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Discussion Starter #1
The fuel gauge in my 68 Galaxie stopped working. Well, it does move a tiny bit on startup but just moves from a little below "E" to right on "E" even thought the tank is full.

I'm wanting to trouble shoot. Thinking first about checking the sending unit. Is it possible to jump the fuel sending unit connector (to see if the gauge will move) by inserting a wire loop in the connector or would that be too much current for the gauge?

Is there a common failure point (like is it common for the actual gauge in the dash to fail)?

Thanks!
 

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you should be able to short the sender wire to ground at the tank and the gauge should go full-scale and show "Full".
If this works, you know where the issue is (in the tank...)
 

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Jiffy's got the right place to start. Also:

Do the other gauges (temp, oil pressure) work correctly? If not you might have a problem with the constant voltage regulator which provides a steady voltage to the gauges.

Sending units are a common failure point. The floats often leak and fill up with fuel so they don't float any more. You can get a new float from any number of Ford parts sources like autokrafters. The sender may also have an electrical problem. These are variable resistors with a mechanical sliding mechanism. They wear out over time.

- John
 

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Discussion Starter #4
Thanks for the tips. Going to try Jiffy's test first since getting into the dash to check the voltage regulator is a huge pain in the neck. But to clarify, my sending unit has two prongs on it. I assume one is power and the other ground. The connector has two wires. So would just making a U-shaped wire loop and shorting out the two wires in the connector do the trick to determine if the problem is in the sending unit or the gauge itself?

I replaced the gas tank a year ago and got a new sending unit. But when I went to connect the old connector to the new sending unit I discovered that the old connector harness was cardiod shaped and the new sending unit was round. So I couldn't get the old connector on to the new sending unit. Anyone else discovered this problem? A frustration (putting it mildly) for sure.
 

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sounds like a sending unit for an older car. 63-4 used bullet connectors, i think all newer use spade connectors. if grounding the sender doesn't make the gauge go full, the cvr could be a problem, but if the temp gauge works- the cvr works
 

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My '63 in-tank sending unit only has one wire, dunno why you've have two? Unless an EMPTY warning indicator was an option. Not heard of a sending unit not being grounded through the tank.

BUT

Ignore how many connectors you have on the tank. How many wires do you have on the harness going back to the gauge cluster? I'm thinking there is only 1 so - ground that wire. See if the gauge goes to full.

If it does, then the issue is in the tank and is likely to be the sender or the float. If so, empty the tank, remove the locking ring and remove the sender unit. Check what the eternal connectors to go, measure it's operation with a multi-meter and figure out what the connecters do and if you are in need of an external earth or are using the wrong connecter on the sender.
 

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Jiffy was right on with his troubleshooting suggestions. Another consideration, I know the 68 has a version of the sender that incorporates a low fuel light and the other version if you have a car without a low fuel light. I am not electrically inclined, but from my reading, know the way it measures the gas is related to the float and how many ohms are sent back from the sending unit to the gauge. If you have the wrong sending unit in the car, such as a low fuel light sender in a non low fuel light car, the reading may be off.

How much off, I honestly dont know that, but it would make a difference, at what part of the range of the gauge, maybe someone here with better electrical knowledge can educate us all on that.
 
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