Fuel Gauge

[Coffee Roaster]

My 1976 Chevy Scottsdale, the fuel gauge once off full the needle bounces, can not tell how much fuel remains. Is this a ground problem or the actual sending unit. Please advise thank you all

 

[bucket]

Only while moving? Or when stopped too?

 

[Coffee Roaster]

moving mostly

 

[Ricko1966]

My 1976 Chevy Scottsdale, the fuel gauge once off full the needle bounces, can not tell how much fuel remains. Is this a ground problem or the actual sending unit. Please advise thank you all

The sending unit is the ground. You can look up the resistance value of the tank at 1/2 full. Disconnect the sender and use a resistor, or pot of the proper value to ground and go for a drive,you should get a steady 1/2 tank reading. If you do not get a steady 1/2 tank reading it's a wire or the gauge itself. If you get a steady reading it's the sender. 0 ohms empty 90 ohms full so a 45 ohm load will tell the story.

 

[fast 99]

The sending unit is the ground. You can look up the resistance value of the tank at 1/2 full. Disconnect the sender andvuse a resistor,pot of the proper value to ground and go for a drive,you should get a steady 1/2 tank reading. If you do not get a steady 1/2 tank reading it's a wire or the gauge itself. If you get a steady reading it's the s

Wonder if it's sweeping too fast/much like a bad resistor?

 

[bucket]

Saddle tanks tend to slosh a lot. The gauge has a resistor strip of some kind across the two terminals, on the backside so that the needle doesn't swing around as much. It could be bad.

 

[Sad Sack]

Maybe clean reseat the fuel gauge contacts and re-evaluate.

 

[TotalyHucked]

Could be normal, mine would bounce pretty good once I got below 1/2 tank with the original, non-baffled tanks

 

[Sad Sack]

Could be normal, mine would bounce pretty good once I got below 1/2 tank with the original, non-baffled tanks

Mine does the same thing when past half. Damn gravity screwin' with the needle!

 

[Coffee Roaster]

Saddle tanks tend to slosh a lot. The gauge has a resistor strip of some kind across the two terminals, on the backside so that the needle doesn't swing around as much. It could be bad.

I only have a single tanks

 

[Coffee Roaster]

it appears I need to take the bed off to get at the unit and terminals. BTW it bounces even at idle

 

[Coffee Roaster]

Only while moving? Or when stopped too?

even stopped

 

[bucket]

I only have a single tanks

Long and skinny tanks outside the frame are saddle tanks. You just have one saddle tank

 

[Ricko1966]

You could unpin the pink wire at the bulkhead connector and run your resistor there.

 

[Broken85]

The sending unit is the ground. You can look up the resistance value of the tank at 1/2 full. Disconnect the sender and use a resistor, or pot of the proper value to ground and go for a drive,you should get a steady 1/2 tank reading. If you do not get a steady 1/2 tank reading it's a wire or the gauge itself. If you get a steady reading it's the sender. 0 ohms empty 90 ohms full so a 45 ohm load will tell the story.

I don’t think the sending unit is the ground, there should be a ground wire that runs from the sending unit to the frame. The tank just sitting in the saddles would be a terrible body ground. It actually sites on rubber or tar paper in there from the factory to prevent squeaks.

If it is bouncing from full to zero constantly, sounds like a ground wire problem. You could try to run a ground wire from the frame to one of the flaps of pressed welded tin on the tank with a self-tapper and see if it fixes it. Of course if there is a lot of corrosion around the sending unit where it meets the tank, this won’t work, but it’s easier than pulling the bed off as a first step and the sending unit is under the cab anyway, not the bed so the way to do it is drop the tank.