1996 Jeep Cherokee Sport 4.0L Crank No Start

Hi, I have a 1996 Jeep Cherokee Sport 4.0L. When I turn the key over it will crank but I'm not getting any spark to the engine. I checked the voltage to the coil and only get .007V. I traced the wire heading back to the ECU and back probed the plug and get 4.6V. I then tested continuity on the positive wire going from the ECU to the coil and got 55ohms, on the ground/negative side I got .5ohms.

I don't have communication with the ECU, but I didn't have communication with the ECU even when the car was running. I'm assuming I should get 12V coming from the ECU to the coil, but I don't know. Any advice or help would be appreciated.

Hey PSHACK! I snipped this part of the OE wiring diagram for reference:



All voltage testing at the coil needs to be done with the engine cranking, as the ASD relay won't be energized otherwise. With a test light connected to B-, the dark green/orange wire should light brightly. Test light connected to battery positive, the black/grey wire should pulse quickly. These tests can be done with the coil plugged in or unplugged.

Report back with what you've found and we can test further.

Hey, Tyler! I hooked up a test light to B-, to the dark green/orange wire and cranked the engine and it did not light up at all. I then hooked the test light to B+, to the black/grey wire and the light pulsed quickly.

PSHACK wrote:

Hey, Tyler! I hooked up a test light to B-, to the dark green/orange wire and cranked the engine and it did not light up at all. I then hooked the test light to B+, to the black/grey wire and the light pulsed quickly.

Good! The pulsing on the black/grey means the PCM is trying to fire the coil. That suggests the PCM is alive and getting CKP input.

The missing power on the dark green/orange gives us good direction. Your next stop is fuse #20 in the Power Distribution Center (underhood fuse box). Your test light connected to B- should light on both sides of the fuse. Key on, key off, cranking, doesn't matter.



If fuse #20 is good, we'll need to dig into the ASD relay itself. If fuse #20 is popped, slap another one in there and see if it pops immediately. :silly: If it doesn't, see if the engine will start.

I finally got a chance to test fuse #20 and it was popped I threw a new one in there and it started right up. Drove it all today and haven't had it pop again. Do you think I should look into why it popped or do you think it was just a fluke? Threw me off when I checked it with an ohm meter. Helps to pull the fuse out so as not to get a false ready. I appreciate your help and time. Thank you, Tyler!

Awesome! Glad to hear it's up and running again.

I would definitely spend at least some time digging into why the fuse blew. It's not likely to be a fluke, IMO, and it might leave you stranded if it pops again.

ScannerDanner actually made a video series on this issue about 10 years ago. :silly: Definitely check it out for ideas on where to go with your short circuit testing: