wiring fuel pump shutdown switch

[chpr1972]

I have a 66 Lemans and I am installing EFI. The shutdown switch is a Ford switch and a aftermarket wiring harness.The switch has 3 terminals,NO, C, NC. The NC terminal has a smaller wire and is white with a red stripe. The C terminal has a blue wire and is a size larger. The NO terminal has a yellow/white wire and is the same size as the blue wire. What is the correct way to wire the switch. The EFI is a Holly HP EFI with TPI and dual 4BBL throttle bodies on a tunnelram. The fuel pump is a Tanks Inc. in tank pump. I thought that I put this post on earlier today with my phone but can't find it. DUMMY ME, you can't teach an old dog to use a smart phone!!

[andrewb70]

I have a 66 Lemans and I am installing EFI. The shutdown switch is a Ford switch and a aftermarket wiring harness.The switch has 3 terminals,NO, C, NC. The NC terminal has a smaller wire and is white with a red stripe. The C terminal has a blue wire and is a size larger. The NO terminal has a yellow/white wire and is the same size as the blue wire. What is the correct way to wire the switch. The EFI is a Holly HP EFI with TPI and dual 4BBL throttle bodies on a tunnelram. The fuel pump is a Tanks Inc. in tank pump. I thought that I put this post on earlier today with my phone but can't find it. DUMMY ME, you can't teach an old dog to use a smart phone!!

Whats the purpose of this Ford switch? The Holley HP will shut the fuel pump down if the engine is not running.

Andrew

[chpr1972]

It's in case of a wreck or rollover, it shuts the fuel pump down. I was told to wire one in for safety

[andrewb70]

http://www.studebaker-info.org/tech/fpsafetysw.html

Seems simple enough. I would put it after the fuel pump relay and before the pump.

Andrew

[chpr1972]

Thanks! The third wire had me confused as some instructions had it as the 3 second, pump on, when starting. Just dummy me trying to make something simple, hard. As it works as a breaker it should not matter which way it is wired. Thanks for the web site as I would have wired it flat , not vertical.

[H2Ogbodies]

Why not just use a simple 2-prong GM oil pressure switch? I would run your fuel pump trigger wire for the pump relay through it-this way, if the engine dies or if oil pressure drops below 5 psi it will kill the pump. I understand the principle of the Ford inertia switch design but there are other ways to skin a cat as it were.

[Kenova]

Every Vega built had an oil/fuel pump safety switch. It is by-passed so the pump will run when
you are cranking the engine over. Once the engine is running with oil pressure (hopefully) the
oil pump is powered through the switch. The switch turns on the idiot light and shuts the
fuel pump down when you loose oil pressure.

Ken

[andrewb70]

Why are we talking about shutting the fuel pump down if the oil pressure goes down? The Ford inertia switch is for shutting the pump off in case of collision.

Andrew

[Motorcitydak]

Why not just use a simple 2-prong GM oil pressure switch? I would run your fuel pump trigger wire for the pump relay through it-this way, if the engine dies or if oil pressure drops below 5 psi it will kill the pump. I understand the principle of the Ford inertia switch design but there are other ways to skin a cat as it were.

If you did this you would not have your fuel pump turn on until your engine had oil pressure.

What I would do is just a simple good quality switch that would interrupt the fuel relay signal from whatever you are using to control it. An engine computer usually controls that so just find that wire and get a switch on it. You would leave that switch in the on position at all times until you either want to turn the car on without the fuel pump coming on or, god forbid, you needed to in an accident

Might want to talk to Holley, ask if their computer would shut the engine down if you lose oil pressure. If it does you could also use another relay that the computer could control that would not leave you needed another switch for this application

[andrewb70]

If you did this you would not have your fuel pump turn on until your engine had oil pressure.

What I would do is just a simple good quality switch that would interrupt the fuel relay signal from whatever you are using to control it. An engine computer usually controls that so just find that wire and get a switch on it. You would leave that switch in the on position at all times until you either want to turn the car on without the fuel pump coming on or, god forbid, you needed to in an accident

What if you're unconscious, the engine is still running, and there is a leak in a fuel line? That's what the inertia switch is for.

Andrew

[rickpaw]

What if you're unconscious, the engine is still running, and there is a leak in a fuel line? That's what the inertia switch is for.

Andrew

Yep, the inertia switch is standard equipment in most Ford vehicles. I have one installed in mine. Back to OP question, iirc one of the wires is for a warning light that lit up when the switch is tripped. Don't remember which wire though.

[David Pozzi]

I have heard the Ford Inertia switches can trigger from a large bump or if someone smacks the fender with their hand on cars where the switch is in the trunk.
There is some talk about it here: http://www.ffcars.com/forums/68-road-racing-discussions/286040-fuel-pump-inertia-switch.html
https://www.youtube.com/watch?v=AIPhM2DA_xA

[Aficionado]

David Pozzi is correct--if you drive a police package Crown Vic, a little enthusiastic driving can shut it off. (I expect other models would have the same issue, but that's only one I've had that experience with.)

[chpr1972]

These switches can't be that bad.As far as I know they are used on the high performance Mustangs. If you have an accident it can take a couple of minutes for the motor to shut down to loose oil psi but the Ford switch shuts it down instantly. If a fuel line got torn off a lot of gas could be pumped out with a pump rated to 1000 HP at 42.5 lbs psi. Thanks for the imput

[Motorcitydak]

I hit a curb too hard at a track day in my lotus and it shut off my fuel, had to get towed off. Figured out the problem and reset the switch. They are a good idea but not my favorite thing