I wish my gas gauge would go all the way to FULL

[91coMANche]

No matter how much fuel is in my tank I cannot have the gauge go to full. It sits at 3/4 as a maximum. This occurred with the stock cluster and the new cluster I have in the Jeep.

[HOrnbrod]

Wishing ain't going to get 'er done. You have eliminated the cluster gauge, so the problem is either a hanging sender float in the tank, or a bad pot on the sender. Either way you have to pull the sender/pump assembly to fix. On your 91, the pot should read @ 105 ohms empty; 5 ohms full. But before you pull the assembly out, check the ground connection behind the left tail lamp to be sure it's secure and corrosion free, as the voltages sent to the fuel gauge picked off the pot are referenced to this ground.

[johnj92131]

One thing on these trucks to check is the electrical ground

 

My gas gauge was reading all over the place at various times. From horizontal below empty to past the full mark.

A fresh ground to the firewall solved that problem. This may not be your problem, but something to remember about these trucks.

[flint54]

I wished that my fuel gauge went all the way to full for a couple years before

it vexed me enough to solve it. Once I pulled the sending unit from the tank

(of my 92) it was a stunningly simple adjustment. I regret not imaging it, but

all you do is loosen a (very small) set screw, and ratchet the position of the

float/rheostat unit, tighten and reinstall the unit, and voila, full gauge with full tank!

Suggestion: put a few dabs of silicone sealant on the rubber O-ring to hold in

position while you re-seat the sending unit's lock ring (with a spark-proof brass

tool please).

 

Tom

[LarryH88bt]

Gonna hijack the thread for a moment. My gauge goes way past full and I've only got 3 gallons of fuel. I know about the ground at the tail lights which I reconnected with a fresh wire and bolt but the gauge still isn't cooperating. Any ideas? Worked fine before I pulled my tank out. If I can find the relay for the pump under the hood or the origin of the harness maybe I can reground it somewhere closer to the power.