Can someone tell me what the wires do in the frame rail loom running down the drivers side along side the fuel lines...thinking they are for the fuel pumps in my dual tank 1995 f150 xlt 4x4. Theres about 8 in there. is the thicker black wire the ground?

Trying to ground the fuel pumps somewhere on the frame rail back there. Have rfi coming through my cb antennas. Was told the ground wire to the pumps runs all the way to the engine compartment making it a big noisy antenna for my antennas to pick up. If I ground it back by the tanks on the frame it may help.

 

Yes, the larger black wire is the ground. And you can add another ground at the tank or elsewhere up the circuit but I don't know if that will totally solve your problem. You may need to place a .01uF capacitor across the pump power leads. The capacitor must connect between the plus and minus leads, not to chassis ground. This is a very common problem on numerous vehicles with electric fuel pumps from the mid 1980s to the present with Ford having issued multiple TSBs addressing the issue.

dn.

 

Thanks. I cut the black wire just forward of where the front fuel pump wiring joins the main loom going to the front of the truck. Then i grounded the pump side of the black wire to the frame ensuring a great connection. I am guessing i can just leave the other side of the black wire alone, tape it off and forget about it, or do i need to ground that too?

Still have the fuel pump noise in the cb, same level as before.

I picked up .01uF ceramic caps at Radio Shack. Which colored wires do I solder the tips across? I want to do that in the same place in the main loom, where both pumps wiring is easily accessible, if you think it'll work there. Thanks again for all the help.

 

By the way I'm referencing and trying to do what is stated in Ford's TSB


98-7-3

Check the appropriate Electrical and Vacuum Troubleshooting Manual (EVTM) (or other service

literature) for the location of the fuel pump ground. If ground is more than 0.9m (3') from the tank, cut

wire and ground fuel pump end within 0.9m (3') of the tank to prevent ground wire from acting as an

antenna. Be sure ground is secure and protected from corrosion since it is the operating ground for the

fuel pump.

The way I see it, each of the dual tanks FDMs have a ground wire that both go through connectors outside the tank and then they join into a main thicker black wire that travels along the frame rail to the front of the truck somewhere. I have the EVTM but can't figure it out. Can I just ground the main single black wire? Or do I have to ground each FDM ground wire separately?

 

The way I read that bulletin I would ground each FDM independently.

 

Well I did the black main wire, maybe I'll do both fuel pumps with a .01 cap when I replace both fuel pumps this summer, I have the bad checkvalve on the front pump and a noisy pump on the rear tank.

DO you think grounding the main black wire like I did is going to be bad? I don't want the fuel pumps cutting off the first time I hit rain on some highway! It's solid with an eye through a bolt into the frame rail, but what if it gets wet? I guess all grounds on the frame or engine block are like that too so probably nothing to worry about I suppose.

 

The whole idea of grounding each pump separately is keeping the ground length to a minimum. Grounding the main black wire is a half-fast attempt of getting around the suggested fix. Personally I think the filter capacitor is your best bet.

 

Totally agree...I'll put in the capacitor right above the tank where the wires exit when I replace the fuel pumps this summer. I don't want them in the tank exposed to fuel. Then I'm going to wrap the wires around torrid magnets from radio shack for good measure. Right now, my rear pump is flooding my cb with noise, but when I switch to front tank it all goes away. Grounding the black wire where I did must've taken out the front tank pump interference but the rear ground is still too long (over 3 feet).