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Old 02-29-2020, 03:56 PM   #1
JayChicago
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Default Fuel pump collision switch

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Originally Posted by JSeery View Post
You need the collision switch if you are using the elec fuel pump while moving.
Your opinions please, about collision switch. I am just now replacing the electric pump in a new-to-me 37 Streetrod. No mechanical pump. Going to add a low-oil-pressure cut-off switch. (a Holley part, open at 5 psi)

Do you think I should have a collision switch too? I guess it wouldn't hurt; belt and suspenders. But as I think about the risk being protected against, it would have to be a collision hard enough to rupture a fuel line, I'm unconscious so can't turn off the key, but still the engine keeps running a while on the gas in the carb. Whats the odds of all that? Maybe if I got rear-ended hard. Are there other scenarios, other risks I'm not thinking of? Are there other benefits to a collision switch?
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Old 02-29-2020, 05:48 PM   #2
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Default Re: Fuel pump collision switch

I weighed the possibilities of being in an accident where having a low oil pressure pump safety switch would be a benefit, against the possibility of that sensor or associated wiring leaving me beside the road wondering why the engine died. At my age, reliability won out over safety.

I have the oil pressure switch, which I will never install; PM me and I will send it to you.
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Old 02-29-2020, 06:50 PM   #3
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Default Re: Fuel pump collision switch

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I have the oil pressure switch, which I will never install; PM me and I will send it to you.
Thanks, that is generous of you. I appreciate that. But I already bought the switch and fittings, plan to install tomorrow. We're supposed to get one day of warm weather tomorrow, so I plan to spend it in my unheated garage. Can't wait for spring!
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Old 02-29-2020, 07:24 PM   #4
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Default Re: Fuel pump collision switch

There are a lot of scenarios - that don't involve a ruptured tank or line. Just think about if you happen to tip the car over on it's side - you're in a ditch. Gas starts to pour out of the carb, gets on the exhaust, fire starts. Meanwhile your fuel pump (depending on level in tank, where the pickup is, etc) - keeps pumping fuel at a furious rate to the carb. And - as the car is on it's side, the float assembly in the carb is probably not stopping the fuel from pouring in . . . and right out the top . . . making a HUGE fire. All the while, you're hanging from your seat belts!
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Old 02-29-2020, 07:35 PM   #5
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Default Re: Fuel pump collision switch

We may be talking two different things here (and I use both by the way). An engine oil pressure switch shuts the fuel pump off if the oil pressure falls below a set amount. The impact switch is a mechanical type of setup that cuts off the fuel pump in an impact or roll over. I use the impact switch out of the Fox body mustangs, but any semi-modern car will have one. They have a reset button if they a tripped, so no concern there. And you could just disconnect the wires and twist them together if need be, but there is really no way that would be required. Every car out there has a collection switch and I have never heard of a malfunction with one. They are a very simple mechanical device and just about foolproof.

An electric fuel pump will continue to run until the power is cut off to it! Depending on being able to turn a switch off is not a good solution to me.

They are actually called a Fuel Shutoff Inertia Switch.
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Old 02-29-2020, 07:44 PM   #6
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Default Re: Fuel pump collision switch

"B & S" - I think a "" would be more appropriate in your post than a "".
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Old 02-29-2020, 07:51 PM   #7
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Default Re: Fuel pump collision switch

Need to think about all the things that can happen in a car without air bags, shoulder belts and all the other safety devices we are accustom to! You can be the best and safest driver in the world and be hit by someone else. You can have a medical incident, etc.
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Old 02-29-2020, 08:08 PM   #8
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Default Re: Fuel pump collision switch

My solution is to not have an electric fuel pump. I don't have fuel injection. I have NO trouble running 2 97s on 1 car, 2 81s on another, 390 4bbl on my recently finished 40 coupe, certainly no problems with a concourse 40 with a 91-99 carb, with properly rebuilt mechanical pumps. I am not racing anyone with my flatheads.
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Old 02-29-2020, 10:50 PM   #9
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Default Re: Fuel pump collision switch

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Originally Posted by deuce_roadster View Post
My solution is to not have an electric fuel pump. I don't have fuel injection. I have NO trouble running 2 97s on 1 car, 2 81s on another, 390 4bbl on my recently finished 40 coupe, certainly no problems with a concourse 40 with a 91-99 carb, with properly rebuilt mechanical pumps. I am not racing anyone with my flatheads.


