fuel gauge

[carolinafan4life63]

what is the best way to tell if my fuel gauge is reading correctly?? i have two gauges.......one from when it had the 6.2 i it and one that i swapped in. i recently filled the tank completly up and the original gauge read way past full...........i installed the other gauge and it reads dead on the full mark...............but i have driven it several times and niether guage seems to be dropping in fuel level...........is there any way to self calibrate a fuel gauge???? i.e. filling the tank and popping the needle off while it is running and reinstalling it to where it reads full??? or just buy a new gauge????

 

[abig84]

Its probably the ground wire. Everytime I had that happen its the ground off the tank

 

[toomany]

FWIW: GM gauges (or any stock gauge) is/are not that accurate. Add that the resistance of the sending unit may have changed some, and you get an incorrect reading.

Poping the needle off would only be a band-aid fix. The gauge only registers the resistnace of the sending unit.

I say fill the tank up, throw a 5 gallon can of gas in the back of the truck and drive till it runs out. Mark (or make note) where the gauge is reading.

 

[dyeager535]

I have come to the conclusion that GM "tuned" these gauges from the factory. Notice on the back of the gauge there is a small white ceramic piece, which is a resistor. If the colors are different, the resistance value will be different.

There is no mechanical adjustment of the gauges. Leave the needle alone, the problem is either the gauge (internal, use another), sender, wiring, or any of those three. The gauges themselves are EXTREMELY robust and very rarely fail. Based on your description and the fact that both act similar/same, the problem is highly likely not the gauges.

 

[carolinafan4life63]

ok , so i just recieved my new gas gauge from lmc today , installed it and it read correctly, it read full and i know that the tank is full , i just topped it off today also! however when i drive it down the road the needle fluctuates between just below 3/4 and full , i have checked the wires and they seem to be ok , so i was thinking maybe the sending unit is failing?? or the float is bad?? any input would be appreciated guys , thanks

 

[dyeager535]

The dampening of the needle has to be in the gauge itself IMO.

I've never seen an explanation of that function, however if you read the manuals you will see that GM states somewhere upwards of 2 minutes for a fuel gauge to register correctly after changing the float level.

From having the sending units out, I've not noticed anything that looks like it would "dampen" the signal. The float is constantly moving up and down, and when I've had a gauge fail, it bounced around over every bump, basically indicating float level instantaneously. When the gauge was swapped out, the problem went away.

If it were me, I'd test the old gauges with the resistor off the back of the new one, and see what the results are.

 

[colbystephens]

I say fill the tank up, throw a 5 gallon can of gas in the back of the truck and drive till it runs out.

if you still have a 6.2 in your truck, this is a bad idea. getting one of these restarted on the side of the road is a SERIOUS pain in the ass.

 

[toomany]

if you still have a 6.2 in your truck, this is a bad idea. getting one of these restarted on the side of the road is a SERIOUS pain in the ass.

Good catch.

1.) I don't think re-priming the system would be fun
2.) The gas probably wouldn't run too well in the motor.

 

[carolinafan4life63]

it has been converted from the 6.2 to a gas motor , i just cant get the fuel gauge to read right after , even after installing a brand new gauge , i did notice another thing , if you just switch the truck on without cranking it up , the gauge will still fluctuate , do any of you think it could be the sending unit? it is getting frustrating as hell , lol