1992 Cherokee Sport, 4.0L 6cyl

XJ Sport cranks and cranks but won't start. After about 25 minutes and a jumpstart later, the CHECK ENGINE LIGHT and the MAINT LIGHT come on and flicker when I crank it, then a few turns later, it turns over.

Now, this ONLY happens in the morning when its a little chilly. Once I get it running I have NO problems. Can run around all day...shut off, starts right up..I go to work at 8am and leave at 7pm ... starts rght up. Go home, start it up one more time at 10pm or so..no problem. Get up in the morning...crank, crank, crank. Nothing.

WHAT I DID:
Changed the battery, plugs, rotor, cap, wires, FUEL PUMP RELAY, ASD RELAY, Coolant Sensor, Oxygen Sensor

WHY I HAVE DOUBTS THAT ITS THE FUEL PUMP:
If it was an issue with the pump itself I would have problems while it was running (right?), but like I said, once it runs it's fine.

Any ideas?

 

CPS- or another sensor is my guess.

 

Sounds like the dampness/dew is getting to the high voltage parts...
plug wires
dist cap
coil

in that order.

Try running it at night, your 10pm start, and look for sparks.

 

Replace the crank sensor.

 

UPDATE ON THE ISSUE: Finally got this resolved.

It was the computer... swapped it out, Jeep starts right up every time!

Hope this helps someone in the future!

Take care,

James

 

before you replaced it, did you try to reset it?

 

Yes, I did try to reset it...made no difference. Popped a different computer in now it turns over with no effort.

 

mine does that in the cold days we have in fl when ever it drops below 50 next time it dont start try tapping the map sensor with a wrench tap not beat when i do this mine starts every time its at the back of valve cover on fire wall