Fuel Gauge stuck at 1/4 tank...

[jesus888]

So I have a JBG 23-Gallon tank and a new (5 years old but only 800 miles on it) sending unit and Autometer gauge...

In case it matters, the tank reads FULL until there are approximately 8 gallons left in the tank... it then reads @ 3/4 with 6 gallons left, @ 1/2 with 4 gallons left etc...

Everything was working fine until this week when I showed that I was @ 1/4 tank for a little longer than I expected, and when I went to put 15 gallons in the tank, the gauge never went back up to full.

It stays @ 1/4 tank. When I turn the truck off, it goes down below Empty, but as soon as I start it up and while it's running, it stays at 1/4 tank.

If it pegged at Full or Empty, I would think it was an electrical problem, but since it's stuck at 1/4 tank... I'm stuck trying to figure it out...

Any thoughts?

 

[70_Steve]

Quick test. Rmove the wire from the sending unit (if you can get to it) and the gauge should drop to below empty. Ground that same wire, and the gauge should peg full. If that's the case, then I'd say the problem is the sending unit.

Actually I'm kinda leaning towards the sending unit anyway since it's stuck at 1/4 tank. The sending unit is ~70 ohms empty, and ~10 ohms full. So how does the resistance get "stuck" at ~55 ohms?

 

[Viperwolf1]

So how does the resistance get "stuck" at ~55 ohms?

Bad ground. But it sounds like the sender isn't matched to the gauge also.

 

[jesus888]

There are definitely some matching issues... BUT, would a bad ground cause it sit at 1/4 tank?

 

[Viperwolf1]

There are definitely some matching issues... BUT, would a bad ground cause it sit at 1/4 tank?

It could, especially if there is a mismatch.

 

[jesus888]

OK... I'll take a closer look when I get home tonight... fingers crossed that it's somethin easy...

 

[broncomatt]

I've been having a simular problem with my main and aux senders. Both are from Jeff's.
The main reads full when ever it has more than 6 gallons, drops quickly down as it gets to E, and E realy is empty. Stock guage too. My aux tank only reads empty. Still looking into the ground on that one but both senders are less than 6 mounths old.
If your setup worked before now I would drain the tank and look at the sending unit.
May be a bad batch of senders from Jeff's.

 

[jesus888]

Well I checked on the ground for the actual gauge and everything on that side seems to be fine...

Upon cursory inspection under the truck, the ground looks good for the sending unit... Looks like I'm gonna disconnect and connect that ground tomorrow and see what happens...

On a separate but related note... What's the mechanism at gas stations that makes it shut off when it's full AND is it pretty likely that it'll work properly with our old filler necks? Always nervous it's gonna overflow while I'm pumping, however little it is