Electric Fuel Pump shut off

37fatfender

37fatfender

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I just bought a electric fuel pump to install, but it has a caution to install it via a oil pressure switch. So that it will not run if the engine is not running. Which is probably good advise. Has anyone done it this way and what switch is best used?
 
I ran mine through a Ron Francis wiring harness, had a connection for it, put in a collision switch in the line, in this manner it is running only when the ignition switch is on, seeing as how the ignition was hot when this was hooked up this way I saw it as a good way to wire it, it does not run when you turn the key to accessory, you would burn a set of points by leaving the ignition hot, my pump is a noisy little bugger, so for me the pump is telling me, Hey the ignition is still hot ya might want to turn the key before ya go BS with your buds.
 
Here's a photo of my cut off switch. I do not use an oil filter. It's a 2 pole pressure switch with 4 wires coming off it. I use a toggle switch. To start the car flip the toggle switch "ON" and fuel pump pumps gas to carb and then press starter button and engine starts. Once engine starts I flip toggle switch to "OFF" and pump keeps pumping gas to engine. If engine oil pressure is "lost" the pump shuts off. I am not an electrical wizzard so others may have a better idea. The toggle switch under the dash is wired "between the two center terminal tabs" so that it acts as an "On/OFF switch". Two terminal tabs on the switch is "ON". The other two is "OFF." See sketch. I am using only an electric fuel pump.Hope this helps.
 

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In theory... cranking an engine will produce enough pressure to trip the oil pressure switch, thereby turning the fuel pump on.
Great idea, except... on older cars the main need for an electric pump is to "prime" the carb with fuel prior to cranking it over.
I have electric fuel pumps on every old car I have. I generally get the electric supply from the the ignition switch. I use a separate toggle/rocker switch that has a light in it so I can tell when the pump is energized. If everything is working well the pump with stop within less than 30 seconds because the system is pressured up. If the pump keeps running that means the float and/or needle valve has stuck open so I turn the pump off, wait a few minutes and turn it back on. If the system does not pressure up after a couple of tries I know I had better check things out.
I always install the electric pump as close to the tank as possible... Electric fuel pumps generally push fuel better than they pull fuel.
 
NAPA ask for low pressure Belkamp/Hobbs adjustable switch. If I remember you can get 4 to 8 psi normally closed switch.
 
Before I retired I always saved the old parts catalogs from work because they have lots of good hot rod building info in them. This is from a 2002 Airtex Fuel Pump catalog. Airtex is one of the largest suppliers of fuel pumps so you should have no problem finding this part number, Oil Pressure safety switch #OS75.

I have attached the wiring diagrams from the catalog for you. They wired the fuel pump to the starter solenoid so the fuel pump will be energized while cranking and then the oil pressure switch takes over when the starter switch is released. I think their diagram is the best way to go, there is no chance of accidentally leaving a fuel pump switch on and draining the battery down, or worse yet filling the crankcase full of fuel. The relay they are using is probably a standard Bosch style relay like is found under the hood of most modern cars. You can buy them with a little mounting tab on them. Mount the pump near the tank , it is recommended that you angle the pump like in the attached drawing. Install a fuel filter between the tank and the pump to protect the pump.

Try to purchase an electric fuel pump that is rated at the same pressure as your carburetor was designed to work with, that way you do not need to use a separate fuel regular. The less stuff that can go wrong the better! Airtex makes pumps that put out as little as 1 ½ PSI. I would go their website and view the different style pumps along with their specifications.

For some reason when I post attachments they appear small, if you click on them they should enlarge.

Jerry
 

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check out an oil pressure switch for a chevy Monza, I remember them having a oil pressure shut down, don't remember exact year, may be a little less money, and easier to find locally.Just a thought.
 
I also have an oil pressure switch to energize the fuel pump, but I used a momentary contact toggle switch under the dash for priming the carb. That way, I don't have to remember to turn it off.
 
In my search I found Holley makes a switch. Part #12-810 "Pressure Safety Switch" will shut the fuel pump off at 5 psi. They have complete installation instructions online.
cost $28. Autozone has the Airtex 0075 also for $18.
 
The best solutiion is to run a separate oil pressure switch. Small tee with a close nipple and the pressure switch. Why jeporadize your oil pressure switch. A 2-cents comment.
 
gmc1941 said:
The best solutiion is to run a separate oil pressure switch. Small tee with a close nipple and the pressure switch. Why jeporadize your oil pressure switch. A 2-cents comment.
Click to expand...
The "Pressure Safety Switch" is a separate switch. Look at the pic's you will see them:)
 
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