Fuel gauge intermittent

Boeing

Boeing

Member
I have been searching this forum for information on fuel the gauge.
I would appreciate some help in finding a solution to my fuel gauge problem.
I have a 1946 F1 with a V8- FH and last fall I had the fuel tank re built. This spring I noticed that my fuel gauge has become unreliable reading ¼ to ½ when the tank is full. I changed the sending unit and I still have the same problem. If I turn the key to ON the fuel gauge initially goes to full with the tank full. After a few minutes the gauge will read anywhere from ¼ to ½ full. I tried moving the wires on the back of the gauge with no change.

Last year I converted the electrical system to 12V including all new wiring harness and step down resistors on all gauges except amp meter. Fuel gauge worked fine then. Not sure where to look next. Thank you for your help.
 
JSeery, thank you for getting back to me. I still have the old sending unit but it was doing the same thing intermittent. So this leads me to believe that it may be the gauge...
 
It could well be a wiring issue. Is the wiring original or a new harness? Grounding at the gauge can also be a problem. Two suggestions, if the wiring problem is not obvious by inspection.

1. Make up a temporary jumper wire from the sending unit to the gauge to the sender and see if that works. That would tell you if there is a wiring issue between the sender and the gauge.

2. If no improvement try a ground wire from the gauge to a know good grounding point. Might even try a temporary jumper wire from a ground point on the sending unit to the ground at the battery.

It doesn't matter which you check first, the ground or the sender signal wire.
 
Is there a pin hole leak in the sending unit float?
Does it work properly when hooked up but removed from the tank?
Is the sending unit "grounded" ?
Try running a separate grounding wire from one of the sending unit screws to the frame.
 
19Fordy, I checked yesterday and can confirm that there are no pinholes in the float.
Like I said earlier it will work for a few minutes and then go to 1/4 or 1/2. I will do as JSeery suggested and run some jumper wires in order to eliminate wiring or ground issues and see what happens. Thank you for your reply.
 
I have had a 47 and my 48, i have run a straight wire from sending unit straight to the frame to get rid of fluxation of gauge. Also can pull unit and check with ohm meter to check range of ohm's thru to empty-full cycle.
 
Ken Crans said:
I have had a 47 and my 48, i have run a straight wire from sending unit straight to the frame to get rid of fluxation of gauge. Also can pull unit and check with ohm meter to check range of ohm's thru to empty-full cycle.
Click to expand...

If it's an original sending unit it doesn't have an ohms cycle! Doesn't work that way. If it's a modern repo, then yes.
 
I wouldn't attempt to run the gauge on 12 volts, Ford cautions against high voltage in the manual, and that's with a 6v system.
 
JSeery said:
I wouldn't attempt to run the gauge on 12 volts, Ford cautions against high voltage in the manual, and that's with a 6v system.
Click to expand...

Yes but

It's no longer a Ford as both voltage and sender are different.

I suggested removing the resistor as when the gauge reads 1/2 or 1/4 sounds like it could use a boost with something having a mid-life crisis. However, in re-reading I note the gauge spends some time (unspecified) at full before dropping to half or less. That change is troublesome and suggests the gauge has a problem after the heat in the bimetal strip stabilizes.

Also after re-reading it isn't clear that the new sender is Ford or resistance replacement sender. I hereby rescind my earlier recommendation without that knowledge.

BUT now I'm wondering about the ground of your new gas tank. A poor ground might make the gauge read ok at first then break down. Flying blind - can you provide a ground to the tank. Also not knowing your resistor situation can you wiggle the wires to it and the gauge as looseness could be a cause.
 
After this incomplete thread JSeery posted a pertinent 'How Ford Gauges Work'. A spate of other fuel gage problems also presented.

Boeing, I believe you can change just the single gauge. But I like Ford's gauge test which JSeery posted in his article and suggest you perform that (and apprise us the results).

Disconnect wiring to the Gauge Unit and connecting the gauge to a 1 ½ volt source (a “D” cell battery works well). The gauge should display mid-scale with a 1 ½ volt input and full-scale with 3 volt input (two “D” cell batteries).
 
Paul Thank you for getting back to me re the fuel gauge, sort for the delay.
I have checked the ground, run a new wire to the gauge and tried wiggling the wires to see if it made a difference. Nothing made any change. I will try the "D" cell and see what I get. I guess that the other option will be to replace the gauge only if I can locate one...
 
In your first post you stated that you changed the sending unit. Where did you get the second sending unit? Was it a used one or a NOS unit?
 
This spring I had the same problem with the original sending unit. " that being the gauge being erratic and unreliable". So I decided to replace the sending unit which I purchased from Joe's Antique Auto. Replaced the sending unit and I still have the same problem. This is why I think it is the gauge itself which is at fault. I was wondering if I could replace only the fuel gauge or do I need to replace the whole dash cluster? If the gauge is replaceable, where can I locate a fuel gauge? As I said before the ground is good, I tried a different wire from the sending unit to the gauge and tried to wiggle the wires behind the dash cluster to see if that would move the needle but no luck.
 
The gas gauge is replaceable in the gauge cluster. Not a particularly difficult task. I see gauges for sale on EBAY and here on the Ford Barn occasionally both NOS and used. Someone familiar with electrical theory in your local area should be able to help you diagnose your problem.
 
As old as these vehicles are, I would be wondering if you can confirm that what is mentioned as "the original" sending unit is in fact an original King Seeley unit. No photos so no way of knowing what is original and what's not.

The King Seeley system does not function quite the same as the modern replacement crap. Your only recourse is to go back with serviceable King Seeley components or change both components (indicator and sender) to modern type components. There are a lot of threads on this forum about problems with original systems and many have photos of the OEM senders.
 
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