Wiring new fuel pump for carb conversion Options

[mb914]

Hi All,
I recently installed an engine with carburetors on a 2056. I am trying to use the stock FI wire to power the pump. I read where you need to jumper a cable from pin 30 to 87 on the fuel pump relay. I did that but I am getting constant power to the pump when the key is turned off. Any tips on how to wire the pump so that it only turns on when the key is turned on?

[GregAmy]

Circuit 30 is direct to the battery, so no surprise there. Instead, leverage the stock fuel pump relay.

Circuit 85 is keyed power and Circuit 86 is the solenoid ground to the computer. If you ground the Circuit 86 wire coming from the relay plate, wire III on the T4b plug, then the fuel pump will only be energized when the power supply relay is energized, thus only with the key on.

Do note that one of the safety features of the stock system is that it will not energize the fuel pump if the engine is not running. So, for example, your fuel pump turns off in a crash and you're upside down with the engine stopped but have not yet turned off the key.

You lose that protection when you have your fuel pump on with the key on.

[mb914]

Thanks for the help Greg. For some reason when I ground wire III on the t4b plug I’m not getting any power (12v) from the original fuel pump wire. I checked the fuse and also changed the relay. Can you think of any reason why I’m not getting power?

Circuit 30 is direct to the battery, so no surprise there. Instead, leverage the stock fuel pump relay.

Circuit 85 is keyed power and Circuit 86 is the solenoid ground to the computer. If you ground the Circuit 86 wire coming from the relay plate, wire III on the T4b plug, then the fuel pump will only be energized when the power supply relay is energized, thus only with the key on.

Do note that one of the safety features of the stock system is that it will not energize the fuel pump if the engine is not running. So, for example, your fuel pump turns off in a crash and you're upside down with the engine stopped but have not yet turned off the key.

You lose that protection when you have your fuel pump on with the key on.

[GregAmy]

For some reason when I ground wire III on the t4b plug I’m not getting any power (12v) from the original fuel pump wire.

I'm not clear I understand.

With the fuel pump removed, check for 12V at circuit 30 in the relay plate. I think that's going to be fine since you said the pump was running when you jumped 30 to 87.

With the relay installed and the key on, you should hear the pump running when you ground T4b pin III. It should go off when you turn the key off.

If there's any doubt that the power relay is working, you can remove it and jumper 30 to 87 and the pump should go on. Of course, since it's jumpered to the battery (circuit 30) then key position is not relevant.