I am currently chasing the same problem with my 91 4.0L. I was driving it home and it just died on me. After trying to start it for a while, with it backfiring with full throttle, I broke the distributor tab off and popped the distributor out. After replacing the distributor with a new one, I have no signal at the injector plug, but I still have spark.

I am banking on the sync signal from the distributor being good, since it is a new distributor. I would like to test the sync signal generator in the distributor but it requires an analog voltmeter(which I don't have). My factory manual says that "the sync signal works in conjunction with the engine speed sensor[CPS] to provide the engine controller with inputs to establish and maintain correct injector firing order." So I have a new CPS on the from the parts store to see if that fixes the problem. If it doesn't, I guess I will be buying an analog voltmeter to test the new distributor.

I hope this helps, I will let you know what happens with it tomorrow.

 

Ok keep me posted, the only thing I would say about you changing the CPS, if your check engine light is not on, then it is most likely good, if the CPS is bad it would through a trouble code.

On my cherokee I am at a lost, I checked the voltage at the fuel injector connectors, with the ignition on and it has 1.2 volts, so somewhere I am not getting voltage to the injectors.

 

you say you have no injector pulse if you squirted fluid in the motor and it ran its a fuel issue

 

fuel problem

 

Thanks RICH, I believe I have isolated the problem.


Its not a fuel problem, I have 40lbs of presure on the rail, and today I took voltage readings at the fuel injector connectors, and I had anywhere from 1.2 to 2.5 volts, and after moving the harness it would jump to 7.5 volts so i am thinking the 12v feed from the computer is shorting out, so tomarow I will dig into the harness.

 

at least your getting somewhere with it thats kool

 

Well after uncovering the britle electrical tape and finding the fuel injector wires, I noticed where it makes a 90 degree turn to the firewall the insulation and wires had be broken, where the splice was (6 wires into one) is where the 90 turn to the firewall was. It was stillin the factory splice heat shrink.

when I found the main Power Fuel injetor wire I put a meter on it, It read 7.5v with the ignition on, I was still concerned that I did not have 12 volts, not sure I am supposed to? So I re spliced the wires (temporarily) hooked up all the sensors, and connected the noid light and cranked it, the noid light flashed while cranking, so I hooked everythng up, and the Jeep fired up and runs perfectly.


Thanks to everyone that gave the tips to solve this issue, this by far was the most frustrating for me.

Rob

 

Sweet that you got it running. You are supposed to have a lower amount, like 7 volts, at the injectors.

Did you ever have your transmission or transfer case worked on. Because it is easy to damage that part of the harness when the motor is tilted down to get the bell housing bolts on a tranny replacement. Just a thought.

I got my jeep running as well. It was throwing codes for the CPS and the sync signal generator. Not sure how that happened. The distributor was new too!!! I took it back to the parts store and they took it back. So I got a new housing(mine broke originally) and a new sync signal generator from the parts store and I gave them back a bad housing and bad generator. I got all my money back too. Nice to deal with young dumb****s at parts stores.

 

I just bought the cherokee a week ago, the broken xfer case in the back with another complete NP231 D, waiting to go in, I bought this Jeep for $500.00 engine works now, and xfercase is in, I will pick up a slip yoke tomarow, and I should be in business.

I don't think im going to worry about the .5 volts

Glad you got your running too

 

kool you got it run ning

 

I have 99 wj and it has a misfire on cylinder 4 and I found out that the injector runs for about 20 seconds and stops any help would be great

 

 

Where was the main power wire located?

 

Each injector wire is splice into each other, from what i can remember, at the 90 degree turn up by the firewall is were the main wire is, hope this helps