Fuel gauge different readings

Ok I can sit in the driveway and turn the key and the fuel gauge will read 1/2 tank one time, then the next it will read 1/4 tank. It has a brand new fuel pump in it, and we were very careful with the float. Temps outside are mids 20's here if that matters.

So if you are saying you bought a pump and transferred the old float then no matter how careful you were, especially if is the original float, then just the simple transfer of the float on an old one can cause the problem. If you bought a pump and float assembly then either it is a bad new float or you may have a connection problem that took place when reinstalled wiring connection or likely a failing stepper motor at the dash cluster.

New pump and float. I really don't want to remove the pump again. Heck of a time with the lock ring.

Lifetime warranty on the pump

Just a thought.....OEM pump?

If not, it may be a generic design that meets all pressure specs for a number of GM model trucks, but the unique shape of the Avy tank may require a non linear wiper assembly on the float to compensate for subtle height changes relative to remaining fuel volume. Or, different tolerances relative to fuel temperature in the resistor assembly in the wiper could take a few seconds to minutes to warm up from the first cold start to reach a stable temperature for an accurate reading.

If it's a lifetime warranty on the pump I'd watch it a while and see if it gives consistent consecutive readings after driving it for a few minutes.

It seemed after only a few miles it was very slowly going up slowly.

It's a airtex only fuel pump with in 100 miles.

I remember something similar to this happening once when I used a non OEM float assembly on a Ford.....and it did the same thing not only on initial startup, but again after a fill up.........it not only took a few minutes to climb to a stable final reading but the needle on the 4" gauge would hunt after making a fast stop. Wasn't too important to me and I lived with it.

It is most likely the generic design of a non OEM resistance float assembly.

Somewhere in the float/fuel monitoring circuit is a dampening mechanism to buffer the reading to prevent wild needle swings when you go up a hill or make a fast turn and the fuel level changes as it sloshes in the tank........since the Avy gauges are digital this dampening mechanism is in the stepper motor circuit rather than in the resistance portion of the sending unit itself... baffles in the Avy fuel tank help to prevent this, but a generic design made for a number of different vehicles can't assume either and may overcompensate by severely dampening the needle action which would be even more noticeable on a small diameter gauge.

Start the vehicle and idle in place for a few minutes and see if the gauge readings begin to rise.......if so it is the float/sending unit mechanism probably by design.......likely will be less noticeable in the Summer with less drastic time/temperature effects as the resistance circuit warms up........and up to you whether or not it is worth it to go with an OEM pump.........I wouldn't bother since you will never run out of gas, the worst being the gauge might read lower for a while after startup.

Is it possible you have a bad motor in your cluster? If you can get a scanner to check your fuel tank level and see if it matches your displayed value you can tell if it is the sender unit or the dash cluster.

Dash cluster motor is about $15 (Saw an add for all 7 motors for like $50 on amazon)

Rodney

Could be the dash gauge and then you can yank apart the dash, but I assume you changed the pump because of a fuel supply problem and not an incorrect gauge reading, if so what are the chances that the gauge crapped out simultaneously with changing the sending unit?

Go simple first.....no scanner?.......bite the bullet and fill the tank to the top, then check the gauge reading cold to see it reads below full and stays there; correctly goes a little past the Full mark indicating no problem; or with time slowly climbs to Full indicating the gauge is operable through its range and its likely a design quirk in the sending unit. After filling the tank you can approximate accuracy by using the estimated mileage remaining readings in the DIC to calculate the percentage of fuel remaining in the tank and compare with the gauge readings when warm.