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Fuel Gage Repair
I have a non functioning fuel gage on my ’55 Fireflite. I’ve checked the ground on my gage and sending unit, and also verified continuity on the sending unit wire. The prior owner converted to 12 volt and had installed a volt reducer on the gage, but the reducer was not working. I replaced the reducer, and the gage now “comes on,” but it stays on empty (or 1/4 tank-can’t really tell which).
I need to determine if it’s the sending unit, the gage, or both that need replacing. Burnbaum has both units in stock ($85 each), but electrical parts are not returnable. The manual says to use a spare (working) sending unit to determine which has gone bad, but I’d like to avoid getting stuck with a sending unit I don’t need. Is there a way to isolate my problem without buying either?
Also, if I do need to replace the sending unit, any advice on how do this without the special tool referenced in the manual? Opening up the gas tank makes me nervous!
Maybe check the float on your sending unit. It could possibly be stuck.
I have a similar situation on my '59 Firesweep where the dash gage shows the sign of life just above empty when the key is turned on but I know I have at least 1/2 tank of gas. My next move is the fuel sending unit in the tank and fortunately my tank unit is accessible from just above the differential and I don't have to remove the tank nor the trunk mat in which case mine is the factory original and appears to be be very brittle. I checked the wires at the tank and all are properly connected so I might as well remove the float unit and check it out. Hopefully I'll find the culprit and either be able to get the unit working or order a new sending unit and install it.
I'll Probably do this in a few weeks and will keep you posted.
"It's delightful, it's delovely, it's DeSoto"
Thanks Fred. I’m going to try testing the sending unit in the tank using a procedure found in my shop manual. Using a six volt battery, I should (theorically) be able to see a Mili-amp change on my tester between a full and empty tank from the disconnected sender, IF the sending unit is working. Currently just running the tank down! My access is under the trunk mat, but -assuming the unit fails- I’m wondering how to get it out/off the tank. Is there a tool openly available for this?
No special tool is needed. Just a hammer and a flat blade screwdriver is all. You'll just need to loosen the retaining ring and then remove it and the sending unit will come out.
"It's delightful, it's delovely, it's DeSoto"
I tried the (off tank) sending unit test procedure on the tank but it didn’t work, so I removed the sending unit and tried it on the bench. The float arm worked fine, and sure enough, the miliamp output on my tester increased as the float was raised to the full position. So, the manual says this test confirms the sending unit is working, but cannot confirm that its calibration is correct. Since my gage continues to register in the quarter tank position no matter what -and I tried spinning the sending unit around different clock positions on the tank- according to the manual I can assume the problem is the gage.
Anyone out there concur?
P.S. Not sure what the float is made of, but it has a cork-like texture. Is it possible the float has lost its buoyancy?
@rogerhubbs Those original tank gauges had cork floats, usually coated in something impervious to fuel (from that era) so they did absorb liquid and remained buoyant. Could be time has taken its toll or the new ethanol-concocted fuels have removed the coating. Seems like new replacement tank floats use a rubber/composite material for the float.
My fuel gage is working again! Repair was twofold:
As mentioned previously, I had to replace the gage voltage reducer the previous owner had installed as part of the conversion to 12 volt. I also replaced the reducer on my temperature gage which brought it back to life as well. These reducers seem prone to failure, and I believe should be checked for output before checking anything else when a gage is not functioning. An irony to 12 volt conversions; needing to convert your gage supply back to 6 volt!
The tank unit was the other piece of my puzzle. I got the original sending unit working again off the car with some electrical cleaner, but it would only register 3/4 full on the gage (with a full tank), even after several attempts to recalibrate by bending the float arm.
So I purchased a new unit from Bernbaum’s, which worked, but it was wicking fuel vapor up through the unit’s two screws/bolts which hold it together. Bernbaum sent me a replacement, but it did the same thing. So I applied Steel Epoxy Filler (suitable for gas tank repairs) around the screws/nuts on both sides of the unit, and that seems to have sealed it up.
So, assuming the unit works as well with an empty tank and in between, success!