[NA] Truck Fuel Gauge [NA]

Greg Bockelman

Greg Bockelman

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Greg Bockelman
I have a '56 Ford pickup in which the fuel gauge reads full all the time. I can take the lead off of the fuel sender at the tank and the gauge will drop to empty. When I touch the lead to ground, it will go back to full. That is all the troubleshooting I have done.

Any ideas what else I can do to troubleshoot? How can I tell if it is the sender or the gauge?
 
Sounds like a short in the wire going to the gauge.

Let me take it to my shop and I can get it fixed for ya in a year or two....
 
Its a very simple system, you've already troubleshot enough, but if you have a variable resistor, or a couple resistors of different resistance, laying around, try it between the lead and ground.
 
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Zeldman said:
Sounds like a short in the wire going to the gauge.
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I think if the wire from the gauge was shorted to ground, the gauge would stay on Full when the wire was lifted from the sending unit. Sounds to me like the gauge is working properly, but the sending unit is bad. You could verify it with an ohm meter.
 
SDB said:
I think if the wire from the gauge was shorted to ground, the gauge would stay on Full when the wire was lifted from the sending unit. Sounds to me like the gauge is working properly, but the sending unit is bad. You could verify it with an ohm meter.
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Yes, the gauge works, its accuracy is yet to be determined. If he can find resistance info on the sending unit, he should be able to get a few resistors and check accuracy.
 
Dana said:
Yup, a short in the sending unit in the tank.
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Exactly. The cause of the short could be as simple as a stuck float, but the problem is with the sending unit, not the gauge or the wiring.
 
My old Lotus used to have the same problem. Turns out the float arm had seized in the up position.
 
My bet is that the float is stuck at the top of the tank. Had an old F250 with that problem. It's like a toilet float - simple arm with a float on top. It floats where the fuel is.

Unless it seizes. Then it always reads the same. Disconnecting the power moves it to 0 because the power is disrupted. Putting power back on reads correctly where the float is positioned.

If the tank is similar (and I bet it is) you can actually remove the assembly without removing the tank. Clean it up or replace the float as necessary.
 
Replace it with a Cessna fuel gauge. At least it'll read right twice...
 
Greg Bockelman said:
LOL. Well, the truck is in the States and I do come and visit now and then.
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I don't fully trust the fuel gauge in the 17 year old Subaru. I just reset the trip mileage but could be done with a regular odometer and a notepad too. :)
 
Well, as it turns out, the fuel sender was bad. To make troubleshooting difficult, I found out the new style senders don't work with old style gauges and vica versa. My brother happened to have an old style sender and it worked. All is well in my truck world again.
 
Greg Bockelman said:
Well, as it turns out, the fuel sender was bad. To make troubleshooting difficult, I found out the new style senders don't work with old style gauges and vica versa. My brother happened to have an old style sender and it worked. All is well in my truck world again.
Click to expand...

Your brother has excellent taste in spare parts that he keeps lying around. Haha.
 
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