bad ground

[ericwade381]

I have a bad ground that is throwing off my fuel gauge wanted to see what wire I need to cut to slice in to put another new ground on the frame of the truck any help would be great thanks guys!

 

[IDIoit]

Ground = 12V - theres only one that goes to the FVS IIRC

 

[ericwade381]

I think it's the black wire iirc

 

[ericwade381]

Watch "how to fix a fuel gauge problem for ford and many more" on YouTube
how to fix a fuel gauge problem for ford and many more: http://youtu.be/Gg1O_SKIljI

 

[laserjock]

There's two wires going to the sender. What you really need is to ground the tank most likely. For a quick fix, clean off a little spot on the return tube near the base with some sand paper or emory, strip a piece of wire and hose clamp it to the tube. Then bring it over to the frame and clean off a little spot and put a ring terminal on it and screw it to the frame. Again clean off a little spot. Check your body grounds too. There should be a ground strap that runs from the front driver cab mount up to the body. Mine was rusted out. There should also be one on the fire wall. Check the grounds from the battery to the frame/body too. The engine block is grounded.

 

[ericwade381]

thanks guys I did the trick that you said to do on the sending unit however my gauge did not move :-(

 

[laserjock]

You are going to have to start going through the wiring and figure out where your problem is. Did you try grounding the sender wire in your connector? If you ground it and the gauge doesn't move, you probably have a cluster problem. If the other things haven't worked, you've got to start working your way through things systematically or you will never figure it out. Find one of the schematics that's been posted here lately on the fuel selector valves, pull the connector off and tie the signal pin. If the gauge doesn't peg one way or the other (full I think) it's a gauge or wire to the cluster problem. If it checks out, jump the sending units from the tanks to the signal pin and see if they read. If they do, it's the fuel selector valve. It really is a pretty simple system. If the gauge is good, everything else is easy.

Edit: Did you check your chassis ground straps? If the cab isn't grounded well, grounding the gauge won't do anything. Check it with a multi meter by checking the resistance between the neg battery terminal and the cab (pick a bare spot or a sheetmetal screw on the firewall). If the ground straps are missing there is nothing tying the cab to the frame electrically because of the rubber body mounts.

 

[ericwade381]

Thanks for the reply on this issue. What is usually the best way to ground the pin a wire inside the connector and run the other end to the frame? I tried that and my gauge is not moving when I do this as my wife watched as I did it. I'm starting to think it is my gauge do these go bad or only if a wire to them is bad or problematic?

 

[ericwade381]

I will have to see what my straps look like as well

 

[LCAM-01XA]

If the ground straps are missing there is nothing tying the cab to the frame electrically because of the rubber body mounts.

Go take a look at the radiator support in the area in front of your driver-side battery, and rethink your statement. Bricks have a grounding stud there, lots of body harness grounds hook up to it but it also grounds the front clip and therefore the cab. Chassis grounds are worthless on these trucks, you're better off running a nice heavy ground from the steel skeleton of your dash straight to one of the batts. Then you can add individual grounds to the dash skeleton if so needed.

 

[laserjock]

Do the other gauges work?

Here's what I would do.

1. Take your ohm meter and check to see if the frame is grounded. Touch the neg post to the frame. Dig the probe in good. You should have almost no resistance.

2. If that checks out, same test to core support.

3. If that checks out, same thing to fire wall. Try a couple different places.

If that checks out, you have now determined that both the frame and cab are grounded. I'm assuming since the truck starts and runs, the block is grounded. If something didn't check out, fix it by putting ground straps on or fixing the ones there until it does.

With all those checks done, you should be able to take a jumper wire and jump the signal pin in your selector harness to ground your gauge should peg out. If it doesn't, your problem is between that connector and the gauge. If it does proceed.

Plug the selector back in. Put it on the front tank and unplug the sender from the tank. Ground the signal wire by shorting across the 2 pins. If the gauge doesn't peg, ground the signal pin to the frame. If the gauge doesn't move, the selector or wire to it is the problem. If it does, there's a problem with the other side which I think is a ground. You are doing these tests key on engine off right?

That's about all I can tell you. You can do the same at the rear tank. If niether work but the gauge checks out it's likely the selector.

Work your way through from one point to the next in the system until you find it.

 

[ericwade381]

Thanks! I have done the checks with the key in the aux position and also in the off position same thing no change. The gauge does not move when you flip to go to front or back tank. I noticed once the truck was running I flipped the switch and it was very slow switching even stuck for a minute then moved again. This last time filling the truck the gauge stuck on 3/4 and has not moved at all.

 

[ericwade381]

Also my oil pressure gauge acts funny sometimes

 

[ericwade381]

Does the fuel gauge have a *main* ground on it? Somewhere

 

[laserjock]

I think you need to do the checks with the key in the on position. That may be part of your problem. I don't know if the gauge is live in the aux position. I don't think it is.