‘91 XJ Crank no start

[‘91XJ]

Hey all,

Got a 1991 XJ not too long ago. 4.0 4WD with 193k. One day it just died while I was driving it home from work and it has not started since. RPMs just dropped without any sort of noise to indicate something broke internally. It will crank and crank but nothing. Switched out the crank sensor with the echelon NAPA part and got out the multimeter to see if relays were properly working and here’s what I found:
- with the key turned to run the fuel pump primes
- in run, on the ASD relay cavity 30 has 12v and cavity 86 has 12v
- cavity 85 has 12v as well but I was thinking that needs to be a ground signal from PCM
-cavity 85 loses the 12v when fuel pump relay is unplugged

Does the ground signal from the PCM only happen when cranking?

 

[lawsoncl]

I think the PCM wants to see cranking before engaging the ASD relay. Does the fuel pump run again when you crank it? If not, I'd suspect the crank sensor or it's wiring. I also wouldn't rule out a bad new part. Injectors working or got spark?

 

[‘91XJ]

The fuel pump doesn’t run when I crank it. I didn’t know it’s was supposed to. I have intermittent fuel injector pulse and spark.

 

[lawsoncl]

The fuel pump will run briefly when the key is turned on, then stops until the engine computer sees cranking. No codes? It could be the distributor sensor too.

 

[‘91XJ]

It does prime for 2-3 seconds when I turn the key on. I also did replace the ignition pickup in the distributor. I don’t have any sort of scanner that will give codes for this year vehicle.

I am more confused why I would be seeing the 12v at three points on the relay unless that is normal. Everywhere I’ve looked says it’s should be like .2v from the cavity that gets the ground from the computer when the key is on.