79 LBZ Fuel Pump Wiring.

[Jim Fierst]

Having a problem with the electric fuel pump wiring circuitry . It worked when Ii drove it into the garage to do a head gasket change. I discoinnected the pump wires to do other things and when reconnected it would not work.No current to the pump. I have checked out the line from the relay box to the pump and it is good. Both the relays supporting the start cycle and run cycle check out as well. I kow there is some involvement with the oil pressure to shut off the fuel in case the oil pressure drops when running. When putting some grounds on the instrument lights I damaged the oil pressure light and gauge connectors
so if the signal has to go through them to any relay that could be part of the problem.The pump used to start operating as soon as the key was turned on and run while starting. I removed the oil pressure gauge sender and installed a mechanical gauge so I really don't need it or the light.
I have a 1979 sedan wiring diagramsmanual which is very complete along with the owners manual schematic which I have been using to try to find the problem.
Two questions .. Are there or were there any detailed application specific schematics available that would only show something like the fuel pump circuitry .
Assuming I cannot find the problem what woulf be the best way to wire around the problem. I was thinking of powering the pump with a relay triggered by some key on sourca ,fused of course.

[Jim Fierst]

An additional piece of information.. When I turn the key on the oil pressure light does not come on. When I disconnected the wire to the 'sending unit it does?? Seems backwards to me..that could be the result of the damaged connector..

[Will]

Jim;

Can't make out the root of your problem from your description but can offer the following:

a) The wiring diagrams book (about 20 ppg) is the most detailed wiring schematic I know of.

b) The dual-relays and OP switch setup is an overly complicated turd of an engineering solution. Ditch that mess and simply use a Holley oil pressure safety switch- all you need to do is adapt the 1/8" NPT male switch sensor to your oil system. It is a SPDT switch that provides power when cranking, then keeps supplying power to the pump as long as the engine is running. Which is what the complicated stock system does, except the Holley switch does it with one $20 part and about two relays and 15 wires less complexity.

Number of parts is inversely proportional to reliability IMHO.

-Will

[Jim Fierst]

Problem resolved. I was reading the relay lay out sheet as if viewed from the rear of the car instead of the front. When I found that out i checked the start and run relays and the start was bad. I replaced and it pumps fine. It seems that the relay must have failed just a few days before I started the head gasket replacement. There was enough fuel in the float bowl to start the car so the lack of a starter relay was not a problem.