Fuel Pump Manual Over Ride ? Help

[jagonza]

I have an electric fuel pump on my 1977 ( the wiring matches a 1976 though)

I want to prime the fuel lines prior to starting the engine. When i put the ignition switch to the first position the fuel pump does not get power because the fuel pump relay does not close until it sees that there is some oil pressure. Once you start to crank the engine it generates oil pressure the oil pressure switch( "18/4" in the wiring diagram) closes, the fuel pump then starts to pump and i get fire.

My question is can i run a switch to the relay to fool the fuel pump into thinking there is oil pressure and thus prime the fuel system prior to starting. I would use a push button as i realize the oil pressure switch acts like a safety in case of an accident.

Anyone tell me please how to rig that up at the relay - which terminal needs what _ ground or 12 v ??

I don't want to just run power to the pump itself.

thanks,

[frischling]

Why would you do that ?

If you have problems with your start check all the other tings ( ignition,timing,...)

The pressure from the pump is very fast in the lines. That is not the Problem.

And yes. Let it as it is. Ist for your own safety.

[kmoses]

Easy enough to do. You will need a toggle switch that is 3 lug 2-Position ON - (ON) Momentary.
Cut the power wire going to the fuel pump and connect it to the normally on contacts with the center lug going to the fuel pump. Then connect a fused 12+ to the remaining lug. When you activate the toggle switch power will go to the fuel pump, when it is released, the normal power path to the fuel pump is restored. Granger has this switch on sale: https://www.grainger.com/product/NKK-To ... itch-2TPD9# and it is rated at 20 amps @ 30 VDC and a cost of $3.

Remember, if you don't feel comfortable doing this stop and hire someone who does!

[jagonza]

Kmoses, a thank you that's exactly what I needed to know

[Nanonevol]

That's great but, as frishling noted however, it seems you have another problem(s). I don't think your car should need the fuel pump to be pumping while cranking to start. Shouldn't it start on what is already in the carb float bowl?

[jagonza]

as far as what is in the float bowl, i live in atlanta, it gets well over 110F in my south facing garage and the car is not used except on very nice weather weekends, it may go a month without a start (longer ion the winter) , so yes i do need to refill the bowl sometimes, not a big deal i just dotn want to stress the starter with the extra 10-20 seconds of cranking just to get fuel up.

[KGROLLE]

I'm interested knowing what wiring diagram you are referring to when you mention "18/4". I have been advised to install an oil pressure safety switch to cut off the electronic fuel pump if the oil pressure fails. I am looking for a metric oil pressure safety switch (any leads on this appreciated!) and then need to know how to install/wire it.

[zachmac]

The system is not wired per factory per what you describe. Or you just don't realize that the fuel pump IS running while you crank before the oil pressure builds. The factory wiring has power to the pump when cranking regardless of oil pressure, Once you release the crank position back to running the circuit only stays powered IF oil pressure has built up. This is a safety feature designed to kill the pump if you get in a wreck and the engine stops (no oil pressure) just inn case the crash severed the fuel line (pump still running would pump gas out the break).

You can try disconnecting the starter and holding the key to run to see if the pump is running or have a friend assist as otherwise it is hard tyo hear the pump running while cranking. As was stated above, if it is running when you crank and you are not starting quickly the problem may be elsewhere.

BTW, I rewired mine to just run whenever the key is on as have several people BUT I also wired in a relay and a Ford inertia switch into the circuit. That way if I crash it still cuts off the pump. Very easy to get a switch cheap and just mount it in the trunk.

Take a look at this post: http://www.fiatspider.com/f15/viewtopic ... IA#p273025

[KGROLLE]

Thanks for the input but you mention "factory wiring". My electric pump is aftermarket, made by Facet. It replaced the original mechanical pump. I don't think my '72 had any wiring to anticipate the shutoff of the fuel pump (mechanical). The new electronic pump was also installed up front rather than in the rear trunk. I'll fix that when I reinstall the new engine and everything I pulled out of the engine bay. As part of this project, I'm rewiring with a Painless Harness and upgrading wherever possible, i.e. incorporating this safety shutoff and the Ford inertia switch you recommend. I certainly appreciate your input, thanks again!