Weird Fuel Gauge Issue

[Scott Delaney]

I've searched everywhere and haven't seen anyone else post about the kind of problem I'm having with my fuel gauge.

1983 C20, 6.2 diesel, dual 20 gallon tanks.

My fuel gauge seems to be about 1/4 tank off accurate. When I fill it up the gauge reads way past full, but not quite pegged at 3:00.

When the gauge reads 1/4 tank I am empty, which I found out the hard way. Twice. Which isn't fun in a naturally aspirated diesel with a mechanical lift pump.

Now, here's the weird parts: the gauge readings are off in exactly the same way on both tanks.

Also, I disconnected the chassis ground for the drivers side sending unit and it did not affect the gauge reading. How can that be?

I suppose it could be getting ground somewhere else down the line, perhaps at the switch.

Am I correct in thinking that the problem must be in the gauge itself? And if so, what is it?

I've had this truck for three years and it's always been this way. Because the error is consistent it's easy to live with, but still I'd like to fix it.

Thanks for the help.

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[mtnmankev]

I'm curious too, my truck does the same thing and it drives me nuts.

 

[Urbanburban22]

same here 1991 Burban with a single 35gal tank

 

[Scott Delaney]

Well, we have three guys here with the same problem so I'm sure others have dealt with it.

Patience. Someone will see this and save us.

 

[RecklessWOT]

Somehow the needle is clocked in the wrong position. If it's empty at 1/4 tank and when full it reads 5/4 tank, seems that the gauge has shifted inside the housing and just needs to manually be moved. I'd fill it, crack open the cluster, position it so the needle sits at F and when empty it should be sitting at E, looks to be the same distance from E to 1/4 as it is from F to where the gauge sits now while full. I have never personally dealt with this on a square, but have had similar issues with different gauges on other vehicles, it's usually a simple adjustment (not like it reads F when full but runs out at 1/2 tank, I've been there and that is no fun). Can't possibly imagine what else it could be, not bad voltage reading or it wouldn't be consistent or even across the whole range of the gauge.

Realistically it could be a good thing though, you can use it to show off to chicks. Everyone will think you're rich because you can afford 20+ gallons of diesel when the gauge appears full, but in reality you'll only need to have about 3/4 tank to pull off that pimp daddy moneybags look.

 

[Scott Delaney]

That's exactly what I was thinking it had to be, but how in the hell does that happen in the first place?

 

[davetyp]

That's exactly what I was thinking it had to be, but how in the hell does that happen in the first place?

Heh, when you're forty years old, all SORTS of things start slipping and going out of place. Could be the needle just got slightly loose and rotated on the shaft. If you had a full tank and went jumping ditches, something like that might do it.

 

[squarelyfe]

Likely an open circuit or bad sender

 

[Bextreme04]

Mine now does the exact same thing after I removed the dual tank system and put in a new single blazer tank and sender. It worked perfectly when I had the dual tanks on either tank.

 

[Ron Sebastian]

Chiming in with my new issue. Replaced fuel switching valve, no change in surging left tank issue. Right tank has always worked without issues. Changed tank and new fuel pump, still have surging in left tank but now fuel gauge is inop for either tank. Showing full for both and I know they are not. Let the wire testing begin. But where could it be? Relay? Only thing I didn't change.