94 5.2 ZJ lost spark
#1
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Year: 1994
Model: Grand Cherokee (ZJ)
Engine: 5.2 Magnum
94 5.2 ZJ lost spark
So I've been stumped on this for a week now. I was driving and it completely shut off, simultaneously the check engine light came on (wasn't on beforehand). Up until that point it ran perfectly fine, no misfire, no stumbling, no hard starts. I was able to verify on the side of the road that I had lost fuel AND spark.
First thing I did was replace the ECM, that fixed the fuel issue, though I still wound up putting a new pump in just so it was done. I've also checked all my relays and fuses and they all seem to be good. I've verified that I have power and pulse going to the coil, I don't appear to have spark beyond the coil. I've gone through 2 different coils, and replaced the magnetic pickup under the distributor cap (the biggest pain in the *** so far). I know the crank position sensor is a possibility, but given how difficult they are to do I hesitate to go straight to that, I've also seen on multiple other forums that for people with my issue, the crank sensor didn't fix the issue. Anyone have any ideas on something I missed?
First thing I did was replace the ECM, that fixed the fuel issue, though I still wound up putting a new pump in just so it was done. I've also checked all my relays and fuses and they all seem to be good. I've verified that I have power and pulse going to the coil, I don't appear to have spark beyond the coil. I've gone through 2 different coils, and replaced the magnetic pickup under the distributor cap (the biggest pain in the *** so far). I know the crank position sensor is a possibility, but given how difficult they are to do I hesitate to go straight to that, I've also seen on multiple other forums that for people with my issue, the crank sensor didn't fix the issue. Anyone have any ideas on something I missed?
#2
CF Veteran
So...no diagnostics? Just replaced the ECM just like that? I think you put yourself into a crap-shoot. Sorry if that seems harsh. Run diagnostics and get any codes now, FWIW, if possible.
#3
Senior Member
Welcome to the forum.
If the coil has the correct solid connection (not yet confirmed) and the correct pulsed connection (confirmed), has already been swapped (confirmed) then the ground connection must also be solid (not yet confirmed). When I swapped my coil I scraped off some paint under the ground wire connection.
If the coil has the correct solid connection (not yet confirmed) and the correct pulsed connection (confirmed), has already been swapped (confirmed) then the ground connection must also be solid (not yet confirmed). When I swapped my coil I scraped off some paint under the ground wire connection.
#4
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Year: 1994
Model: Grand Cherokee (ZJ)
Engine: 5.2 Magnum
I actually did the sequence to find codes and it wouldn't flash. The light just stayed on, the fuel pump also didn't kick on even though the fuse was fine. I finally got it running on Saturday. Turns out the rotor shattered into pieces. Still not sure how it happened because I checked the rotor a few days before and it wasn't broken.
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Year: 1994
Model: Grand Cherokee (ZJ)
Engine: 5.2 Magnum
I wound up figuring out the coil was good the hard way (absolutely shocked the f*ck out of myself lol), so I pulled the cap again and the rotor and the rotor was hashed. It broke and I'm still not sure how, but I replace both that and the cap, and it fired up. I checked the rotor after it quit running and it wasn't broken so I'm not entirely sure how that happened but it's running great now.
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