OK, I was going to test fire my truck tonight. I got everything ready, primed the engine, pulled the fuel pump relays while I cranked it over and saw oil pressure on my gauge. Key off, relays back in. Now, when I turn the key on I get no fuel pressure. The pumps are not putting anything out. Here's a few things rmfreeze and I found when troubleshooting.
We pulled the pumps out to verify wiring that I hadn't forgotten to plug them in when I installed them, that was OK. But, when the key is turned on the pumps will only kind of click/hum for about 1/2 a second (sounds like they are "energizing"), then not do anything. We plugged a known good pump into the pickup harness and it does the same thing. When we checked the voltage at the main plug that plugs into the tank wiring, there is 6.8 volts on 2 different wires, those two wires are connected together inside some wire loom, and go into the tank as one wire which feeds the 2 pumps. If both pumps are disconnected, the voltage is 6.8 volts on the 2 plugs that actually plug into the pumps. If one pump is plugged in, the other plug has no voltage on it at all. It's almost like when a pump is plugged in it is grounding out or something. We tested one of the old pumps by jumpering it with 12V and it hums right along. The fuel level sending unit works fine. I can move it around and the gauge moves.
Can anyone tell me if there is supposed to be 12V supplied to the pumps? I guess I really need a wiring diagram to trace down the fuel pump wiring and find my problem. Another odd thing is that the grren "Cruise" light indication on the dash comes on when I turn the key OFF. Maybe it's related, maybe it's not.
We pulled the pumps out to verify wiring that I hadn't forgotten to plug them in when I installed them, that was OK. But, when the key is turned on the pumps will only kind of click/hum for about 1/2 a second (sounds like they are "energizing"), then not do anything. We plugged a known good pump into the pickup harness and it does the same thing. When we checked the voltage at the main plug that plugs into the tank wiring, there is 6.8 volts on 2 different wires, those two wires are connected together inside some wire loom, and go into the tank as one wire which feeds the 2 pumps. If both pumps are disconnected, the voltage is 6.8 volts on the 2 plugs that actually plug into the pumps. If one pump is plugged in, the other plug has no voltage on it at all. It's almost like when a pump is plugged in it is grounding out or something. We tested one of the old pumps by jumpering it with 12V and it hums right along. The fuel level sending unit works fine. I can move it around and the gauge moves.
Can anyone tell me if there is supposed to be 12V supplied to the pumps? I guess I really need a wiring diagram to trace down the fuel pump wiring and find my problem. Another odd thing is that the grren "Cruise" light indication on the dash comes on when I turn the key OFF. Maybe it's related, maybe it's not.
