Carbs and fuel pump relay, my solution Options

[hcdmueller]

I am running carbs on my 2056 so I performed the simple mod as described by SirAndy in the Tech Articles. One thing I have noticed with my car is that my fuel pump runs continuously with the key switched on. The fuel pump is a rotary one that I bought from the Type4Store.

I didn't like that fact that my pump kept running so I took matters into my own hands. I modified a Bosch CIS fuel pump relay to work with my car. It needs a signal from the negative side of the coil to provide power to the fuel pump. So unless the engine is cranking or running it won't start up the pump. Nice to have the extra safety margin as well. The relays are easy to find in the junk yard. I only paid a couple dollars for 3 of them.

[shane]

I am running carbs on my 2056 so I performed the simple mod as described by SirAndy in the Tech Articles. One thing I have noticed with my car is that my fuel pump runs continuously with the key switched on. The fuel pump is a rotary one that I bought from the Type4Store.

I didn't like that fact that my pump kept running so I took matters into my own hands. I modified a Bosch CIS fuel pump relay to work with my car. It needs a signal from the negative side of the coil to provide power to the fuel pump. So unless the engine is cranking or running it won't start up the pump. Nice to have the extra safety margin as well. The relays are easy to find in the junk yard. I only paid a couple dollars for 3 of them.

Was going to hook up my carb fuel pump today off my oil pressure sender today and was reading about my options here. Haven’t got out my multimeter yet but this seems to make sense, is anyone using this method or a reason this method doesn’t work or is a bad idea. Thanks.

[DickSteinkamp]

Was going to hook up my carb fuel pump today off my oil pressure sender today and was reading about my options here. Haven’t got out my multimeter yet but this seems to make sense, is anyone using this method or a reason this method doesn’t work or is a bad idea. Thanks.

If it is a pressure switch that turns the green light on and off, yes, it will work. When no oil pressure you can wire it to ground the fuel pump and prevent it from running. However, you will also need a signal from the starter when it is turning to power the fuel pump so that it will provide fuel to the carb if the float bowl is low. This set up is commonly used in boats to prevent an electric pump from continuing to run if a fuel line breaks.

If your oil pressure sending unit is for a gauge, no. That sending unit is a variable resistor based on the pressure it sees, not an on/off switch.


In Shane's example, isn't the pump going to continue to run if the engine stops in a position where the distributor is energizing the coil? (Or am I too hung up on points type ignitions?)

[shane]

I do have points, I’m thinking you are correct if I run the fuel pump relay off the negative side of the coil and the points are closed when the engine is off the pump would continue to run. But wouldn’t it also be a constant pulsating ground? Idk if the relay cares much or if it’s going to shorten the life of the relay and pump? Sounds like I’ll just keep it simple and run the relay off the stock oil pressure switch. I have a freshly rebuilt carb I’m thinking I’ll always have the tiny bit of gas it takes to start the engine and turn on the pump.