Fuel Pump Test Plug

[MummifiedCircuitry]

I'm pretty sure my fuel pump relay crapped out, when I pull the plug off the pump and put a multimeter on it, no or little voltage is showing when I turn the key and crank it. When I hook the meter up to the test plug on the firewall I'm not getting voltage either. I checked on my other montero on both plugs and I'm getting voltage when cranking as it should. My question is, can I supply 12v power to that plug on the firewall to force power to the pump or is it only for diagnostic purposes?

 

[Salonika]

Depends what you mean by “only for diagnostic purposes”. On my truck, a 98, I can use that plug to run the pump as long as I want, yes it will make the pump run. It bypasses the ignition / key circuits and supplies power directly to only the fuel pump. Now if you are thinking you have a power problem somewhere in the normal operational system, and maybe you want to run or drive the vehicle using that diagnostic plug, I have no idea……

 

[MummifiedCircuitry]

Depends what you mean by “only for diagnostic purposes”. On my truck, a 98, I can use that plug to run the pump as long as I want, yes it will make the pump run. It bypasses the ignition / key circuits and supplies power directly to only the fuel pump. Now if you are thinking you have a power problem somewhere in the normal operational system, and maybe you want to run or drive the vehicle using that diagnostic plug, I have no idea……

I mean is it only designed for sensing voltage or can it also supply voltage to the pump, essentially act as a jumper and bypass the relay. So you've personally run 12v to that wire and it powers your pump as long as the pump itself is operating correctly?

 

[Salonika]

I mean is it only designed for sensing voltage or can it also supply voltage to the pump, essentially act as a jumper and bypass the relay. So you've personally run 12v to that wire and it powers your pump as long as the pump itself is operating correctly?

Yes. It is weird when you do it because you can hear the fuel circulating. I’ve used it during fuel pressure testing once, and also to test for leaks after service where I disconnected fuel lines.