I bought a 1990 XJ this weekend for a little of nothing and I am trying to figure out what is up with it. If you turn it over it will just spin over and over. But if you hit it with one or two little puffs of starter fluid she fires right up and runs great but as soon as you shut it off and try again nothing until you hit it with the fluid again. I have replaced the fuel filter, cap, rotor and plug wires. Pulled the fuel rail and turned the key on and have a bunch of fuel there. Just need some ideas on where to go. Anything would be great.

 

Somebody has got to know something on this. I gotta get this thing going asap.

 

Injectors

 

I would check your intake and throttle body first, just to be sure.

 

Now that is weird. How about new plugs?

Also...I'd put a timing light on it just to see. Could be the computer telling the distributor to advance too far, too little, not at all. Worth a look if you have a light.

If it was a carb, I'd say the idle circuit was plugged. Is there such a thing with FI?

 

Stop,
He said it runs fine after getting it started, so the injectors are working.
The CPS is working, the CKS is working.

Starting fluid is doing the job required during Crank mode, not IDLE mode.
One of two problems I see.
1. Normally,the fuel pump primes the fuel rail for 3 seconds, test with fuel pressure gauge (NO OTHER METHOD please). Have someone listen in the gas tank with key ON, not cranking. Make sure the pump can be heard for 3 seconds.

If the pump runs but fuel pressure does not stay above 25PSI for several minutes (should be hours), you may need a new fuel pump. The electric fuel pumps have a built in check valve to maintain the pressure.

2. If the PCM no longer provides a signal to the fuel pump relay during cranking, the PCM is broke. Sometimes they fail in strange ways, I have one that fires up in CRANK mode then shuts off the injectors in IDLE mode.

I just checked my basement, I have a PCM on loan from a friend.
He might sell it if I ask nicely.

1989-1990
Jeep Cherokee (XJ) 4.0 L
Jeep Comanche (MJ) 4.0 L
6 Cyl. Engine, w/Automatic Transmission

Reference numbers:
S101140203A, S101140203-A, S-101140203-A, S101140203 A
EF8953005428, EF89-53005428, EF89 53005428
53005428, 53005-428, 53-005-428, 53005 428
53007842, 53007-842, 53-007-842, 53007 842

 

How fast is it cracking over the renix models take like 300 rpms to start things happening .

 

I would check the fuel system like the guy above said. I've seen this happen and it was the little check valve the only bad thing is that you have to take the tank and pump out to replace it but a cheap place to start the valve is not much and can be found at any auto parts. good luck these problems suck.

 

put a noid light or test light on one of the injectors and see if you have pulse during cranking. Sounds like keyon cranking signal is missing, i.e. bad wire, ignition switch or pcm.

 

Ok here's another quetion when you turn the key to acc the fuel pump should kick on and only run for a few seconds until pressured and then kick off right?

 

^^^^^^ I need help with my question above anybody got the info I'm looking for?

 

Enough WAGs (wild a$$ guesses) already people.

I'm not too sure about the renix system, but I think there is a ballist resistor for the fuel pump circuit. You may want to see if the fuel pump is getting any voltage to it while cranking.

 

not in accessory remember accessory is when u turn the key backwards, ur pump should kick on for a few secods the click before u hold it to start it and yes should shut off after 3 to 5 seconds

 

You should be able to hear it and you can almost hear in form in the jeep. or have some one stand back there and listen

 

That is correct.