Blender

I believe I have a fuel pump or relay problem, Car has been hard starting, lots of cranking and sputtering but then runs nicely once it gets going.
Today NO GO, Just an occasional sputter.
When I turn the Ignition on, NOT CRANKING, I can hear the Fuel Relay and Pump start but then stop several seconds later.

Is this normal or should pump keep running.
What is the function of this relay and How is it controlled, Pressure cut off, overload etc?
Thanks

Blender

RIPSAW

The pump runs on a timer (probably in the start relay) for the brief few seconds you hear at the first key on before you hit start. This is to build up pressure for the start. Once running, it gets the signal from the ECM that the motor is running (from the crank position sensor) Once running, the pump runs all the time. The excess pressure is bled off (from a relief valve)and recirculated back to the tank. That way you have a set pressure at all time, be it idle or WOT) This is all for safety since if motor dies, you do not want the pump to run just with key on.

Blender

Thanks for the description, Relay seems to be working then so it may be the pump not building pressure.
Filter is only 3 months old.

Blender

ezone

I'd get a test light and connect it to the pump feed wire. This can be done at the tank or right at the main relay.

Monitor if the pump is getting powered up at the correct times.

Pump runs at first key on for about 2 seconds (prime mode), then shuts off.
Pump runs again during cranking and during engine running.


PGMFI main relay is a known problem area. It can fail by not running the pump at the right time, and it can fail by not powering up the ECM (check engine light does not come on).
Fuel pumps usually are damn reliable.....they didn't use parts from GM. LOL