Fuel Gauge Not Working

[anoblefox]

Just finished dropping the 23 gallon (Northwest Metal Products) tank that has been service for about 30 years now. The gauge never did function correctly from the original install. It never showed more than 3/4 full and prematurely showed less than 1/4. The tank measured 13-1/4" deep and I had planned to replace the sending unit with the floatless type. I checked and the float was good and it had a range of 13 inches. I cleaned the ground point on the frame, I then added 1 ground to the frame and 1 to the body and tested the operation with my wife in the drivers seat with the key on while I moved the float from low to high. To my amazement, for the first time since the 23 gallon install, the gauge read full, and empty. No reason to get a new sender! Today I filled up with premium and everything is hunky dori. I do have a car lift, the tank was tricky to re-install by myself, but the real challenge was connecting all of the hoses. There is very little room between the tank and the frame making it difficult to tighten the hose clamps. The old girl (not my wife!) is in the best condition since I have owned her. We took the dogs out back forty to celebrate; the weather was finally good, I have not been driving for a month or so because I was trying to get the tank mostly empty prior to the removal, plus I was not sure how much gas was remaining. NOW I know how much gas is actually in the tank!

 

[jscheier]

I know this is a way-old thread, but I greatly appreciate all of the notes / comments / solutions. Gauge wasn't working on my 69 with a poly tank. Tried all the grounds, ohm tests, etc. One little comment was the solution.

Gauge is grounded to the body
Body has rubber mounts attaching it to the frame

That was it. Moved the sending unit ground from frame to body and all was resolved.

Thanks to all who take the time to share their solutions!

 

[DirtDonk]

Hey, glad you got it solved!
You could also probably have added a ground to the frame from the battery or body, but yours is probably the simpler solution.
And a ground to the frame isn’t totally necessary anyway, since there isn’t much on a Bronco that needs it.

 

[jscheier]

Going through all of the wiring over the next few months. For the most part, it looks really clean, but adding a battery to frame ground is definitely on the list! Thanks again!

 

[DirtDonk]

Sounds like the Bronco's future is bright!
If the negative battery cable was ever replaced and not duplicated the factory methodology, you'll need a couple of body grounds as well.
So make sure you have the following:
1. Ground cable to engine block (near the starter) obviously.
2. Battery negative to nearby body panel.
3. Strap/wire between the back of the engine and the firewall.
4. Anywhere to the frame. Whether from the battery, from the engine block, from the body somewhere, or wherever/whatever you choose.
5. Body to dashboard.
6. Dashboard to windshield frame (might not be needed, but you can check wiper and dome light function).
7. Body/battery to the radiator core support. Yours might be fine, but many owners end up pulling their hair out tracking down gremlins with headlights, turn signals, and whatnot, from having a poor grounding bond between the core support and the rest of the body.
Was fine when it was built, but 50 years on, it can be sorely lacking.

Your radio, lights, horns, heater and other regular components, and any oddball electronics you add, will thank you.

Paul

 

[jscheier]

3, 6 & 7 are definitely missing (or were never there).

 

[DirtDonk]

They were never there.
Ford was indeed using an engine-to-firewall ground on nearly every passenger car and truck by the time our Broncos stopped being made, but as far as I can tell, Broncos never got them until '78.
They never had one to the core support or windshield frame, because back when these were new, they simply were not needed. All the metal bits touching other metal bits were in reasonable contact and so things worked as properly as Broncos ever did.
But add 40+ years of age, rust, flex, dirt and new paint, and things don't always play nice together anymore. Electrically speaking that is...

Paul