erratic fuel gauge

[shortarms]

A while ago I got some advice that my fuel gauge showing 1/4 tank when full was usually a bad gauge resistor on the back of the fuel gauge. I pulled the cluster out, intending to wire in an external 90ohm power resistor to resolve the issue. I found the nuts that hold the resistor on were loose. I pulled it all apart, cleaned and checked resistance and got 87 ohms. Close enough for the girls I chase. I reinstalled, tightened the nuts and checked resistance: 87 ohms across the posts. Reinstalled the cluster, hit the key and had an indicated full tank. I had just filled up so this was correct.

Now it gets screwy. I made it down the road about 1/2 mile and it dropped to 1/4 tank. Flipped back and forth. Settled back to full. This was last week. Now, it's pretty much back to 1/4 tank, but occasionally will flutter to full (or actual level) and then drop back down.

Loose connection from wiring to gauge circuit? I cleaned both sides with a pencil eraser and rubbing alcohol. It seems tight and straight. Bad gauge circuit? Anyone seen this before?

 

[AuroraGirl]

A while ago I got some advice that my fuel gauge showing 1/4 tank when full was usually a bad gauge resistor on the back of the fuel gauge. I pulled the cluster out, intending to wire in an external 90ohm power resistor to resolve the issue. I found the nuts that hold the resistor on were loose. I pulled it all apart, cleaned and checked resistance and got 87 ohms. Close enough for the girls I chase. I reinstalled, tightened the nuts and checked resistance: 87 ohms across the posts. Reinstalled the cluster, hit the key and had an indicated full tank. I had just filled up so this was correct.

Now it gets screwy. I made it down the road about 1/2 mile and it dropped to 1/4 tank. Flipped back and forth. Settled back to full. This was last week. Now, it's pretty much back to 1/4 tank, but occasionally will flutter to full (or actual level) and then drop back down.

Loose connection from wiring to gauge circuit? I cleaned both sides with a pencil eraser and rubbing alcohol. It seems tight and straight. Bad gauge circuit? Anyone seen this before?

i would say loose connection or your sender is bad. I would take a new sender, hook the wires to it, then play with the float. if your gas gauge reacts and follows, then play with the wires and see if it drops out. if its good, you know sender, if it flails about, wiring or that resistor you passed over(But id think the ohm test is probably right)

 

[shortarms]

yea, that's what I was thinking. just trying to avoid buying a sending unit, although i guess i'll need one sooner or later.

 

[Albrigap]

I put in a new sender in a 90 Suburban with the 42 gallon tank.
I specifically bought it for the 42 gallon but bought aftermarket.
My mistake?
Cheap ChiCom junk never has worked right since.
When empty, will take only about 20 gallons.
I has been verified as a 42 gal.
Don't be cheap as it will cost you.

 

[75gmck25]

I put new 3 port sending units in my ‘75 GMC K25 a few years ago and I got them from Autozone. I think they are a little inaccurate at the low end of the scale, but that may be because my old tanks don’t have any baffles. I still have the old 6 port solenoid, so my wiring is simpler than yours.

I have to get the truck completely level to get a good reading for about the last 1/4 tank. Ive even had it lose fuel pressure and nearly stall when going up a steep hill because apparently the gas sloshes away from the pickup on the sending unit.

 

[Albrigap]

I put in a new sender in a 90 Suburban with the 42 gallon tank.
I specifically bought it for the 42 gallon but bought aftermarket.
My mistake?
Cheap ChiCom junk never has worked right since.
When empty, will take only about 20 gallons.
I has been verified as a 42 gal.
Don't be cheap as it will cost you.

I bought the same Chineseum crap and have the same issue.
Almost empty by gauge takes 20 gallons at the pump with a known 42 gallon tank.
Gauges rarely ever give problems.
Wiring or sender is the usual suspect.