Gas Gauge

[newjack42]

Gota 99 silverado and the gas gauge reads funny when you start the truck and the tanks below half. Above half a tank and its just fine but below it will always seem to read a qauter tank lower than it really is. Some times it will bounce back were it really is by the time i get out my driveway sometimes it will take anywhere from 5 to 50 miles. What the hell is goin on here???​

 

[Zembonez]

My bet is the sending unit. Have you ever replaced the fuel pump? If this is a GMT800 truck, there were also some issues with the instrument clusters...

 

[Stumpuller6.5]

clusters are know to be an issue with those trucks, only way to varify the sending unit is to remove cluster and ohm the wires from the sending unit, see if the readings change at all, IIRC, 60 ohms is a full tank...and empty is coser to zero, not 100% sure tho.

 

[newjack42]

Yes it is a GMT800. And i put in a fuel pump about a year ago. it started actin up about 3 months after i put that in too

 

[Stumpuller6.5]

check your connections and the gound on the frame. (if it has one, I know the GMT-400s have a ground close to the tank...)

 

[mr_bots]

Both the clusters and fuel sending units were big problems with that generation. Everyone I know that's had a 99-06 chevy/gmc atleast had one of those fail. Parents' 01 Silvy had the sending unit fail after warranty and just went by the odo, their 03 Yukon went through two sending units under warranty, and screwed up again at about 60k and went by the odo. Brother's 03 Sierra had the sending unit fail under warranty, the cluster fail out of warranty, and the fuel pump fail out of warranty. Aunt's 01 Tahoe went through 4 sending units before she sold it...you get the picture. What's really cool is if it's idling and the gauge drops to empty jerk the steering wheel back and forth and it'll jump back to normal. Guess the increased load from the pump raised voltage