Strange fuel guage problem
Thread Starter
Instructor
Joined: Jun 2015
Posts: 178
Likes: 34
From: Calgary Alberta
Strange fuel gauge problem
I have a problem with the fuel gauge on my '81 and I can't find anyone else who has had a similar problem.
The gauge itself appears to work fine. It points right at "F" right after I have filled the tank (though it comes off that mark very quickly - after about 20 miles). The gauge sweeps evenly all the way to empty and comes to a final rest just counter-clockwise of the "E" mark".
This is where is gets odd. When I refill my 24 gallon tank (well, that is what it is supposed to be) from when the gauge shows empty I can only put about 16 gallons back in. I have crudely measured the amount of fuel in the tank by dropping in a wooden dowel and find that there is about 1/3 of a tank remaining when the gauge read "E". I have put an ohm meter on the sender (while it is still in the tank) and see that it reads as it should (89 ohms at full, 51 ohms at half-ish and 0 at empty).
I thought that perhaps the float arm might have been bent, but can't conceive of a situation where bending it would cause it to show empty with a lot of gas in the tank, to read full when full, and to come off of full quickly.
Anybody got any ideas, I'm at a loss? I guess I could throw $150 and a new sender at it and hope that fixes it,
The gauge itself appears to work fine. It points right at "F" right after I have filled the tank (though it comes off that mark very quickly - after about 20 miles). The gauge sweeps evenly all the way to empty and comes to a final rest just counter-clockwise of the "E" mark".
This is where is gets odd. When I refill my 24 gallon tank (well, that is what it is supposed to be) from when the gauge shows empty I can only put about 16 gallons back in. I have crudely measured the amount of fuel in the tank by dropping in a wooden dowel and find that there is about 1/3 of a tank remaining when the gauge read "E". I have put an ohm meter on the sender (while it is still in the tank) and see that it reads as it should (89 ohms at full, 51 ohms at half-ish and 0 at empty).
I thought that perhaps the float arm might have been bent, but can't conceive of a situation where bending it would cause it to show empty with a lot of gas in the tank, to read full when full, and to come off of full quickly.
Anybody got any ideas, I'm at a loss? I guess I could throw $150 and a new sender at it and hope that fixes it,
Last edited by StDomingos; May 5, 2017 at 06:11 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Sounds to me like it is working O.K. It goes to full when you fill it and it goes to empty when it's empty. What else do you need to know?
P.S. The only accurate info you need from a fuel gauge is when it is approaching EMPTY.
I know of NO C3 fuel tank that holds 24 gallons.
P.S. The only accurate info you need from a fuel gauge is when it is approaching EMPTY.
I know of NO C3 fuel tank that holds 24 gallons.
Last edited by 7T1vette; May 4, 2017 at 05:22 PM.
Instructor
Joined: Jan 2017
Posts: 150
Likes: 42
From: mountains of N.E. Georgia Georgia
I believe all Vettes after 78 had 24 gallon tanks. My 78 has a 24 gallon tank.
1978 Corvette Specifications
Dimensions
Wheelbase (in.) 98.0
Track Frt/Rear (in) 58.7 / 59.5
Length (in.) 185.2
Width (in.) 69.0
Height (in.) 47.9
Frontal Area (in) NA
Ground Clearance (in.) (minimum) 4.3 in.
Curb Weight (lbs) 3500
Coefficient of Drag NA
Weight Dist. F/R (%) 47.6 / 52.4
Coolant Capacity (qt.) 20.7
Fuel Capacity (gal.) 24.0
Oil Capacity (qt.) (w/ filter) 5.0
Info obtained at http://www.thevettenet.com/corvette_specs.php?year=1978
1978 Corvette Specifications
Dimensions
Wheelbase (in.) 98.0
Track Frt/Rear (in) 58.7 / 59.5
Length (in.) 185.2
Width (in.) 69.0
Height (in.) 47.9
Frontal Area (in) NA
Ground Clearance (in.) (minimum) 4.3 in.
Curb Weight (lbs) 3500
Coefficient of Drag NA
Weight Dist. F/R (%) 47.6 / 52.4
Coolant Capacity (qt.) 20.7
Fuel Capacity (gal.) 24.0
Oil Capacity (qt.) (w/ filter) 5.0
Info obtained at http://www.thevettenet.com/corvette_specs.php?year=1978
Instructor
Joined: Jan 2017
Posts: 150
Likes: 42
From: mountains of N.E. Georgia Georgia
I have a problem with the fuel gauge on my '81 and I can't find anyone else who has had a similar problem.
The gauge itself appears to work fine. It points right at "F" right after I have filled the tank (though it comes off that mark very quickly - after about 20 miles). The gauge sweeps evenly all the way to empty and comes to a final rest just counter-clockwise of the "E" mark".
This is where is gets odd. When I refill my 24 gallon tank (well, that is what it is supposed to be) from when the gauge shows empty I can only put about 16 gallons back in. I have crudely measured the amount of fuel in the tank by dropping in a wooden dowel and find that there is about 1/3 of a tank remaining when the gauge read "E". I have put an ohm meter on the sender (while it is still in the tank) and see that it reads as it should (89 ohms at full, 51 ohms at half-ish and 0 at empty).
I thought that perhaps the float arm might have been bent, but can conceive of a situation where bending it would cause it to show empty with a lot of gas in the tank, to read full when full, and to come off of full quickly.
Anybody got any ideas, I'm at a loss? I guess I could throw $150 and a new sender at it and hope that fixes it,
The gauge itself appears to work fine. It points right at "F" right after I have filled the tank (though it comes off that mark very quickly - after about 20 miles). The gauge sweeps evenly all the way to empty and comes to a final rest just counter-clockwise of the "E" mark".
