I bought a non running (yeah, bad idea) 1991 xj cherokee laredo a couple of weeks back and im down to nothing trying to get it to run.

So far i have checked and/or replaced:

DTCs with key trick- 12, 33 (or whatever number a bad idle air motor is its bad and i know it, cleaned it worked for a day-going to buy a new one), 55

Compression- meets 75% rule and test was done with throttle open

Fuel pressure- 31psi with koeo and holds steady while cranking

Injectors- tested with a noid light,pulse looks normal.

ASD relay- clicks on with ignition on, clicks off when you let off the start position. fuel pump turns on for 2 seconds every time the key is turned.

I know the CKP is new and do not see a reason to test it again ( i ohmed it out and tested for reference voltage already) however since i have injector pulse i assume it to be good. (is this correct for a 91?)

Replaced cam sensor, actually entire distributor in a hasty move i regret. I did this because i saw the unreliable spark.

Replaced the ignition coil 4 times.

Replaced the plugs,plug wires, cap and rotor.

Replaced ecm 3 times.

Replaced the factory ground from the firewall to the cylinder head and the factory ground from the block to the battery with 0 guage HPM stinger flexible car amplifier wire...should have good ground. but you never know.

I have replaced the fuel lines and filter, figured it needed it anyway im sure.

SPARK-THIS SEEMS TO BE KEY, I GET SPARK TO RANDOM CYLINDERS AND IT DOES NOT SEEM VERY STRONG TO ME. DEFINATELY NOT A BLUE SPARK MOST OF THE TIME. AND ONLY 4 TO 5 CYLINDERS WILL SPARK AT A TIME.
(I FIRST TESTED STRAIGHT OFF THE COIL, THEN GOING IN A CIRCLE,WITH THE COIL WIRE ATTACHED TO THE CENTER OF THE DIZZY CAP, TESTED EACH POST ON DISTRIBUTOR WITH THE SAME SPARK PLUG WIRE AND SPARK PLUG. IT SEEMS TO NOT LIKE 3 AT ALL AND SOMETIMES NOT 6. MAKES NO SENSE TO ME.

CHECKED VOLTAGE AT THE COIL, GET BATTERY VOLTAGE ON POSITIVE SIDE OF COIL HOWEVER IT DUMPS TO ZERO AS SOON AS YOU HIT THE KEY (NOT SURE IF THIS IS NORMAL-WOULD SOMEWHAT MAKE SENSE IF IT WAS NORMAL SEEING AS THE POWER IS BUILT AND RELEASED IN AN IGNITION COIL) DO NOT SEEM TO HAVE PULSE ON THE COIL WHEN I HOLD A TEST LIGHT TO THE OTHER WIRE ITS JUST A STEADY LIGHT WHILE CRANKING. The one time i did get a pulse for a few seconds it acted as if it may start then ofcourse stopped.THIS PART SEEMS VERY KEY.

sorry about all those caps, just wanted to get your attention to that part. and sorry about the long drawn out story just wanted to show most of what i have done.

Im running out of ideas and im chasing my tail here, i can on occasion get a slight "acts as if it may start" out of it, and it seems to coincide with when the voltage to the ignition coil pulsed once or twice....its time for some outside insight/advice if you guys dont mind please. Its most definately an electrical gremlin but i am not exactly an auto electrician.

 

update: Just used my noid lights for something besides injectors, used them to check for pulse at the coil. Odd, i SORT OF have a pulse. hard to explain but its like its more like a real humans pulse, a long solid light followed by two flashes then a long solid light again.

Forgot to mention this because at the time i felt it unimportant, but when i removed the transmission inspection cover (yes i went this far lol) i noticed that someone had gotten red spray paint on 1/3rd to 1/2 of the windows of the flywheel reluctor ring and what appears to be a light scratch, almost a white mar 2/3rds of the way around that ring. in other words i wonder if it is possible that the 2 are connected?

Surely spray paint couldnt fool the crank sensor could it?

 

A new crank sensor does not mean it's a good crank sensor. Even new puppies die sometimes.

 

Could be, but i dont think one would see a pulse signal to the coil or injectors if the crank sensor was unable to do its job. However, with this particular basket case i am contemplating buying another crank sensor just because i know 99 percent of the time it IS the problem.

 

I went thru 3 crank sensors be fore I went oem.