Technical Electric fuel pump safety switch controlled by tach signal-who’s done it?

I am installing an electric fuel pump on my ‘57 Chevy truck (350, Edelbrock carb, aftermarket tank behind rear axle)
I want to wire it safely and am considering Revolution Electronics tach-signal controlled shutoff (as opposed to an oil-pressure switch)
Does anyone have experience with this setup?


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I used the oil pressure switch, didn’t know of such a thing

 

I have experience with a pressure switch, which works, but doesn't have that 3 second prime feature. Sounds like this is a neat solution, give it a try and let us know how it works.

 

I'm trying to understand the tach/fuel pump connection. Does it shut off fuel pump over a set r.p.m.?

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I’m thinking it’s setup to stop the fuel pump if there’s no tach signal. Engine is stopped, don’t try to push fuel to it.



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that's what it says on the web site for the device. No tach signal = no fuel pump power

 

I'm interested in this also, I have a non Hamb EFI going in my 57 and was just looking at pumps. A friend offered to give me a in line pump (barely used) because he didn't like it. He was putting one in tank. So I read up on them and the way to go is in tank. Now I just went to the web site for Revolution Electronics and like what I read.

Pat

 

Yes, as I understand it, the controller runs the pump for 3 seconds to prime the line, then looks for a tach signal (square-wave) in order to keep the pump powered. If the motor stops, the controller shuts the pump off.


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I installed a oil pressure switch for my electric fuel pump using the switch recommended in this article:
http://www.how-to-build-hotrods.com/electric-fuel-pump.html
The switch allows the pump to work when the ignition switch is in the “start” position and in the “on” position only when there is oil pressure. I wired the switch and pump through a relay.

 

As I understand what you want to do. The engine will start an run on the carb bowels and when the tach shows power to read from the coil the pump will start running. If your wiring the pump to the tach feed the wire size on the tach is too small. I could defiantly see this being done if the voltage to the tach from the coil could actuate a relay and I would try this first.

Now the reason not to do this is the engine will run out the gas in the bowels where a loss in oil pressure will immediately cut the feed to the ignition.
On my race car I have a 30 psi oil kill for the ignition and a bypass switch so it will start immediately if I want. Once running at 50-60 psi I turn off the bypass so it will kill it under 30. Some do it at a lower pressure. I've used one 20 years before it was mandentory where I race.

 

He's planning on using this device

https://www.revolutionelectronics.com/Products/Fuel_Pump.html

to control the pump. The black box connects to the tach signal, and uses that information to power a relay that runs the pump. The pump won't be powered by the ignition system directly.

 

I run one on my OT modified vehicle.
It runs a high pressure EFI pump.
They are known as Tachometric relays in Australia and they are used on cars running gas (the vapour not the liquid) and are wired such that they receive a signal from the ignition circuit that keeps the relay engaged. Once the ignition stops the realay drops out and stops the pump.
It also runs the pump for a few seconds on start up but will cut the pump if you turn on the ignition but don't try to start the engine.
This will tell you a little more about them.
https://www.google.com/search?q=tac.....69i57j0l7.4862j0j7&sourceid=chrome&ie=UTF-8

Cheap as chips for what they do. I actually have one in my junk drawer as I purchased it and didn't use it.

 

I use a forklift propane safety switch, primes for 3 seconds then shuts of until it gets a signal from tach wire or coil neg.

 

How about a Murphy gauge to power the pump

 

Well, I ordered one. I’ll let you guys know how it works.
It’ll be powering a Carter pump and feeding an Edelbrock carb thru a Jegs fuel pressure regulator.
Wish me luck..


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Guess I’m to old fashioned to know about this stuff my modern dd’s have Jim....

 

That's fine....which is why I answered the question as I did. I figured you were not aware of this

 

Back in the '80s a friend crashed his '32 panel truck and was knocked unconscious. Engine quit but electric fuel pump fed the fire. He died and it was a preventable loss. I run an electric fuel pump on my 3W with a pressure switch and an over ride to prime the carb. As the old saying goes, safety is no accident. Take as many precautions as possible when building your hot rod. I like the product that 57chebbie is considering, but the pressure switch will still be my choice due to the simplicity and cost.

 

It seems like it would be less expensive and less prone to failures (simplicity) to use an oil pressure switch (this Summit one switch closes at 6psi I believe). Fuel pump -- ground to this and a toggle switch under dash to ground. Pump + to ignition switch.
With key on, flip dash switch, pump runs.
Once car starts, flip dash switch off.
If oil pressure drops below 6 psi, fuel pump cuts off.
Dash switch is handy (engine off) if you want to run pump to check pressure, set float levels (Holley), check for leaks, etc.

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Never used one but I like the idea

 

I've seen oil-pressure related switches and now tach/electric switches to shut off fuel flow. My '37 Chevy has a Ron Francis inertia fuel shut off switch but it has not been tested in real life.

Any thought about how or if one has more safety points than another?

 

if you want to be really safe, you'll sell your hot rod.

But you could use all 3 switches, if you want.

 

I run these on all my vehicles with electric pumps (or propane fueled systems). They will also handle the current draw of an electric fuel pump, so no need to fit a relay.

 

As I mentioned, fuel pump gets power from ignition switch when on. Fuel pump gets ground via oil pressure switch and dash SPST toggle to ground. Pump runs only when key is on, dash switch is on. Once engine is running, flip switch off. Pump runs as long as there is oil pressure over 6 psi. If pressure switch fails, turning dash switch on runs pump (getting car home).
I like simplicity.
Our cars either have mechanical pump or the electric pump ones don't have safety...key on, pump runs.

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My grandson was fortunate. His F150 burned when he hit a ditch, broke the engine mounts, and fuel line. He was not knocked unconscious, but lost his truck because the inertia switch didn't trip on a vertical shock (dropping in the ditch at speed), as it is intended to react to a deceleration.

I'll still use an inertia switch though, because the engine may run with a fuel leak after a collision.

 

For those who don't recognize the 3 prong oil pressure sensor (PS-64) in the "How to Build Hot Rods" article it was original equipment in the Chevy Vega & Monza. IIRC, the 3 wires to that sender were heavy guage and it ran from the sender to the fuel pump without a relay. They never gave many problems, if you used it to engage a relay it would probably last forever.

Lou

 

If I'm not mistaken, the 3523608 (and others I don't have the number for now) fuel pump relay for many versions of Volvo 240/740/940 has these functions - it runs the pump for a moment at first, and after that only when it gets rpm signal from the ignition. I'm sure similar relays are available in other 1980s/1990s cars.
Perhaps a good solution for someone.

 

Uses the traditional 3 prong headlight pigtail.

 

It's like having a crank position sensor for your old car, should work good.

Mine stops pumping when the engine isn't spinning.....but will gravity if the line is broken between it and the tank.

 

"if you want to be really safe, you'll sell your hot rod."
...Words of wisdom!


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