engine randomly quits while driving and then wont start for 20 minutes... then repeat

[maxaud]

'90 XJ
I have a problem... I will be driving the Jeep and it will randomly shut the engine off, I will still have power and everything but the engine just stops and I'll try and start it but it just keeps turning over without starting.... then if you wait like 20 minutes it will restart again and do the same thing over again...

My guess is that the ECU doesn't always have power for some reason...

It's not throwing any codes.

[J-Roc]

push the pedal to the floor (hold it WTO) and try and start it, post your results. Sounds similar to my IAC problem I had a this past week...
How does it drive otherwise? Any other symptoms?

[maxaud]

push the pedal to the floor (hold it WTO) and try and start it, post your results.

WOT instead of WTO? I tried that, nothing. I don't think its getting spark.

[Matthew Currie]

Consider some component failing when it gets hot. A prime suspect if you have no spark is the crank position sensor. If you have an ohmmeter you coult try reading its resistance at the connector when it is cold and then when it fails.

Sorry, no manuals handy here as I'm traveling, but you should be able to find the pinouts somewhere. The resistance should be somewhere in the 125-200 ohm range as I recall.

[maxaud]

there are times where I can drive it all day and it wont give me the problem...

someone said it might be an ignition control module... could this be a suspect?

where is the crank position sensor located at and what does it look like?
thanks.

[Runnin'OnEmpty]

It's down on the bellhousing driver's side. The connector is on the driver's side near the firewall, just follow the wiring to the sensor. There's many posts on the CPS here, and those are classic symptoms for a CPS failure.....

[maxaud]

thanks, I'll check it out... I'm leaning towards ICM/Coil..

this was taken from a website talking about them.. seems to describe my symptoms..

SYMPTOMS OF A BAD IGNITION COIL
Although modern ignition coils are very reliable, they can exhibit failure symptoms that are common to all coil configurations. A cranking, no-spark condition or a severe engine backfire might, for example, characterize a coil failure. The vehicle also may exhibit a temperature or humidity-related starting or stalling complaint.

[maxaud]

but then again... taken from another site...

Crank Position Sensor Strategies: If a crank position sensor fails, the engine will die. The engine may, however, still crank but it will not start. Most problems can be traced to faults in the sensor wiring harness. A disruption of the sensor supply voltage (Hall effect types), ground or return circuits can cause a loss of the all-important timing signal.

[Wildride15204]

cps!!!!!!!!1

[DonkRado]

Yeah. Sounds like the CPS to me. Take a look at this the next time it happens. As soon as you feel it cutting out, look at your tach and see if it just flies down to zero even though the engine is obviously still rotating. Mine would also stall and come back to life at times. When it did that, it would fly down to zero, then just bounce back up to RPM as if nothing had happened.
It's a really simple replacement, but shop around for the replacement CPS. It's been several years, but I think I recall Advance had it for like ~$100 and Autozone had it for around $40.

The easiest way to explain it I think is that the CPS flakes out, which tells the computer that the engine is off, the computer then cuts out all of the 'ignition on' devices... including the engine.

[maxaud]

either the engine is on running great or the engine just shuts off, no in between stuff, It doesn't sputter, it doesn't hesitate... just like shutting off the Jeep but without turning the key.

It makes back fire every once in a while... not often though. and the Jeep has a glass pack so that might be the cause of that..

thanks for the help guys.