Fuel pump collision switch

[JayChicago]

Originally Posted by JSeery

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?

[drolston]

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.

[JayChicago]

Originally Posted by drolston

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!

[Bored&Stroked]

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!

[JSeery]

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.

[tubman]

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"B & S" - I think a "" would be more appropriate in your post than a "".

[JSeery]

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.

[deuce_roadster]

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.

[Ronnieroadster]

Originally Posted by deuce_roadster

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.
Ronnieroadster

[JayChicago]

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

[Gene1949]

good choice Jay. The last thing I would want is my electric pump uncontrolled in a crash or rollover.

[Bored&Stroked]

Originally Posted by tubman

"B & S" - I think a "" would be more appropriate in your post than a "".

Solid point!

[5851a]

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.

[slowforty]

I use a cut off switch mounted near the ignition switch

[Ronnieroadster]

Originally Posted by JayChicago

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.
Ronnieroadster

[edhd58]

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.

[Tinker]

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.



.

[edhd58]

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.

[Tinker]

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.

[JayChicago]

Originally Posted by edhd58

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.

[Tinker]

Originally Posted by JayChicago

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.

A four pole solenoid does not delay or give early power to a source. You are kind, but it does not do that. 4th pole is made for direct full voltage to the coil momentary when the solenoid is acted apon. but maybe there is another 4 pole i'm not familiar with. Not uncommon. Guess you could wire it to the fuel pump also. Not sure how that's different or better. Still the same as the regular solenoid. A single power switch from the battery under the bash would be better to prime the fuel. But the only way to switch off the pump is to turn the switch off under the dash. No big whoop. Ever drive a model a with the tank at your knees.


Not sure what the level the oil pressure switches off at.


I do think you are making the best decision. It's really over thinking something.





.

[solidaxle]

JayChicago,


Your original question has got me thinking of installing an inertia switch in my car. Good idea.



Another thing to consider, If you haven't already installed one. You may want a roll over vent check valve also.

[JayChicago]

Originally Posted by solidaxle

You may want a roll over vent check valve also.

Good point! Hadn’t thought of that. Are fuel tank vent check valves readily available from the usual sources?

[solidaxle]

Rock Valley


If you don't have an opening they sell the bungs also. I would make sure you are taking the proper precautions when welding on fuel tanks.

[JSeery]

Originally Posted by edhd58

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.

If it is a 12v negative ground system it should be fairly easy to wire it up. On the original 6v system might have to get a bit creative. And I have no idea if the switch will work on 6v, but would guess it would. Modern vehicles normally have both a pressure switch and an inertia switch, but they also use high pressure fuel systems.

[oldford2]

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Originally Posted by JayChicago

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?

Getting a little carried away with what-ifs of cars tipping over, catching on fire, etc.
the more important thing in cars today are shoulder harnesses and air bags. How many old cars have you seen with shoulder harnesses? Maybe start a thread on air bag mods. I have an electric pump on our 46 only to turn it on/off to prime it if it has sat a week or 2. So no collision switch required. Maybe get your car to work like original with a fuel pump to get gas to the carb. Before you jump on me, the OP never said if he has 6 or 12 volts and asked for opinions so this is JMO
John

[JayChicago]

Originally Posted by oldford2

Maybe get your car to work like original with a fuel pump to get gas to the carb. Before you jump on me, the OP never said if he has 6 or 12 volts and asked for opinions so this is JMO

On my '40, which is an original survivor, I would not add an electric pump. The mechanical pump works perfectly well. Don't need to prime the engine, even after 6 months hibernation, just needs some extra cranking time to fill the carb bowl. Never had a vapor lock issue. See no need to alter the originality with an electric pump.

The question raised in this post is regarding a '37 streetrod. Already has been converted to 12V, already has had original pump removed and blanked off, already using an electric pump to feed a built flathead with 390 cfm carburetor. As per a post above by Duece Roadster, this engine/carb could have been fed by a good-working original mechanical pump, but all this work was already done, no point in me going back to original on this car.

[deuce_roadster]

JayChicago, Yeah, it has been my experience that I have seen electric fuel pumps create more problems (flooding, too much pressure, quit working, etc) then they solve overall. Despite wise ass comments, my intent was to show that in MANY instances, electric pumps are not needed. However If you are trying to go 200 miles per hour, they certainly would be necessary.

[JSeery]

I think we all understand an original fuel pump works fine. The question was not about an original fuel pump, it was about if protection was a good idea with an electric fuel pump. If you don't like electric pumps fine, don't use one. If you decide to run the engine on an electric fuel pump it is a good idea to have crash protection. If you don't want to add the protection then don't add it.

[tubman]

I installed an electric fuel pump on my '51 in about 1991. By 1995, I had learned a few things and removed it. I haven't looked back since. Luckily, I learned enough about automotive maintenance that I never had to resort to an electronic ignition.

[deuce_roadster]

JSeery, I COMPLETELY agree with you. Everyone should do whatever they want to their own cars. Any safety device is always a good idea. I guess I should have just put in 1 sentence stating "A well rebuilt stock fuel pump works fine most of the time"

[JSeery]

Originally Posted by deuce_roadster

JSeery, I COMPLETELY agree with you. Everyone should do whatever they want to their own cars. Any safety device is always a good idea. I guess I should have just put in 1 sentence stating "A well rebuilt stock fuel pump works fine most of the time"

And I agree 100%, but the OP question wasn't about how well stock fuel pumps work, LOL. It was a safety question. This thread seems to keep wanting to go back to stock pumps are better than electric pumps for some reason. That is not the topic, the topic is IF you use an electric pump, is it a good idea to use a safety device with it.

[38bill]

FWIW: I used the inertia switch from a old style Ford Taurus/Sable. Its fairly small and easy to remove from the donor vehicle. I also vented my gas tank since it was so hard to fill. I used a rollover valve from Tank Inc.

[aussie merc]

best solution ive come across is the relay they use with propane tanks when you key on they power up for 10 seconds [primeing time] then shut off then repower when they get s signal from the ignition coil that the engine is cranking if for any reason they loose that signal [engine stalled] they turn off