Gas Guage Problem!! Help??

[jkade]

Went on a 100 + mile trip yesterday and my gas guage started messing up. I filled it up and it worked fine for a while and then it started moving around and going well over full. You can see in the pic how far over it has gone. What could it be???
Thanks In Advance, Kade

[gringoloco]

Looks to me like the sender wire is broken. The gauge is set up for 0ohm (empty) to 90ohm (full). If there is excessive resistance, i.e. wire broken or cut, the needle will peg, just like what you have there.

To test this, run yourself a long jumper wire from the back of the gauge to the output on the sender and turn on the key. If your needle goes back to normal- replace sender wiring.

If this does not work, maybe a bad gauge or sender, but they usually fail in the other direction (empty)

Try this and see where it gets you.

-Chris

[gringoloco]

Also, the wire may have just vibrated loose from the post on the sender. This would explain it behaving erratically before failing. It is just a little 90 degree rubber boot that pushes onto a stud on top of the tank- kinda like a spark plug boot. Very easy for it to wiggle loose.

If this is the case, just crimp it with some pliers before pushing it back on.

-Chris

[jkade]

Originally Posted by gringoloco

Also, the wire may have just vibrated loose from the post on the sender. This would explain it behaving erratically before failing. It is just a little 90 degree rubber boot that pushes onto a stud on top of the tank- kinda like a spark plug boot. Very easy for it to wiggle loose.

If this is the case, just crimp it with some pliers before pushing it back on.

-Chris

Can I get to it without dropping the tank?

[gringoloco]

Originally Posted by jkade

Can I get to it without dropping the tank?

Yeah, though it may be a pain with your truck dropped.

You should be able to reach above the tank, towards the front, on the passenger side.

Here's a pic as viewed from the front:


The large hole on top is where the sending unit is. The wire, i think, is towards the front of this.

-Chris

[gringoloco]

Wow. The one I linked to wasn't as big...

[Big Block]

If you check the voltage at the fuse block where the sending unit wire plugs in it should read around 9 volts. Just make sure if you replace the sending unit wire make sure you plug it back into the gas gage on fuse block. I accidentlly plugged it into constant 12 volt source and fried the sending unit and the wire. One expensive lesson learned.

[LUV2XCLR8]

Good advice given, Thanks Gringoloco

[jkade]

I appreciate all the info. I will let you know what I find.
Thanks, Kade

[boot85]

I had this same problem and tried a new wire and it worked,thanks

[2wdBlazer]

My bet is the ground off the tank. Happened to me.

[Burt4x4]

Originally Posted by Big Block

If you check the voltage at the fuse block where the sending unit wire plugs in it should read around 9 volts. Just make sure if you replace the sending unit wire make sure you plug it back into the gas gage on fuse block. I accidentlly plugged it into constant 12 volt source and fried the sending unit and the wire. One expensive lesson learned.

HighJack On:
Hmmmm interesting.
I stuffed my guge cluster with Autometer guages, except for the gas guage, speedo & dash lights, everything else is new...My gas guage does 'ping' past Full and stays there..I haven't had a chance to troubleshoot this yet but in the mean time I also lost ALL my dash lights...I ASSumed the whole guage cluster ran off 12v source so I connected EVERYTHING to 12v..
From your statement above, do you know if ONLY the gas guage needs the 9v or what??
HighJack Off:

Thanks
Burt

[Big Block]

It will read 9 volts because of the resistor on the back of gas gauge. Same with the temperature guage. Everything else should have 12 volts. Hope that answers your question

[gringoloco]

Originally Posted by 2wdBlazer

My bet is the ground off the tank. Happened to me.

Good call. That would have the same effect.

-Chris

[jkade]

I will give it a good looking over this weekend. I may have to change out the tank and get one with a in tank pump for the edelbrock pro-flo fuel injection that I bought to go on it.
Thanks for all the info, this is a great site.

[Burt4x4]

FYI ~ my Pro-Flo setup works great with an external elec. fuel pump...that is the way it come from Edelbrock..I don't have a stock tank..I run NWMP 37 gal tank..duno if that matters..
Good Luck
Burt

[mburgert]

Hey sorry to Hijack this one but i just reinstalled my cluster, and all the gauges work minus the temperature and gas I read above those two run off of 9 volt power but its just because of the resisters. They both all before, but the speedometer was doing the same thing as jkades. What could be wrong with the two (the needle doesnt move at all) and where is the ground from the gastank. Thanks guys

[Kantosensei]

Not to hijack, but I replaced my sender and the guage goes a little past full, but it runs empty at a little under the halfway mark. Could that mean that my new sendeing unit was bent ???? I wish it was true that I was going that far on a half tank of gas, but its not the case.