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Old 06-14-2018, 08:39 AM
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Default 1976 Commercial Chassis Fuel Sending Unit

For as long as I have known my 1976 Cadillac Superior Ambulance, the gas gauge has read full. To prevent any embarrassment, I watch the trip odometer. My summer project is to repair the gas gauge. I assured the sending unit has a solid chassis ground. I disassembled the rear license plate mount to access the brown gauge wire and when I touched it to the frame, the gauge dropped to empty - leading me to believe the gauge and wiring are intact.

My suspect is therefore the sending unit which I have been unable to source because the parts houses state “except commercial chassis”.

I purchased the 1976 Cadillac Shop Manual. Throughout the manual it will state “except commercial chassis” - however - I do not see where manual section 8 states there is any difference between a non-EFI standard auto sending unit and a commercial chassis sending unit.

Has anyone had success installing a “standard” unit in a 1974 - 1976 commercial chassis?
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Old 06-14-2018, 10:02 AM
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the problem is return hoses and vapor lines. then there is some debate as to what tank they used. it may not be a a Caddy tank. Dave up in Canada has some interesting takes on it. capacity would be your indication. i have been lead to believe the tank was smaller then the standard car. most likely your best bet is one of the universal ones. get a stainless steel one or it will get ate up.

as you have all ready preformed the test and determine the sending unit is bad. the next step is to do the visual and see if lines come out of the unit or some were else on the tank. and compare what you see with pictures. rockauto.com is one good place to get a look at pictures of parts. it might be just a case of plugging off lines you don't need. let us know what you find out
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Old 06-15-2018, 01:54 PM
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Default t 1976 Commercial Chassis Fuel Sending Unit

Do not if this place is any good , but one place that can rebuild it.

https://www.clocksandgauges.com/gas-...it-repair.html
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Old 06-17-2018, 11:07 PM
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These guys also:https://www.bobsspeedometer.com/1/120/index.asp

Family owned company, I personally have dealt with them since 1969.

One thing also. Is the gauge reading "full" or over past full? If past full it might be an open circuit condition in the wiring to the sending unit. Worth checking or running a new wire between a known good point on the harness to the sending unit.
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