Electric Fuel Pump ?

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Feb 24, 2008
Kennesaw, GA
I recently purchased new fuel pump for weber conversion. Can I get someone's advise on best way to wire. Can I hook it to existing oil sending unit or should it be seperate? Any advise would be greatly appreciated?
Why would you hook up electrical fuel pump wiring to an oil pressure sending unit?

Pump should be connected to some 12V hot source that is only hot when the key is on (i.e. ignition 12 volts). Pump should be mounted as close to tank as possible for two reasons:
(a) Electric pumps care pushers, not suckers.
(b) Vapor lock occurs between tank and pump. The shorter distance between tank and pump means the less chances of getting a vapor lock.
Use a relay...and use the + side of one of the wires off the coil... you can check with a mutimeter or test light. This wire is only "hot" when the ign is on. Use this wire as the trigger wire to turn the relay on...which would power your pump. Don't run a direct wire from the coil wire to your fuel pump. You would have 12 volts feedign the relay and 12 volts coming out of the relay to the pump. Ign on would trigger the relay allowing power to the pump. Ign off would cut the power at the relay thus turning the pump off.

Three wires. one wire feeds 12 volts to the relay (hot all the time), 2nd wire runs from relay to fuel pump (only powered when relay is energized) 3rd wire is your trigger...runs from ign on source (in my example above the coil + side) to the relay. So key on / ign on.... coil wire hot...fuel pump on, then key off, coil wire cold... fuel pump off.

You could choose other wires to use where only on with key on or ign on. All you need is a test light to figure out which ones are hot with ign on.

Most car parts stores would be able to provide you with a simple relay and most likely show you the trigger terminal, and then the continious hot terminal and the controlled or terminal that actually feeds the power to the device in question (fuel pump).
My guess is that the idea of hooking it to the sender is to have it shut off if there is no oil pressure?

If so, that is a good idea, but I would suggest a dedicated pressure switch for the job. Leave the stock bits to do just their job.
If you can find one, the GM Vega's used a switch just for this purpose as they only ever had an electric fuel pump. These switches have 3 terminals. A switched (ignition) or battery hot, pump supply, and start-mode by-pass. The latter is so that the pump will run without there being any oil pressure so long as the starter is cranking.

I have used this switch on two different vehicles. I normally come from the battery, through a fuse or breaker, and to the switch; then on to the pump. Oil pressure does not last very long in the engine after you turn it off (maybe 20 seconds max), and by going straight to the battery for power that is one less demand flowing through the ignition switch.

EDIT: This switch can be used to switch on and off a relay as well, but I ran a Holley Blue Pump, at the rear of a Suburban, for 5+ years (until the truck was rolled on the Grapevine) on just the switch.
Thanks guys for all the advise. With your help I feel much better about things. Happy Trails!

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