pump, fuel fiter, did a complete tune up. She just keeps cranking over, and if i wait about half an hour she will start. Could anyone shoot me some advice?? Thanks

Try this to diagnose if it is a CPS problem. CLICKY

Hi,
Most likely culprit would be the CPS (Crankshaft position sensor), this happened on my 93 XJ, it would just cut out a few miles from home and would not restart for 15-20 minutes. I had a new CPS fitted and it's been running fine for a couple of years now. The CPS is fitted to the top of the Bell housing and I think what happens is that the housing expands as the engine warms up, this moves the CPS away from the flywheel, which is where the CPS is getting it's timing from and so the engine quits. After it all cools back down it will restart and run until the next time it quits. I think the CPS must get weaker with time for some reason and a new one can handle the expansion but an old one cannot. Hope this helps.

Yep CPS if you disconnect the CPS and check it w/ an ohm meter it should read 200 Ohms +/- 75 Ohms. Over time they kinda demagnatize them selves. Also if its kinda running rough just visually check the wire for burned/melted insualtion. I had one ground out one time that was interesting. good luck

Hi again,
I forgot to mention that the lead from the CPS needs to be zip tied to the firewall to keep it well away from the exhaust pipe, you don't want it melting through in the middle of nowhere!!

Just brainstorming here......the biggest clue to me is that you mention that it won't start AFTER you turn the engine off.

A possibility for that symptom would be the camshaft position sensor (located in the distributor). Normally if the crank sensor experiences thermal failure, (due to heat) it stops providing that reference signal to the computer and the engine dies no matter where you are at.

If the camshaft position signal is lost while the engine is running (again; a thermal type of failure; heat related) the computer will calculate spark timing based on the last cam sensor signal the engine will continue to run. However, the engine will NOT run after it is shut off. They can be tested easily; get yourself a manual and a meter. Would be worth your time......

If the engine dies at unpredictable times WHILE running, then I agree that the crankshaft position sensor may be suspect. Good Luck!

Jeepcreep said:

the lead from the CPS needs to be zip tied to the firewall to keep it well away from the exhaust pipe, you don't want it melting through in the middle of nowhere!!

Click to expand...

x2!

Thanks guys I apreciate it, I'll get to checking both CPS's tomorrow morning!