Goody for you no electric fuel pump however You missed the point of this post! The inertia switch is the easy solution they can be found in most wrecking yards in the trunk of older Fords that use throttle body injection systems. Usually located on the drivers side in the rear quarter area.
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Old 03-01-2020, 12:50 AM   #10
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Default Re: Fuel pump collision switch

I'm convinced. I'm going to add an inertia switch. Certainly easy and cheap enough to do. Thanks for your advice.

Last edited by JayChicago; 03-01-2020 at 01:33 AM.
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Old 03-01-2020, 08:15 AM   #11
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Default Re: Fuel pump collision switch

good choice Jay. The last thing I would want is my electric pump uncontrolled in a crash or rollover.
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Old 03-01-2020, 09:20 AM   #12
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Default Re: Fuel pump collision switch

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"B & S" - I think a "" would be more appropriate in your post than a "".
Solid point!
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Old 03-01-2020, 09:26 AM   #13
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Default Re: Fuel pump collision switch

Any FI Ford crown vic type car, on the package tray support left side, pickups usually right lower kick panel. Sometimes if you ask for Mustang parts the price goes up.
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Old 03-01-2020, 12:30 PM   #14
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Default Re: Fuel pump collision switch

I use a cut off switch mounted near the ignition switch
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Old 03-01-2020, 05:58 PM   #15
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Default Re: Fuel pump collision switch

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Originally Posted by JayChicago View Post
I'm convinced. I'm going to add an inertia switch. Certainly easy and cheap enough to do. Thanks for your advice.



Very good idea. One suggestion put the switch in a location you can easily get to so you can reset the push button when needed. You may find if you hit a bad bump or if placed in the truck and you happen to drop the lid this might cause enough surface shock to cause the switch to open. This would happen at times of Fords when the trunk lid slammed closed the shock created would cause the switch to open results car would not run.
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Old 03-01-2020, 07:46 PM   #16
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Default Re: Fuel pump collision switch

new to the idea of a pressure switch. how does it power the circuit? how do you start the car with no pressure? asking cause i;m putting an electric pump on mine.
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Old 03-01-2020, 07:50 PM   #17
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Default Re: Fuel pump collision switch

If your carburetor is good. You will have fuel in the bowl to start the car in most situations.

A inertia switch is not a pressure switch. It's made to shut off fuel if there is an impact/crash (think like a mercury switch). In the unfortunate or unlikely event you have a crash it will stop the fuel from being pumped. I use a mechanical pump, when the engine is off the fuel pump stops.


https://www.fordbarn.com/forum/showt...inertia+switch


There are better threads on installing them. Didn't find them on the first search.



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Old 03-01-2020, 07:59 PM   #18
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Default Re: Fuel pump collision switch

neither link would do anything for me. Yeah i know the diff between inertia and pressure, i want to know how to install the pressure, and yet start the car with no pressure.
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Old 03-01-2020, 08:04 PM   #19
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Default Re: Fuel pump collision switch

Please explain the fuel pressure switch you are referring to? If you are talking about the oil pressure switch. You think you need that? I guess if you had a bonneville or drag car it makes sense.


Same thing, fuel in the carb. Oil pressure will be up from cranking to start if you have oil pressure.

Last edited by Tinker; 03-01-2020 at 08:35 PM.
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Old 03-01-2020, 10:35 PM   #20
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Default Re: Fuel pump collision switch

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i want to know how to install the pressure, and yet start the car with no pressure.
Is installed on the engine to sense oil pressure, via a Tee fitting at the oil sender or the oil filter port. Is a normally open switch, closes with oil pressure. Supply wire to the electric pump is run thru this switch. If engine oil pressure is lost (like when engine dies because it's rolled over in a ditch), the fuel pump loses power.

How you prime/start the engine before oil pressure is up: A second supply wire is run to the switch from the starter solenoid. (aftermarket solenoids have a terminal for this purpose) That second supply wire is connected to the switch's pole feeding the fuel pump, bypassing the switch. While the solenoid is activated, power is supplied to the pump. Requires cranking the starter. For priming, you could do same by running a second supply wire from a dash board switch.

That was my plan for an automatic kill-switch before reading the advice from others. Now I feel the inertia switch is a better way to go. Could do both, but don't think that's necessary. The pressure switch has one advantage: will starve the engine if oil pressure is lost suddenly.
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