Starting cirucit failure question
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Starting cirucit failure question
I've got an 86 f150 302 with that's getting a key on/engine off code 87. The truck hasn't run in 3 months and I'm trying to figure it out. (BTW I have a new fuel pump relay and a new high pressure fuel pump so I know they're not the culprits.)
I'm going through the Haynes manual fuel pump troubleshooting and I got the part where it says ground the fuel pump terminal to hotwire the fuel pump to listen for it running. I can hear the fuel pump relay switching on and off and can also hear a click somewhere in the engine itself but not sure what's clicking and the fuel pump never turns on.
Also, in the electrical schematic I can see that there's an EEC relay but I don't see one anywhere in the truck. From what I can tell, the fuel pump relay is supposed to have a green connector and the EEC should be brown, but again, I can't seem to find it.
I'm going through the Haynes manual fuel pump troubleshooting and I got the part where it says ground the fuel pump terminal to hotwire the fuel pump to listen for it running. I can hear the fuel pump relay switching on and off and can also hear a click somewhere in the engine itself but not sure what's clicking and the fuel pump never turns on.
Also, in the electrical schematic I can see that there's an EEC relay but I don't see one anywhere in the truck. From what I can tell, the fuel pump relay is supposed to have a green connector and the EEC should be brown, but again, I can't seem to find it.
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The EEC relay is behind/underneath the dash gauge cluster attached to the EEC IV computer 'box' on the right-hand side of it.
Do you hear the fuel pump run for a couple of seconds when you turn the key to the 'on' position? That would tell you essentially that the circuit is intact. If I recall correctly, the fuel pump relay receives voltage for a few seconds from the computer when it is turned to the on position, directly from the starter circuit while cranking, but thereafter to actually run-in the 'run' position the computer needs to see a signal from the IDM (pin #4, same as coil negative) to keep the fuel pump relay energized. So...a bad TFI module or distributor pick-up assembly could also shut down the fuel system.
Of course then there's the possibility of a popped inertial safety switch.
Then, it could also be like my '85 5.0 EFI, which I am quite sure at this point is haunted. I also met some guy today that looked an awful lot like William Shatner that claimed he saw a gremlin under my truck pulling random wires and reconnecting them in strange places. He was almost hysterical. Either explanation is plausible with the luck I've had with it...
Do you hear the fuel pump run for a couple of seconds when you turn the key to the 'on' position? That would tell you essentially that the circuit is intact. If I recall correctly, the fuel pump relay receives voltage for a few seconds from the computer when it is turned to the on position, directly from the starter circuit while cranking, but thereafter to actually run-in the 'run' position the computer needs to see a signal from the IDM (pin #4, same as coil negative) to keep the fuel pump relay energized. So...a bad TFI module or distributor pick-up assembly could also shut down the fuel system.
Of course then there's the possibility of a popped inertial safety switch.
Then, it could also be like my '85 5.0 EFI, which I am quite sure at this point is haunted. I also met some guy today that looked an awful lot like William Shatner that claimed he saw a gremlin under my truck pulling random wires and reconnecting them in strange places. He was almost hysterical. Either explanation is plausible with the luck I've had with it...
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Thanks I'll go out and test the EEC relay today and update how it goes.
Early in the process I had hoped that it was my inertia switch but remembered the connector is just sitting there and there's no switch attached to it so that's not it.
Tempest, I think your gremlin might have come to visit me in Florida during the winter. Run out and fix your truck before he comes back!
Early in the process I had hoped that it was my inertia switch but remembered the connector is just sitting there and there's no switch attached to it so that's not it.
Tempest, I think your gremlin might have come to visit me in Florida during the winter. Run out and fix your truck before he comes back!
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If you are looking at the correct connector, the fact that the inertia switch isn't there very much *is* a problem! The switch connects the wires together to form a circuit to power the pump; without said switch, the wires can never be connected together, the pump will never have power to it....
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If you are looking at the correct connector, the fact that the inertia switch isn't there very much *is* a problem! The switch connects the wires together to form a circuit to power the pump; without said switch, the wires can never be connected together, the pump will never have power to it....
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