'73 Fuel pump: its cut, where should it go?

[BadDog]

At some point in ancient history, the wire from my fuel pump was cut. The mechanical one seems to work just fine with no starvation or vapor lock issues, but our club's tech guru thinks I should either hook it back up or bypass it because the mechanical pump has to pull fuel through the non-working electric pump.

I found the fuse for the fuel pump, and it looks fine but I can't figure out where the wire from the fuel pump was hooked into the electrical system. Both ends of fuse lead back into bundled wiring and (apparently) back over the the P/S footwell junction blcok/connectors/relays. The long wire from the fuel pump up to the front of the car comes up the P/S firewall, then over the hood latch area, across the top of the firewall and ends up in the area of the windshield washer bottle/pump, where it just stops, looking like it was cut. I tried rooting around the interior to see what it might have been connected to, but I've found nothing. Any ideas?

-Ken P.

[Ed]

Your electric fuel pump is back by the fuel tank, passenger side. You can bypass it with a longer section of hose to feed directly from the tank to the line.

Additionally, the wiring for the fuel pump doesn't go anywhere near the washer bottle. The only wires over there are for the washer bottle and the brake system.

[Ed]

There is a "piggyback" connector between the engine bay wiring harness and the voltage regulator. From there it goes to two relay's over on the passenger side footwell. There is a long section of wires with a fuse labeled "fuel pump" that goes over towards the fuse block. I'm not sure where it connects into the wiring harness that goes to the rear of the car. At the rear of the car by the passenger side tail light the wires go through the floor. One set of wires go to the fuel level sending unit on the tank and the other to the electric pump.

Try a voltmeter on the wires to the pump and see if your getting power.

Hope that helps.

[BadDog]

Thanks Ed. I'll have to take a second look at the electric pump: the other wires just looked like ground wires to me, I figured the long one (going underneath the car along the driveline tunnel and then up the firewall over the D/S and then cut) was the positive power lead. Now I'm wondering what that wire's for

I guess I could just bypass the electric pump... isn't there a fuel filter in there though? Is the filter in the engine bay "good enough"?

-Ken P.

[280z]

speaking of fuel pumps, does anyone know the correct hose that should be used to connect the fuel tank to the fuel pump. after i replaced the fuel pump on my car, i had a hard time starting the motor. i think this was because the fuel pump hose was bent in a way that wouldnt allow the gas to pass, just like a garden hose when its twisted. the hose is very soft and easy to clamp when replacing the pump. is it meant to be like that or was the original hose one of those thick "L" shaped hoses or something?

[dogma420]

it should just be standard 5/16" fuel line....if it looks 'kinked' just jimmy rig it by adding extra hose and looping it.

There is 'sort of' a fuel filter in the pump...the fuel filter in the front will work just fine however.

[kenz240z]

I would guess that the wire on your car isn't original. Every car I've worked on has had a wiring harness that ran inside the car from the front to the rear that provided the connections to the tail lamps, back up lamps, rear license plate light, fuel tank sending unit, etc... This harness is tied into the under dash wiring (main harness) by way of a large, multi-pin connector. I would remove the mystery wire, especially if it is not connected to anything on either end.

If the electric fuel pump isn't hooked up then bypass it. If you keep it in line (working, or not) then be sure to open it up and check the fuel filter inside. Mine was clogged up with sediment from the tank. The previous owner had parked the car and left it sitting for 7 years before I bought it. Caused a bit of a fuel starvation problem in my Z, but I finally figured it out!

[beandip]

Thanks Ed. I'll have to take a second look at the electric pump: the other wires just looked like ground wires to me, I figured the long one (going underneath the car along the driveline tunnel and then up the firewall over the D/S and then cut) was the positive power lead. Now I'm wondering what that wire's for

I guess I could just bypass the electric pump... isn't there a fuel filter in there though? Is the filter in the engine bay "good enough"?

-Ken P.

Any wire that runs from the pump under the car forward is not stock and is a add on. The factory fuel pump power wire is green and there is a black which is ground. As Ed has stated it is with the sending units wireing and extends to the rear and up inside the cabin on the passinger side close to the tail light where they plug into the wire loom. And yes there is supposed to be a inline fuel filter between the tank and the electric pump. I am running only the electric pump and both filters. Gary

[ncz]

Dog, before dis-assembly mine was running on the mechanical pump only and ran fine. No vapor lock. My local Z guru did this to most Z's in the area. Thats the path of least resistance, IMO

[BadDog]

Thanks guys, that's all good info... I think I need to a) take a 2nd look at that dead-end wire. There's 3 wires coming out of the fuel pump, I think that was the top-most of the 3 and decide if its worth bothering with. The car doesn't starve for gas ever, and no vapor-lock issues (knock on wood). I think my mechanical pump may be wearing out though because I think its the source of a loud whir-ticking noise that changes with engine speed (in-gear or in neutral, clutch in or out) and I've checked and double-checked my valves and header.

-Ken P.

[=Enigma=]

There's 3 wires coming out of the fuel pump, I think that was the top-most of the 3

If I recall correctly from memory, the pump on my 73' has only two wires. One for power and one for ground. I don't see a reason for a 3rd. Must be for something else an not related but don't take my newbie word for it.

[mlc240z]

maybe it was wired to some type of kill switch in case of an accident to cut power so you didn't flambe`. sounds like it could have been routed towards the coil.

good idea, by the way. see if there's a mystery piece of electrical hardware on the driver's side around the cut wire.

bart