302, Cranks but no fire from coil
07-02-2016, 08:58 PM
#21
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OK, so now I've installed a brand new distributor, and still the exact same problem
, no fire from the coil, and no crank signal from the Ignition Control Module to the coil.
Tomorrow I'm going to take back the new ICM and try a different one, as the troubleshooting steps from easyautodiagnostics.com still lead me right to that module.
Anybody have any ideas on anything I'm missing here?
, no fire from the coil, and no crank signal from the Ignition Control Module to the coil.Tomorrow I'm going to take back the new ICM and try a different one, as the troubleshooting steps from easyautodiagnostics.com still lead me right to that module.
Anybody have any ideas on anything I'm missing here?
07-02-2016, 09:01 PM
#22
Junior Member
Thread Starter
Little more progress.
Found that the 30A Maxi fuse that feeds both the fuel pump relay and the PCM is blown. A new fuse blew right away. Switched relays and still blew. Looks like I'm down to the PCM.
Found that the 30A Maxi fuse that feeds both the fuel pump relay and the PCM is blown. A new fuse blew right away. Switched relays and still blew. Looks like I'm down to the PCM.
07-02-2016, 10:25 PM
#23
Senior Member
What about a shorted fuel pump. On the scale of likelihood, I'd put that above the PCM.
Of course I could be completely full of it, but PCM's dont fail very often, and I can't ever recall seeing one fail in a way that would blow a 30A fuse. Just thinking out loud here.
Of course I could be completely full of it, but PCM's dont fail very often, and I can't ever recall seeing one fail in a way that would blow a 30A fuse. Just thinking out loud here.
07-03-2016, 08:17 AM
#24
Junior Member
Thread Starter
As far as I can tell, that fuse feeds the fuel pump relay, not the fuel pump, and when I switched out the relay with another one it made no difference. But that's still a good suggestion so as soon as I get back to the truck I'll pull the relay out completely and try it. If the fuse still blows, then the only thing left in that circuit is the PCM.
07-03-2016, 01:49 PM
#25
Senior Member
That fuse is the power supply to the pump, via the relay. Your diagnostic proceedure is right on, pulling the relay will definitely isolate the problem. At least you're in the home stretch now. Just remember the old saying about the light at the end of the tunnel. Pray that it's not the train! ...... Staying tuned.
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coachk64 (07-03-2016)
07-03-2016, 11:22 PM
#26
Junior Member
Thread Starter
Found it!!
There was a lot of great advice from this forum, and it led to some fantastic troubleshooting assistance.
After replacing the coil, Ignition Control Module, and the distributor, I was on the verge of replacing the Powertrain Control Module, but further checking (about 7 hours worth for two of us) finally led us to the problem.
After checking everything having to do with the ignition, we finally just disconnected everything in the entire wire harness. The plug that finally enabled us to turn the key on without an over-current condition led us to a wire bundle going to the transmission, so I crawled under the truck to check it out.
This wire bundle had come loose and was laying loosely against the transmission mount. There was a 1" gap in the plastic conduit, and that had rubbed against the mount until it had worn through the insulation on the wire that fed 12VDC to the transmission pressure module. When it welded itself to ground it blew the 30A Maxifuse that feeds the PCM and the fuel pump relay. We were able to trace it out on the wiring diagram to prove it, but it went through a lot of different connection points.
As soon as I separated it from ground, the truck started right up. A little tweaking of the new distributor and it is running better than ever.
Thanks again to all who contributed with their expertise and suggestions.
After replacing the coil, Ignition Control Module, and the distributor, I was on the verge of replacing the Powertrain Control Module, but further checking (about 7 hours worth for two of us) finally led us to the problem.
After checking everything having to do with the ignition, we finally just disconnected everything in the entire wire harness. The plug that finally enabled us to turn the key on without an over-current condition led us to a wire bundle going to the transmission, so I crawled under the truck to check it out.
This wire bundle had come loose and was laying loosely against the transmission mount. There was a 1" gap in the plastic conduit, and that had rubbed against the mount until it had worn through the insulation on the wire that fed 12VDC to the transmission pressure module. When it welded itself to ground it blew the 30A Maxifuse that feeds the PCM and the fuel pump relay. We were able to trace it out on the wiring diagram to prove it, but it went through a lot of different connection points.
As soon as I separated it from ground, the truck started right up. A little tweaking of the new distributor and it is running better than ever.
Thanks again to all who contributed with their expertise and suggestions.
07-03-2016, 11:53 PM
#27
Senior Member
Outstanding! I bet you're a happy man. Good job.
07-04-2016, 10:00 AM
#28
Senior Member
There was a lot of great advice from this forum, and it led to some fantastic troubleshooting assistance.
After replacing the coil, Ignition Control Module, and the distributor, I was on the verge of replacing the Powertrain Control Module, but further checking (about 7 hours worth for two of us) finally led us to the problem.
After checking everything having to do with the ignition, we finally just disconnected everything in the entire wire harness. The plug that finally enabled us to turn the key on without an over-current condition led us to a wire bundle going to the transmission, so I crawled under the truck to check it out.
This wire bundle had come loose and was laying loosely against the transmission mount. There was a 1" gap in the plastic conduit, and that had rubbed against the mount until it had worn through the insulation on the wire that fed 12VDC to the transmission pressure module. When it welded itself to ground it blew the 30A Maxifuse that feeds the PCM and the fuel pump relay. We were able to trace it out on the wiring diagram to prove it, but it went through a lot of different connection points.
As soon as I separated it from ground, the truck started right up. A little tweaking of the new distributor and it is running better than ever.
Thanks again to all who contributed with their expertise and suggestions.
After replacing the coil, Ignition Control Module, and the distributor, I was on the verge of replacing the Powertrain Control Module, but further checking (about 7 hours worth for two of us) finally led us to the problem.
After checking everything having to do with the ignition, we finally just disconnected everything in the entire wire harness. The plug that finally enabled us to turn the key on without an over-current condition led us to a wire bundle going to the transmission, so I crawled under the truck to check it out.
This wire bundle had come loose and was laying loosely against the transmission mount. There was a 1" gap in the plastic conduit, and that had rubbed against the mount until it had worn through the insulation on the wire that fed 12VDC to the transmission pressure module. When it welded itself to ground it blew the 30A Maxifuse that feeds the PCM and the fuel pump relay. We were able to trace it out on the wiring diagram to prove it, but it went through a lot of different connection points.
As soon as I separated it from ground, the truck started right up. A little tweaking of the new distributor and it is running better than ever.
Thanks again to all who contributed with their expertise and suggestions.