Fuel Pump 2 seconds, Fuel Pump voltage Options

[thompson-mfr]

I have a 74 2.0L original FI and the fuel pump has been moved to the front trunk. I converted to the in and out style (75-76).

My fuel pump used to go on for 2 seconds to prime, then off until cranking or running. I know this is how it is supposed to work.

Mine now is on constant with the key in aux position (before starting/cranking or running)

What controls this? The computer?

I also have only 7 volts to the pump and 9 volts at the fuse on the relay board that pump power goes through. Good 12+ volts at battery.

Finally to the question: Does the computer control this 2 second prime?

[Dave_Darling]

Ah, if it has worked for a while then my assumptions above were wrong! (IMG:style_emoticons/default/smile.gif)

Making another assumption: If nothing electrical was done to the car about the time the behavior changed, the ECU and relays and relay board and wiring are the primary suspects.

It is quite odd that any of that should fail such that the pump is on the whole time the key is on. I can see it happening if a jumper wire is added, or if the wire the ECU grounds that triggers the pump power relay gets shorted to ground. I'm thinking that may be the most likely cause.

Check for ground on the relay socket terminals for the fuel pump relay back in the engine bay. If either 85 or 86 (I forget which one, sorry!) is grounded full-time, that will make the pump run when the key is on.

--DD