Hello,
heres the problem, I have a 1978 pickup, and a little while ago everything was good. Then, my battery cable came loose and wouldnt let the truck run. Electrics were intermitent, replaced the cable but now the charging light is on and the fuel pump relay isn't getting power. It will close, and I took the case off and it is working properly, but the power supply is cold. It is a white and black wire. I can't find a wiring diagram for the 78 that actually shows an electric fuel pump so I have no idea where it goes. Any ideas? Thanks!

 

W-B,white with black stripe are ground wires, B-W, black with white stripe are power ( hot).

 

Yeah, the black with white stripe isn't getting any power.

sorry for my miswording above.

 

Check all your fuses,if good ,disconnect the wires where connected & check each run for continuity to ground, would be a short, except the W-B wire!!!

 

Ok thanks will do!

 

The fuses were all pretty nasty, so i just replaced them all, and found the black and white wire to be good, (no short to ground.)
The question is: "why would the battery cable being having a bad connection mess with the fuel pump?" The fuel pump quit right when that happened and didnt come back on, so the battery thing must have been the catalyst. What else can I check? Thanks

 

If the key was on ,could have poped the IGN fuse, it is the one that triggers the pump relay!

 

That sounds like a likely culprit. However the fuel pump relay does operate. But if it cuts off the main fuel pump power, that could definitely be it. Any idea where the ignition fuse is? The fuse box doesn't show it to be on there.

 

Drivers kick panel !

 

If you mean the fuse box near the drivers left leg I just replaced all the fuses. But I did find something which may be of interest, with just the ignition on, I get no voltage, but with the starter running I get 9 volts. Helpful?

man, this sucks, with a complete wiring diagram this would be so much easier, but I just have no idea of how that fuel pump gets power.

 

Fuel pump done, but now truck wont run.

Well, it is not the route I wanted to take, but I just routed new power to the fuel pump relay so that is done. But I dont have the tank installed yet, so i hooked up a temp fuel tank which just gravity feeds fuel straight into the fuel filter, and now the truck starts perfect for a about 20sec and dies immediately. It will start back up but then dies as before. Then it won't start, if I spray a bit of starting fluid it starts right up but dies. It happened the exact time as when the battery cable loosened. Seems like a electrical problem tied to the carb. Not sure how or why though.