ace8810

1996 f150 4.9y xl truck is new to me both fuel pumps quit working took bed off truck took fuel pumps out and they work great when connecting straight to battery. tested with volt meter at connection to fuel pumps when key turned on I have around 12v for a few seconds like I should but when I hook up fuel pumps I can feel them trying to work when I turn key on but they are not. I have cleaned connections by the fuel pumps and I don't think they are getting enough amps at the tank? What's my next step? think it's a relay?

BLDTruth

There's a relay box under the hood, one of them is for the fuel pump relay. There is another relay right next to it you can swap in to see if it fixes it (I think it is the wiper motor relay). Should be clearly labeled.

Phil48315

Do you have a good ground @ the pump ?

Steve83

Yes, it could be the relay in the PDB, and you can swap the horn relay to see if it works. Click this thumbnail:


https://www.supermotors.net/registry/media/867477_1 (for phone apps)

But it might also be any of the factory connectors between the PDB & fuel pump, including the dash switch. With everything else connected as normal, jumper the FP relay socket using a jumper wire as shown in the pic below, turn the key to RUN, then use a digital multimeter (DMM) to check voltage along the circuit from the relay, to the inertia switch (IFS), to the dash switch, to the pump. The fault is where the voltage drops.


https://www.supermotors.net/registry/media/862996

Since a '96 doesn't have that kind of DLC, you can't do exactly what the pic shows, but it takes a wire with that kind of terminal to fit into the FP relay socket. When you pull the relay, you'll see 5 slots in the socket. 3 of them are parallel to their sides; jumper from the one that's perpendicular straight across the socket to the opposite slot. A paperclip could also be made to work, with a little bending.

This shows how the circuit is built:


https://www.supermotors.net/registry/media/1116374_1