Why does the fuel pump on my 1990 Chevrolet pickup run with the key off.?

Answer 1

How long does the pump run for? When you turn off the motor don't turn your key all the way off. Watch your oil pressure gauge to see if pressure is still up when you turn the key off. Then watch to see if pressure drops. If so the oil pressure in the motor is what is causing it to run till it drops down pass the cut out point. It's nothing to here them run for a couple of seconds. Is this something to worry about. Yes and No. Yes, cause if your motor has a whole bunch of miles it could be clogging up the tiny hole in the pressure gauge/switch. It does two things, one for the oil pressure and two for the fuel pump. And if the hole is getting gunked up it can keep the fuel pump running until you pull the fuse out. The No part is if you have replaced the motor then you have a good oil system going for you. You can replace this dual unit, if you haven't done it before. It's a little hard cause it sits all the way in the back of the motor. Hope this helped you out.