Jens Kleen

Hi guys, I have a 94 xj which has been running fine without missing a beat until tonight. today after driving for about 30min I went through a round about and the engine just stopped, with the "check engine" light on.
tried to clear the ecu, but no luck. I tried getting a fault code read out, but that's not possible through the dash board light because the "check engine" light is constantly on. What could cause that, crankshaft positioning sensor?
all spark plugs, injectors, distributor cap and rotor, spark plug cables, fuel pressure regulator and fuel filter have done about 5000.

freegdr

Did you try key on key off method to read codes ?

freegdr

Like this....


http://jeep-xj.info/HowtoECUcodes.htm

Jens Kleen

yeah, tried it few times, tried clearing ecu by disconnecting battery and touching positive to ground, reconnected battery, but no luck, the check engine light comes on straight away as soon as the ignition is turned on and won't turn off. tried the on-off-on-off-on procedure to see if it would give me a code (usually it does) anyhow, but the light just stays on without flashing or anything.

madmanmarty

Check for spark,then fuel.
Try starting in neutral first for Nss issues.

Jeep Driver

CPS or coil would be my guess.


"whilst", haven't seen that word in a while........:P

freegdr

Rent or buy scanner. Throwing parts at it will cost more in the end. And scanner can be used in future.

freegdr

Try this.......

Jens Kleen

thanks for all the suggestions,
just updating the current issue.
found the 30A engine control fuse blow, replaced it and can actually get code read out. it's 12 and 55 which is "battery disconnected within last 50 key cycles" which I did. Now it is not turning over at all, checked and cleaned the nss, checked and cleaned the cps, on the cps I got on about 1.7Mohms at first, but then went to open circuit when I retested it.
the start relay does not get any power to the common of the contact, only 12V on the coil when trying to start. Bridging 12V to the switched contact of the starter relay will turn over the engine, but not start it, guess there will be the spark missing because of the fault that is still holding up the ecu?

madmanmarty

Are u getting spark at a spark plug when u crank the engine?

Jens Kleen

just an update on the matter, I found the engine control fuse blown which is the 30A, I sourced another one and she started up no problem at all. I cleaned the nss and checked the csp just in case anyway. now I'm not sure why the fuse has blown, the xj has been running for a week without a problem and still going. as per wiring diagram it seems to be going to the fuel pump relay and through to the fuel tank system. other splices are going to the oxy sensor, transmission control module and the power train control module. I haven't found any wiring damaged around the fuel pump connection, but I'm not too sure what exactly has happened there. usually a fuel pump fault would be more consistent right?