Fuel pump collision switch

[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.





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[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