help! fuel gauge kind of works?

[Hyperballsmcgee]

posting under electrical cause I figured this was a wiring issue. the gas gauge in my 74 Scamp is all the way down, then when the key is turned it moves up to E but doesn't go past that. I filled the tank two days ago and it was still on E. what's got me stumped is that it goes from resting position up to E when the key is turned. all fuses checked out with a voltmeter. any suggestions? I have zero experience with fuel sending units and very little with wiring.

 

[mopar head]

Make sure your ground strap is still on or not rusty giving bad connection.
This is a little metal strap clip located off your fuel tank sender, it spans a short piece of rubber hose, then to the metal fuel line.
If OK, maybe your sender float has leak and sunk. also pull and check sender, make sure the fine rheostat wires have`nt broke.
I`m guessing 74 still uses this system as 67 does.

 

[RedFish]

I have a pic of one possible cause here somewhere. There is a brass contact in the sender that slides on a resistor wire. After 40 years of wear what was a stamped spot becomes a fish hook of sorts. It will catch the resistor wire and stay caught right there.
Other common cause is a saturated float. Those get a tiny hole in them and fill with gas.
In either case the sender is not functioning. The gauge is working exactly like it should,
2 needle positions, home, empty.

 

[mvh]

I had the same issue, though I didn't pull it until after the "hook" had torn through the wires, making it non-functional.

I'm not sure how you'd fix this particular issue. You could trim off the old contact, cut a new piece of brass and rivet(?) or braze it in place, I guess. A little tricky with paper-thin 45-year-old corroded brass.

One thing, don't buy one of the "new replacement" fuel senders -- they are complete crap. They were designed for a different model, and have a different pivot point and sweep to the float arm, so they read "full" with 8 or 10 gallons, and never reach "empty", which makes them pretty useless.

Better to find somebody who is changing to 3/8 fuel line and get their old sender -- that is what I had to do. A new float and screen and it was good to go.

I have a pic of one possible cause here somewhere. There is a brass contact in the sender that slides on a resistor wire. After 40 years of wear what was a stamped spot becomes a fish hook of sorts. It will catch the resistor wire and stay caught right there.
Other common cause is a saturated float. Those get a tiny hole in them and fill with gas.
In either case the sender is not functioning. The gauge is working exactly like it should,
2 needle positions, home, empty.