Hey all,
OK I've read about every thread on this problem and my mind is spinning off into the void... so... here's what happened and what I've done hoping to get some insight from the greater XJ Cherokee World-Mind.

I've got a '96 Cherokee XJ 4.0

So... on a very hot July 4th I was parked watching fireworks in my neighborhood with the A/C on when the car kind of just died... no sputter or shaking, just off. So I turned the key and the starter cranks and cranks but no start.
Here's what I've done to diagnose so far:

1. Plugged in my OBDII reader with key on and NO COMM (it was working just the day before). I tried the key-off-key-on trick to get any codes, but my CEL isn't lighting up at all. Maybe dead bulb?
2. Checked all fuses I can see and switched around the ASD, Fuel Pump and Starter relays... all seem to be OK.
3. Unscrewed and wire brushed all the ground screws I could find in the engine compartment.
4. Unplugged and replugged the CPS (I read that might do something but no go)
5. Checked spark at distributor and ignition coil... no spark that I can see when cranking starter.
6. Jumped fuel pump relay and I can't hear anything, but I'm parked on a busy street so I'm not sure if I can hear anything. Tried smacking the gas tank with a rubber mallet to see if the pump was dead. Still no pressure.
7. Rented a fuel pressure tester and plugged into the schrader(?) valve. Cranked engine and no pressure.
8. Tomorrow I'm going to check voltages from the CPS just to see if that's the problem before I start throwing parts at the thing.

That's about all I've done. I'd appreciate any comments on what else I can try.

Thanks!

Mike

 

Hey all, OP here. Just wanted to give you all an update
Turns out it was the crankshaft position sensor. Final diagnostic data was when I unplugged the CPS, the CEL light came on on the dash (it didnt light up when turning key to ignition like it should with CPS plugged in) and fuel pump worked (actual pressure at the schrader valve). Plugged the CPS back in and both things failed again.
Had a bit of a time finding the right CPS since rockauto and other sites had wrong part listed. Guess '96 was a transition year and some things changed.
I want to thank everyone who responded with helpful ideas. This is a great community!
Cheers,
Mike

 

Oh, the fun of a dead CPS. Common symptoms are an inexplicable "cranks but won't start" and a fuel indicator reading empty. Happened to me one night in a parking lot and I thought someone had drilled my tank and drained all the fuel out. Nope. CPS.

Did you get a Jeep OEM CPS? The non-OEM ones seem to have a rather notorious failure rate. Good luck!

 

Yep got OEM CPS but thinking about getting a cheap one just to keep on hand in case this happen again

 

When mine went in my '00 it would just stall when it reached operating temperature. Start right back up. Maybe stall again. Maybe get to where I was going.
And when I say stall just like you shut off the key. In the following week it got worse on the starting right back up part.
No CEL or Pending CEL's, no weird gauge crap, etc. Even doing the test it came up good.
But I attribute mine to thermal failure so it might explain the lack of other things associated with a bad CPS and why it tested OK.


Hey just buy another Mopar one. That is what I did. Now I have one in "stock". LOL.
Mine was bought more out of fear of Mopar ones becoming NLA.
And if that happens imagine what I can charge for it 10 years from now if I never use it. MLOL.

 

That's pretty weird. How did you end up diagnosing it? Throw parts at the problem??

 

I was leaning towards the CPS but.....
Posted here for starters.
One guy said his buddy had the exact same problems, verbatim was the word he used, in his '00 and it was the CPS.
Most others agreed.
Got a few check fuel pressure posts but the Jeep did not sputter and die. Just shut off like you turned the key off.
So kinda did not think it was that.
Like I said did the CPS test but reading about thermal failure and getting a good reading when cold kinda made sense so.....
So figured what the hell. At the time Jeep had about 155K on her and figured if nothing else I get a new CPS out of the deal.
Turned out that was the problem

 

Interesting, thanks for the explanation! Sounds kind of like a latent failure after heat soak.

Thermal failure can be a helluva drug!