kevmor99

I'm still trying to figure out why my fuel pump (from a 95 F150) doesn't shutoff like most cars when you first turn the key and it builds up pressure then stops. Mine keeps going and you can hear the fuel going back into the tank. Anyone know what's wrong? I thought of putting my finger over the outlet on the pump to see if it'll stop pumping...

shoebox

Since you have a hybrid, I guess it depends on how you wired up the relay. The pcm is supposed to have control of it.

kevmor99

It's completely seperate, the relay is just switched on by the ignition and it turns the pump on, but isn't there some sort of pressure switch in the pump to turn it off?

shoebox

Nope. As long as the relay has it triggered, the pump is going to run. If you want your pcm to control the relay, use pin 7 from the red pcm connector as the trigger. You can see at the top of this diagram.

kevmor99

Oh ok, the reason why I bypassed it was because I thought it wouldn't give it power without having a theft deterrent module and the rest of the stuff hooked up. How does it know when to shut it off?

kevmor99

oh, is it a timer? So the FP runs for a couple seconds then it stops sending power to the relay?

shoebox

When you first turn the key ON and the pcm gets power, it energizes the relay for 2 seconds and then shuts it off. If you go ahead and begin to crank the engine, the pcm monitors for pulses from the opti. When it sees them, it turns the relay back on.

kevmor99

Ok, thanks!

shoebox

If you want to verify what I said was true, you could monitor the lead with a meter to see what it does (before hooking it to anything). That's what I would do. I don't even trust myself sometimes.