Fuel pump test jumper - 94

[Camaro1976]

I was having issues with my fuel pump. Replaced fuel filter and it was fine. Checked relay and it was fine. When I have the jumper pin plugged into the diagnostics port it runs fine and I can hear the pump working all the time. Are there any longtime negatives to leaving the jumper plugged in all the time? Truck has 240k and I don't drive it much because I have a bike. Otherwise, what else could possibly be the problem?

 

[RotaMan2]

Did you test for voltage at the pump? Or from key to relay? If you are getting the pump to work by jumpering it then, I think its a issue with the key to relay circuit. Jumpering it bypasses this. Good luck.

 

[turboSR5]

One thing to be concerned about when leaving it jumpered..if you get in an accident and you are unable to turn the key off..you could have quite the large amount of flammable liquid surrounding you and others. Under normal operation your fuel return line will just route the excess fuel back to the tank.

There could be a problem with your AFM. The fuel pump gets a signal from the AFM when the flap door opens and turns on the pump.

 

[fourwd1]

Jumping the terminals bypasses the AFM switch and the Circuit Opening Relay.
Relays don't fail too often, so you may want to check the switch in the AFM.

 

[Camaro1976]

I tested the resistance specs of the AFM and it passed the static and dynamic tests. The problem is progressively getting worse with time. It used to be only at a few stoplights, then got worse, and now it won't run for more than 10 seconds.

Sounds like bad contacts in the relay to me?