audi_maine

hey all...why is it i can hear my fuel pump turn on when i have the fuse on top of the relay with the ignition to the on position, but i can't hear it at all after i "bump" the starter? is this a sign of a bad relay? i wasn't sure if the fuse on top bypassed the relay...thanks in advance.

RussB

I forget the exact sequence, but the ECU assumes that you have residual fuel pressure, so it turns on the fuel pump only briefly when starting. Once the RPM sensors tell the ECU that the engine's running, the ECU leaves the fuel pump running.

audi_maine

so is there a typical spot where residual pressure is lost? or many spots?

RussB

Your injectors may also be leaky.

Here's a cheap way of measuring residual fuel pressure:<ul><li><a href="https://forums.audiworld.com/v8/msgs/102551.phtml">https://forums.audiworld.com/v8/msgs/102551.phtml</a</li></ul>