Bronco Forum - Full Size Ford Bronco Forum banner

Fuel pump primes backwards wiring issue?

1269 Views 11 Replies 4 Participants Last post by  Rob_64-365
Hello all, i have a problem i cant seem to get fixed. I have an 87 Bronco with a 302 C6 transmission. Ill start by saying there has been several hands over the years on this truck and not all did things the right way IMO. A lot of the plugs and or connectors have been replace/repaired. When i try to start the truck (key in the run position) i can hear relays clicking but no fuel pump. When I turn the key to the off position the pumps prime as they should if the key was in the on position. Another thing is the self test plug isnt working anymore. When i plug code reader into it, it wont start to run diagnostics. I have replaced the ECC, distributor, ignition switch, starter, starter solenoid,fuel pump relay and the EEC relay. The plug on the ignition switch crumbled in my hand when I unplugged it so I am not 100% sure they are in the right place. Also the plugs for the relays were replaced and im not so sure that they are rewired right. In moving with the wires around on the deivers side fender well the fuel pumps quit coming on at all but started working again after a little more wiggling but still ran backwards. I feel like there is just a wire out of place or possibly broken somewhere. ANY help is GREATLY appreciated Im not sure how much more i can take on the truck geez
1 - 1 of 12 Posts
Hello all, i have a problem i cant seem to get fixed. I have an 87 Bronco with a 302 C6 transmission. Ill start by saying there has been several hands over the years on this truck and not all did things the right way IMO. A lot of the plugs and or connectors have been replace/repaired. When i try to start the truck (key in the run position) i can hear relays clicking but no fuel pump. When I turn the key to the off position the pumps prime as they should if the key was in the on position. Another thing is the self test plug isnt working anymore. When i plug code reader into it, it wont start to run diagnostics. I have replaced the ECC, distributor, ignition switch, starter, starter solenoid,fuel pump relay and the EEC relay. The plug on the ignition switch crumbled in my hand when I unplugged it so I am not 100% sure they are in the right place. Also the plugs for the relays were replaced and im not so sure that they are rewired right. In moving with the wires around on the deivers side fender well the fuel pumps quit coming on at all but started working again after a little more wiggling but still ran backwards. I feel like there is just a wire out of place or possibly broken somewhere. ANY help is GREATLY appreciated Im not sure how much more i can take on the truck geez
I had an 89 with a similar issue, only it was operator error. I replaced the fuel pump (I LOVE that the fuel pump was on the rail on that thing as opposed to the tank), but I wired it backwards so it de-primed when the key was turned. Anyway, I swapped the wires on the pump and like magic everything worked fine.

In general this sounds like a wire chasing project. Best of luck.
1 - 1 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top