Fuel Pump Manual Over Ride ? Help

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jagonza
Posts: 121
Joined: Mon Feb 01, 2016 12:03 pm
Your car is a: 1977 Fiat 124

Fuel Pump Manual Over Ride ? Help

Postby jagonza » Thu Sep 22, 2016 8:08 pm

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,
1977 Fiat 124 - Frankenstein engine
1999 VW Cabrio - Stock
1988 Fiero GT
And a couple of Daily Drivers

frischling
Posts: 5
Joined: Sat Nov 21, 2015 1:48 am
Your car is a: Fiat 124 spider CS

Re: Fuel Pump Manual Over Ride ? Help

Postby frischling » Mon Sep 26, 2016 2:10 am

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
Posts: 366
Joined: Thu Sep 11, 2014 10:28 pm
Your car is a: 1979 Spider 2000

Re: Fuel Pump Manual Over Ride ? Help

Postby kmoses » Mon Sep 26, 2016 8:50 am

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 ... tch-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
Posts: 121
Joined: Mon Feb 01, 2016 12:03 pm
Your car is a: 1977 Fiat 124

Re: Fuel Pump Manual Over Ride ? Help

Postby jagonza » Wed Oct 05, 2016 5:49 pm

Kmoses, a thank you that's exactly what I needed to know
1977 Fiat 124 - Frankenstein engine
1999 VW Cabrio - Stock
1988 Fiero GT
And a couple of Daily Drivers

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Nanonevol
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Posts: 828
Joined: Thu Nov 13, 2014 9:17 am
Your car is a: 1977 Fiat 124 Spider
Location: Medway, Massachusetts

Re: Fuel Pump Manual Over Ride ? Help

Postby Nanonevol » Wed Oct 05, 2016 7:35 pm

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?
1977 Fiat Spider
1985 Jaguar XJ6
1967 Triumph Bonneville (hard-tail chopper)
1966 BSA Lightning

jagonza
Posts: 121
Joined: Mon Feb 01, 2016 12:03 pm
Your car is a: 1977 Fiat 124

Re: Fuel Pump Manual Over Ride ? Help

Postby jagonza » Fri Oct 07, 2016 9:01 am

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.
1977 Fiat 124 - Frankenstein engine
1999 VW Cabrio - Stock
1988 Fiero GT
And a couple of Daily Drivers

KGROLLE
Posts: 7
Joined: Mon Nov 06, 2017 8:55 pm
Your car is a: 1972 Fiat 124 Spider

Re: Fuel Pump Manual Over Ride ? Help

Postby KGROLLE » Fri Jan 19, 2018 11:29 pm

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
Posts: 1278
Joined: Sun Aug 24, 2008 9:20 am
Your car is a: 1978 Spider [1979 2 ltr engine]
Location: Aiken, SC

Re: Fuel Pump Manual Over Ride ? Help

Postby zachmac » Sat Jan 20, 2018 4:46 pm

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: viewtopic.php?f=6&t=35468&p=273025&hilit=FORD+INERTIA#p273025
Jeff Klein, Aiken, SC
1980 FI Spider, Veridian with Tan (sold about a year ago), in the market for another project
1989 Spider, sold
2008 Mercedes SL65
2008 S600 Mercedes V12

KGROLLE
Posts: 7
Joined: Mon Nov 06, 2017 8:55 pm
Your car is a: 1972 Fiat 124 Spider

Re: Fuel Pump Manual Over Ride ? Help

Postby KGROLLE » Sat Jan 20, 2018 9:33 pm

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!


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