I bought new fuel tank, sending unit and 12-volt to 6-volt reducer (have changed over to 12 volts but still have 6 volt gauges) for my 1954 ford. I made sure dash gauge was working then installed volt reducer. Bought sending unit from Midfity that matches oms for stock gauge. Hooked it up and before I installed in tank moved float arm and it registered perfect. Dropped sending unit in tank about 1/2 full of fuel and gauge would not move. Took out moved gauge worked great. Reinstalled same thing gauge didn't move. Checked all grounds and even ran an extra one and still nothing. Any help would be greatly appreciated. Thanks

 

Ford was still using King-Seeley senders and gauges in 54. These DO NOT WORK on an OHM/Resistance Model, but are King-Seeley Distometers that work on a completely different principle.

You state that the sending unit you bought from MidFifty had an Ohm rating - probably around 33 to 240 Ohms (probably part number 2697) . As such, it will not work with the stock King-Seeley Distometer type gauges. It is best paired with MidFifty's stock looking, but F-33 to E-240 Ohm range gauges (Part Number 2694-5355)

You won't have a good time mismatching king-Seeley and ohm/resistance equipment. For those having issues with your stock fuel gauges and new tanks/sending units, it's most probable that are two different "languages" being spoken. Most modern fuel gauges and senders are simply paired ohm meters and variable resistors; the gauge measures the resistance of the sending unit circuit which changes with the fuel level. However, our stock Ford truck sending units and gauges used a different language with King-Seeley equipment. These sending units supply a full voltage (6V, except for 56, in which 12V) through a heater wire in the gauge in the form of a square wave with the duration of the "on" being the variable determining the gauge reading. The longer the duration, the more fuel in the tank. It is this full voltage of current which heats the bi-metallic strip in the stock gauge that causes the gauge to read via a small gear train. Most (if not all) after market sending units are simply a variable resistor which sends a constant closed circuit of varying resistance to the gauge. Therefore, the sending units signal doesn't heat the bimetallic strip in the gauge as much making the calibration of the after-market sending units and the stock gauges nearly impossible to match up very well due to the differences in the principle of the signal.

Modern gauges are easy to pair as long as the sending units full and empty ohm readings match that of the modern gauge. Some senders and gauges are even highly adjustable in this regard, or 3rd party inline adjusters can be had.

For accurate readings, one cannot mix and match ohm/resistance based equipment with King-Seeley equipment. Your sending unit and gauge must match, either both must be stock type (King Seeley), or modern after market (with compatible ohm ranges). To accomplish this in your situation, is you can go back to your original sending style unit and gauge (with added voltage reducer), or replace your stock gauge with a gauge that matched your new sending unit.

 

I'm wondering if the float is rubbing against a baffle.

 

Below your original post bmoran4 gives the best explanation of the aftermarket vs stock gauge system components I think I have ever read. He should copy,paste, and re-use it everytime this question comes up.

As far as your situation. Could you please share with us the exact part number of the sender Mid-Fifty sent you so we can be sure were are talking whether it is a stock style, original type sender or the newer style that should only be pared with their newer stock looking, but 12 volt fuel gauge.

Thank You and Merry Christmas!

 

I have had the same issue you are having. Except mine was on a 56 12v system. I changed my in cab fuel tank to a C@3^y tank and sending unit out of a 70ish van, new of course. Silly me thought since this was a very documented replacement tank there certainly would be someone that got their stock gauge to work. Nope, I found no one that had accomplished this task. So, I bought two different ohms adjusters both worked perfectly out of the truck but NADA once installed. My solution was to have a gauge repair company install a C@3^y gauge in my original 56 gauge housing.
Since MidFifty is shutting their doors it might not help to get their part number since they made it up in their catalog and without knowing the manufacturer that may just be another rabbit hole.

 

Merry Christmas BJ!

The reason I am asking for the part number of the sender he ordered and received was I was going to look at the Mid-Fifty catalog and see which one he got so we know if it should work in his set up or not. I am thinking one way or the other he might of gotten the wrong sender.

Also he said he added a ground. Hopefully he grounded a screw on the senders' mounting flange
and has his cab grounded as well. All major ground points, battery, frame, and cab firewall grounded together at one good and clean reference point such as the engine block.

 

He's gotten practice because he typically answers this question 1-3 times per month every year.

This information has been floating around on this forum for years, but was never quite as "refined" as Moran puts it.

 

I just went through this, this year. I ended up replacing the gauge with the reproduction unit from MidFifty. Nothing else worked.
They currently list them in stock, but as they say: "once they're gone, they're gone." 1953-55 Ford F-100 Fuel Gauge, 53-55 Stars (midfifty.com)



Reproduction Fuel Gauge and Batt Gauge look-alike voltmeter


On a side note: in my case the King-Sealy gauge caused the resistance winding in the sending unit to melt the plastic. Call me crazy, but I found a tiny wire getting hot enough to melt plastic INSIDE my gas tank a little unnerving. That's how model rocket igniters work.


Ebay sending unit advertised as "for original type gauge" after failure

 

Gonna ask a dumb question here. The guy said his unit worked perfectly out of the tank when he hooked it up with the gauge in the dash and tested it. Then explain to me how it doesn't work at all when the only variable that changed is the float is being moved by the buoyancy a pool of gasoline instead of his hand. Could it just simply be the float "hinge" is too stiff to move in the liquid? He even put an extra ground on it.

 

That's a good point.

 

Did you buy the Mid Fifty sender with the part number of 1607-3555 ? If so that should be the correct sender to work with your stock fuel gauge. If that is not what you have then I believe you have the wrong unit.
If the sender is the correct one and it is still is not working in your tank, as mentioned before let's double check your ground wire to the sender flange on your tank.

 

Well Hooler 1 has a good point. I say it's ground too. I know my system is nothing like yours. A converted from 6 volt positive ground to 12 negative ground. Completely different animals. If it's doing what you say it's doing. That new tank is it a Taiwan pop off. Mine had a clear coatIng on the out side. But It was sent to the radiator shop and coated the inside for me. I stripped the area because you have to install an adapter. With a Taiwan tank don't recall but the stock is five screw and the Taiwan is six screw. The baffle should not be an issue provided your float goes towards the rear. I measured the tank depth then cut and adjusted my float and rod to be about one inch from the bottom and not touch and part of the metal tank. It's a metal float. One thing I did was silver soldier the float east west left right, not up down. Just what I did,it works. Suppose it's not that accurate, but it's in the ball park. Enjoy the holidays AJ

 

If it were me, I'd work up some extensions on the wires so I could hook up power to the sender while it's out of the tank, raise the float to the full position and make sure the gauge is on full, they try to work the sender into position and see what happens. I have to wonder if the float isn't floating, or some other issue is going on inside the tank for it not to read correctly when installed, but working fine outside. That's a head scratcher for sure. Is the float rod set correctly? Long enough and going through it's full motion?

 

Good point Wayne. The brass float could have a pinhole and has taken in gas and doesn't float anymore.

 

I started thinking about that earlier this morning too. I thought he probably got a new float with the sender, but that was just my assumption. Then again "NEW" now days is an acronym for Never Ever Worked. This also happened with my '56 when I first bought it. The gauge did not work either. It turned out to be 2 problems, the float with pins holes and the missing tank ground.