I have a 1986 GMC Jimmy with a 2.8 in it and 114365 miles on it. It died one day and would not start afterwards. We found out it kept blowing the ecm-b fuse everytime you tried to start it. We have replaced the ECM, the ignition module under the distributor, the fuel pump relay switch, and the electronic ignition module, as well as the fuel filter with all new parts but it is still blowing the fuse. The truck tries to start but is not getting any fuel. I am not even sure what the ecm-b fuse runs so Im not sure what else to do. Any help would be appreciated.
How bout replace the STM with a RM. Try that and msg me for follow up. Good luck man
April, 2, 2007 AT 11:46 PM
Is the fuel pump running? You should be able to hear it run when you first turn the key to on. Listen with the gas cap off to be sure. Are you getting spark?
The ecm-b fuse provides power to the ecm, fuel pump relay, fuel pump, and the oil pressure switch. Test the pressure switch and check the wiring for shorts.
Good luck and let us know. : )
April, 3, 2007 AT 9:03 AM
It blows the fuse as soon as we turn on the key so I guess the answer would be no the fuel pump isn't running. We have replaced the fuel pump relay switch. How do I test the oil pressure switch? We have also replaced the ecm and I would assume it is getting spark because even with the fuse blown it tries to turn over it just won't fire.
April, 3, 2007 AT 10:01 AM
The oil pressure switch is the back up for the fuel pump relay when it goes. The PCM/ECM energizes the fuel pump relay-No power to ECM means nothing is gonna happen.
You need to track down the short involving the ECM-B circuit.
Disconnect all connectors at the ECM, replace the ECM-B fuse, now turn key to On-did the fuse blw?