This is where is gets odd. When I refill my 24 gallon tank (well, that is what it is supposed to be) from when the gauge shows empty I can only put about 16 gallons back in. I have crudely measured the amount of fuel in the tank by dropping in a wooden dowel and find that there is about 1/3 of a tank remaining when the gauge read "E". I have put an ohm meter on the sender (while it is still in the tank) and see that it reads as it should (89 ohms at full, 51 ohms at half-ish and 0 at empty).
I thought that perhaps the float arm might have been bent, but can conceive of a situation where bending it would cause it to show empty with a lot of gas in the tank, to read full when full, and to come off of full quickly.
Anybody got any ideas, I'm at a loss? I guess I could throw $150 and a new sender at it and hope that fixes it,
It's a C3 Vette so your problem is likely a bad ground or a vacuum leak! Sorry I couldn't be of any real help. Good Luck!
Team Owner
Joined: Jun 2001
Posts: 23,375
Likes: 1,066
From: Virginia USA
Sounds to me like it is working O.K. It goes to full when you fill it and it goes to empty when it's empty. What else do you need to know?
P.S. The only accurate info you need from a fuel gauge is when it is approaching EMPTY.
I know of NO C3 fuel tank that holds 24 gallons.
P.S. The only accurate info you need from a fuel gauge is when it is approaching EMPTY.
I know of NO C3 fuel tank that holds 24 gallons.
I'm sure Willcox can answer this. PM him.
Le Mans Master
Joined: Jul 2000
Posts: 6,664
Likes: 162
From: columbia city in
I believe all Vettes after 78 had 24 gallon tanks. My 78 has a 24 gallon tank.
1978 Corvette Specifications
Dimensions
Wheelbase (in.) 98.0
Track Frt/Rear (in) 58.7 / 59.5
Length (in.) 185.2
Width (in.) 69.0
Height (in.) 47.9
Frontal Area (in) NA
Ground Clearance (in.) (minimum) 4.3 in.
Curb Weight (lbs) 3500
Coefficient of Drag NA
Weight Dist. F/R (%) 47.6 / 52.4
Coolant Capacity (qt.) 20.7
Fuel Capacity (gal.) 24.0
Oil Capacity (qt.) (w/ filter) 5.0
Info obtained at http://www.thevettenet.com/corvette_specs.php?year=1978
1978 Corvette Specifications
Dimensions
Wheelbase (in.) 98.0
Track Frt/Rear (in) 58.7 / 59.5
Length (in.) 185.2
Width (in.) 69.0
Height (in.) 47.9
Frontal Area (in) NA
Ground Clearance (in.) (minimum) 4.3 in.
Curb Weight (lbs) 3500
Coefficient of Drag NA
Weight Dist. F/R (%) 47.6 / 52.4
Coolant Capacity (qt.) 20.7
Fuel Capacity (gal.) 24.0
Oil Capacity (qt.) (w/ filter) 5.0
Info obtained at http://www.thevettenet.com/corvette_specs.php?year=1978
my 82 has 24 gallon http://www.parts123.com/corvettecent...50g&ukey=17077
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
My '72 has grown to 23 gallone, I have DPFI on the 350 engine, so fuel slosh was an issue, so added a tank forward and under to cure that problem, my aftermarket gauge is not damped, and so bouncees all over the place when driving.....and yes, the gauge reads funky when in the garage....I can shine a light down the filler and see the float, and also I have a stick I have marked at full 10 gal, and so tank being symetrical, 1/2 that is 9 and 1/2 of that is 4.5 so hard, rocket science.....
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,209
Likes: 9,347
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
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My '72 has grown to 23 gallone, I have DPFI on the 350 engine, so fuel slosh was an issue, so added a tank forward and under to cure that problem, my aftermarket gauge is not damped, and so bouncees all over the place when driving.....and yes, the gauge reads funky when in the garage....I can shine a light down the filler and see the float, and also I have a stick I have marked at full 10 gal, and so tank being symetrical, 1/2 that is 9 and 1/2 of that is 4.5 so hard, rocket science.....
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Thread Starter
Instructor
Joined: Jun 2015
Posts: 178
Likes: 34
From: Calgary Alberta
I assure you all of you doubters that it is a 24 gallon tank.That is a good question. I have yet to find out because I have no idea how much fuel is in the tank after the gauge hits E. I suppose I could drive around with a Jerry can and wait and see.
What actually triggers the light? I would have thought it was based on a low ohms signal from the sender. If that is the case I think it would have come on by now. I can pull it out and bench test it as per the Willcox video and see.
Melting Slicks
Joined: May 2015
Posts: 2,365
Likes: 428
From: Cape Girardeau Missouri
Took the first drive after winter work and tested things to include fuel gauge/low fuel alert operation.
'79 L82 all stock except for true dual w/o cat.
After the "LOW FUEL" came on steady I drove 44 miles of mixed driving. The owners' manual says there are "about two gallons" of fuel when the light comes on.
In hilly terrain got 18 MPG mixed cruising with performance tests; 24 MPG steady cruising about 55 mph and 14 MPG city with frequent poorly timed lights.
'79 L82 all stock except for true dual w/o cat.
After the "LOW FUEL" came on steady I drove 44 miles of mixed driving. The owners' manual says there are "about two gallons" of fuel when the light comes on.
In hilly terrain got 18 MPG mixed cruising with performance tests; 24 MPG steady cruising about 55 mph and 14 MPG city with frequent poorly timed lights.