Another gas gauge thread...
 

I have seen a few, but none doing exactly what mine is. Basically the needle points at full or a little beyond and then when the key is turned on it moves to 3 o'clock (way past full). I looked under the truck since many threads say to check the ground at the tank. There was a purple wire grounded to the inside of the frame just under and to the front of the tank. I'm not sure if that is for the sending unit, but I went ahead and removed it, cleaned it, and reinstalled it with no luck. I also cleaned the one that goes to the filler neck - just because. Any advice before I pull the cluster????

Re: Another gas gauge thread...
 

if your gauge is going to 3:00, sender wire is crimped, broke, etc. trace your sender wire from the switching valve to the firewall. usually they get damaged in that area

Re: Another gas gauge thread...
 

Also if its a dual tank check the passenger side wire also might be a brake there

Re: Another gas gauge thread...
 

It only has a single tank. Any idea what color wire it is - I know "get a damn manual". If you know off hand I would appreciate it.

Re: Another gas gauge thread...
 

What year is your truck?

73 - early 78 use a tan wire for the fuel sender.
late 78 - 87 use a pink wire for the fuel sender.

Re: Another gas gauge thread...
 

85 - so I am looking for a pink wire - thanks!!!!!!!

Re: Another gas gauge thread...
 

I wonder if that changed with the fuse box,tube to blades?
(my 78 is tan and tubes)
if the cluster has been changed sometimes the wire needs to move spots(my 78 did)
with sender wire off, goes over full,grounded goes to E

Re: Another gas gauge thread...
 

Needle at 3:00 means;
The ground has come off the frame or sender ring...
The sender to gauge wire has been damaged...


Manuals? Look down. :D

Re: Another gas gauge thread...
 

Thanks man!!! Your wiring diagram link confirms I am looking for a pink wire for signal and the purple wire I found is the ground.

Re: Another gas gauge thread...
 

Sorry to hijack your thread but I'm having a similar problem.
Would the same wire be the same color on an 87 454 TBI suburban?

Re: Another gas gauge thread...
 

This sounds like it could be what's wrong with mine. Gotta check mine out now.

Re: Another gas gauge thread...
 

Found a brown sure coming from firewall about 10 inches long and it has a black plastic plug on the end that's not connected to anything. Could that be for the gas tank?

Re: Another gas gauge thread...
 

Yes, look for another " mate" to fit , try the tank frame rail area

Re: Another gas gauge thread...
 

the easiest way to check if it's your sending wire, cut the wire as close as you can to the switching valve, then cut the wire at the firewall & tie in a new piece of wire. when i put my truck together a few yrs ago, i heat shrunk the wires, covered them in insulation with zip ties, then bundled them & zip tied convoluted tubing to them, then clamped them to the frame. good for longevity, lousy for finding any breaks, thats why i did mine that way.
just stuffed the new wire in the tubing. last yr i got ambitious & fished out the old wire, sure enough it had got sliced by a clamp:dohh:

Re: Another gas gauge thread...
 

I meant a brown wire. I will post a pic of it later in the day. I sure hope that's all it is that's wrong is it's not connected

Re: Another gas gauge thread...
 

Here is the wire I am talking about with the plastic clip type connector thing at the end. So this is defintely the sending unit wire coming from the firewall? It lines up with the instrument cluster. It may not look like its tan in color in the pic but it is. My truck is a 1974 c10. So all sending units have this connector?



http://images2.snapfish.com/23232323...C7%3A239ot1lsi

Re: Another gas gauge thread...
 

I got a 74 K10 with a 350 and turbo 400 and my gas gauge moves all over the place, I just try to keep it topped off.

Re: Another gas gauge thread...
 

different plug and shorter wire for the 74 then,not what i was looking for,my 78 Jimmy it ran behind the dizzy down the pass frame
with an add on piece to the tank

Re: Another gas gauge thread...
 

I traced the wire from the tank along the frame rail and as it gets up by the passenger side spring it is pinched between there and a bracket. So I had to go up top above engine and look down for it and nothing's there. Previous owner must have done it without realizing it. Guess I gotta cut it then add to it and see what happens

Re: Another gas gauge thread...
 

The 1974 GM wiring diagrams will show wire color, wire gauge, and which cavity in the Packard 56 bulkhead plug is for the fuel gauge sender wire. The original plug on the frame rail is a molded rubber piece.
I'm not sure what that Packard 56 plug in your picture goes to.