| fuel gauge pegged to beyond full [message #363941] |
Tue, 11 May 2021 08:47  |
ktcnyc
Messages: 25
Registered: September 2020
Karma: -1
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Junior Member |
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Hello - I recently had my gas tanks dropped and all lines and 2 senders replaced. All was well for a while until the dash gas gauge suddenly pegged to beyond full and stays there. What is going on ? Where do I start to hunt down the problem? Many thanks for any guidance.
KC
Kevin Cloutier -'77 Eleganza II-455, 6 disk brakes, Edelbrock carb, headers, , resident of NYC and Dingmans Ferry, Pa.
'72 MGB-GT & '73 MGB convertible
Member GMCMI since 8/20
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| Re: fuel gauge pegged to beyond full [message #363944 is a reply to message #363941] |
Tue, 11 May 2021 10:10  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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ktcnyc wrote on Tue, 11 May 2021 09:47Hello - I recently had my gas tanks dropped and all lines and 2 senders replaced. All was well for a while until the dash gas gauge suddenly pegged to beyond full and stays there. What is going on ? Where do I start to hunt down the problem? Many thanks for any guidance.
KC
Kevin,
On GM gauges of that period, full is an open circuit.
If it is pegged on both tanks, it could be in the dash. But, there is an immediate place I would go. Both gauge leads go to a connector down by the selector valve. It is a three wire connector and one goes to the selector valve. The other two go to level senders.
You wrote "had my gas tanks dropped"...
There is a reasonable chance the person that did this did not get the connector referred to above reconnected properly. Think about that as you proceed.
Ground one of those to the frame and see if the instrument reports empty for one tank.
- If yes, the problem is not in the dashboard.
- Neither go to empty, your problem is somewhere above. The switch can be a problem. but that is not a real common failure. The switch can be disassembled and cleaned.
If you have a meter handy. Measure the resistance of either tank sender at the connector. It should be 90ohms or less.
If it reads way over 90, move the other probe from the frame to the tank itself. If you get 90 or less now, figure a way to ground the tanks to the frame.
This last is a very common issue and has been will most vehicles for a long time until in-tank pumps forced manufacturers to include a good ground.
Let us know what you find.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: fuel gauge pegged to beyond full [message #364006 is a reply to message #363944] |
Fri, 14 May 2021 18:10 |
ktcnyc
Messages: 25
Registered: September 2020
Karma: -1
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Junior Member |
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Hello Matt, Turns out the fuel gauge works when switched to the reserve tank. I removed and cleaned the switch anyway - to no improvement.
"Both gauge leads go to a connector down by the selector valve" - where exactly is this located? Any other suggestions considering that the gauge works for one tank?
Many thanks, Kevin
Kevin Cloutier -'77 Eleganza II-455, 6 disk brakes, Edelbrock carb, headers, , resident of NYC and Dingmans Ferry, Pa.
'72 MGB-GT & '73 MGB convertible
Member GMCMI since 8/20
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| Re: fuel gauge pegged to beyond full [message #364008 is a reply to message #364006] |
Fri, 14 May 2021 20:08 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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ktcnyc wrote on Fri, 14 May 2021 19:10Hello Matt, Turns out the fuel gauge works when switched to the reserve tank. I removed and cleaned the switch anyway - to no improvement.
"Both gauge leads go to a connector down by the selector valve" - where exactly is this located? Any other suggestions considering that the gauge works for one tank?
Many thanks, Kevin
Kevin,
It has been years since I had to find one, but the simple answer is:
Get underneath (with the coach blocked up) and find the selector valve. That is a not large device the two fuel line coming from the tanks and one going forward. It will have one wire connected to it. Follow that wire and it will lead you to the connector you need to find. You can do tests at that connector to establish which way you go from here.
If you ground both and both tanks report empty, then you know the problem is toward the tanks.
Did you try grounding the subject tank??
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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