'41 P-U Fuel Gauge Reads Too High
 

When the gauge reads 1/2 the tank is almost empty. Where should I start
the troubleshooting? I suspect the float/sending unit. Truck is stock 6V.

Re: '41 P-U Fuel Gauge Reads Too High
 

I have the same problem.. but mine goes empty at a 1/4 tank.. I am guessing I either did not cut the length of the float rod short enough.. or my electrical guy did not get the ohm resistance within specs..

Re: '41 P-U Fuel Gauge Reads Too High
 

could also be the fuel gauge, when did this problem start? lately or has it done this before, have you changed any thing? a little history of the problem would help

Re: '41 P-U Fuel Gauge Reads Too High
 

You make have a hairline crack in the brass sending unit float. Remove and solder it for best results. While you have the sending unit out keep it hooked up and move the flow up and down slowly to check the gauge reading. Don't do any soldering near the gas tank.

Re: '41 P-U Fuel Gauge Reads Too High
 

Hmmm...If the float has a hairline crack, then the fuel leaked inside would make the float sink lower...making the gauge read MORE empty than reality?

Re: '41 P-U Fuel Gauge Reads Too High
 

Are you using the original sending unit or an aftermarket one?

Re: '41 P-U Fuel Gauge Reads Too High
 

This sounds like an aftermarket sender for sure. The original sender and gauge are current/pulse devices. The aftermarket senders are an ohms/resistance device. They are really not 100% compatible with the original gauges, but some folks seem to get them to work and some do not. There are places that repair the original senders.

Re: '41 P-U Fuel Gauge Reads Too High
 

Thanks, guys! I will contact the seller for more info. on this problem. Might give us a clue on how to fix.

Re: '41 P-U Fuel Gauge Reads Too High
 

Good luck with that! :)

Re: '41 P-U Fuel Gauge Reads Too High
 

If the sender checks out OK The 36 fuel gauge has 2 adjustments..There
are 2 holes in the rear with arms that have small gear like slots on the
bottom at the hole. One controls the upper limit and the other the empty
position. It will take very little movement to make a change. G.M.

Re: '41 P-U Fuel Gauge Reads Too High
 

These questions come up all the time and are generally related to the difference between the old King Seeley current regulated system and the later ohm based rheostat variable voltage type sending units. Many folks claim they can make them work but the range will always be off no matter how hard you try to make it work. I think most folks shoot for a correct empty reading since you can't get all the way to both empty and full reading accuracy with a mix of technologies.

All I can suggest is to find a way to change the gauge to an ohmic value system, find a usable King Seeley sending unit or gauge unit, or live with the inaccuracy.

Re: '41 P-U Fuel Gauge Reads Too High
 

Totally agree. Find an old King Seeley sending unit as they almost always work. People like to throw them away so they can get a "new one" when working on the fuel system. Problem is new ones will never work correctly with the original gauge. The part that does go bad is the brass float as stated above. Here you can solder up the cracks, or get a new float.
Just my opinion

Re: '41 P-U Fuel Gauge Reads Too High
 

Words of wisdom IMHO.

Re: '41 P-U Fuel Gauge Reads Too High
 

I soldered cracks in my 47 merc sending unit,and tested it for leaks in a bowl of hot water to see if I sealed all the leaks,that will bubble in the hot water.After eliminating all leaks,I installed it back in the tank.I found out later that the float will ride higher in the water than it will in gasoline.With the extra weight of the solder,I'm not sure how well it will work.Another option is to cut the rod holding the float,and,cut the rod from an aftermarket assembly,then weld together maintaining overall length,and minimum overlap at weld,or butt weld to minimize any weight difference in the rod.

Re: '41 P-U Fuel Gauge Reads Too High
 

UPDATE...I contacted the prior owner. As part of the restoration he installed a new fuel tank and threw the old sending unit away with the old tank. Well, now I know...

Re: '41 P-U Fuel Gauge Reads Too High
 

Unfortunately that is so often the case. I am betting that the one he threw away was in perfect working condition, except maybe the float. The other problem is many people try to test the old ones with an VOM and look for variable resistance in ohms. When they cannot get a reading they decide it is no good. You can see this at swap meets. Keep in mind that a VOM will not test a King Seeley anything. If anyone has an old tank with the sender still attached, remove and keep the sender no matter what you decide to do with old tank. Carefully (they get damaged when the long rod gets all bent up ) store the sender and use it or give it to someone who needs it. There is no new substitute that will work. I bet that 80 to 90% of all the old ones out there are perfectly good.
My opinion

Re: '41 P-U Fuel Gauge Reads Too High
 

Most of the KS sending units were a lot alike. Cars with similar size and shape tanks could use the same sender. The 99A-9275-B sending unit was used from 1939 through 48 on Mercury cars, 1941 thru 1948 for Ford cars, and 42 thru 47 on commercial pickups so there should still be a few good ones out there. The major problem is that the new style "replacement" variable voltage type units are also listed under this number so it makes it more difficult to find one.

It is always a help to at least know what they fit when you are looking for an original.