99 Yukon Fuel gauge always reads"full"

[Dryfly]

I have a 99 SLT 4-door 5.3 Yukon. The fuel gauge is always on full unless the the vehicle is turned off-then it goes to "E". When filling the tank it jumps to about 3/4 and vibrates. When the tank is full gauge goes back to "F" and stayed there. I replaced the cluster with one from from a junk yard and it didn't help.

Am I looking at a sending unit? I also suspect fuel pump issues so I guess I'll find out when I replace the unit but I understand that sometimes these issues are gauge problems rather than float or sending units.

 

[SunlitComet]

Possiblybut you should note that the sender on your year goes thru the pcm first so if you do measure the senders resistance or ohm load the gauge for testing purposes use the wire prom the pcm connection to the component to do the testing. That way you can find out if the pcm might be screwy if it is not the components or their wiring.

 

[CHEVHEAD78]

When I worked at Auto Parts Store.

I used to pick up chevron with techron at any auto store make sure it has the de-sulfuring additive for fuel senders neighbor used to get me to pick it up every month for him when his was on the fritz then one day it just stayed working.

 

[Dryfly]

I replaced the fuel filter/sending unit/fuel pump unit at the tank. That fixed the gauge problem. Since I haven't gone through a tank of gas yet, I can't tell if the gauge is accurate at all levels, but it seem to be about right for the level that the fuel is at now. I'll know better as I get closer to empty. I'll carry a gas can with me until I know for sure. I would like to see that the gauge reads "E" when it's supposed to.

 

[aaronr511]

Just want to throw this out there I know this thread is 10years old, if you change the cluster bulbs the housing for the bulbs transfer power for the gauges. So if the bulb housing isn't making proper contact i.e fuel guage will read pass full also.

 

[Eman85]

Just want to throw this out there I know this thread is 10years old, if you change the cluster bulbs the housing for the bulbs transfer power for the gauges. So if the bulb housing isn't making proper contact i.e fuel guage will read pass full also.

Basically any open in the circuit will cause a full reading, a short to ground will cause an empty reading. The tank unit is a variable resistor to ground.