1939 Ford Deluxe Fuel Sending Unit Question

J

jstrez5

Senior Member
I will be putting in new send unit to my 1939 ford deluxe. I already emptied the fuel from the tank, and removed the old sending unit. It was corroded with rust and the float had gas leaking out when I removed it from the tank. I ordered a new sending unit from eclassics. I have the original gauges on my dash, eclassics claims their sending unit will work with the original gauges in the car. My question is how much gas needs to go back in to the tank and how would I test for a true reading on the gas gauge?

As always any help is greatly appreciated.


Jim
 
Before installing in the tank, I would connect the wire and ground the sender. Have a friend watch the needle as you SLOWLY lift the float arm and watch for movement on the gauge. You can get a pretty good idea how it's going to respond before you go to all the trouble and mess of checking it with fuel in the tank.
 
Good advice above about adjusting the float arm before installing. You can measure the depth of your tank and draw a cross-section template on the garage floor. Then lay the sender over the template and adjust the arm so the arm rests on its limit on the sender just before the float would bottom-out on tank floor and tank roof. If you can't get both, tank floor is more important.

All the aftermarket senders work on the modern resistance principal, totally different than the original sender's pulse principal. The gauge needle will move, but you will never be able to get the gauge to read accurately over the full scale. After much trial-and-error with added resistors, I was able to get my gauge accurate near empty tank. Remains grossly inaccurate when lots of gas in the tank. Never heard of a way around this with any aftermarket sender.
 
I was curious and looked at the website— it is a resistance sender - perhaps “works” means it bolts in and can make the needle move.
 
I've always wondered why these guys would go to all the trouble to make something that will bolt in, have the correct mechanical components, and then use the wrong electrical operating principle.:confused:

If I had the money and time, I'd try to convince my EE buddy design a microchip with the King-Sealy logic connected to some kind of pressure sensor that would be suitable to be used in place of the original Ford sending units. I'll bet one could be designed to work with fuel, temperature and oil pressure senders.
 
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jstrez Post a picture of what your original gauge looks like. I salvaged a rusty King-Sealy for my '46 Coupe, and it sure works better than the aftermarket that was in the car when I bought it. Unless there is a rust hole in the body of the sender, it is very likely that it can be salvaged, and even then, unless there is damage to the internal components, the hole could be soldered over. for my rebuild, I blasted the housing with walnut shells, and used a new float and float arm to repair the existing arm. The arm needs to be "profiled" (bent) to match the size/shape of your tank. See pictures.
 

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The moral of this story is : DO NOT discard an original Ford sending unit just because it doesn't work.

They can usually be repaired.
 
tubman makes a great point about developing a sending unit that would work accurately. If you have the patience and persistance you can get the old KS gas tank sending unit to work, unless you damage the internal windings or the carbon resistor.
Is the market large enough? A Forum SEARCH on 'Gas Tank Sending Unit" will provide tons of info.
 
The new unit will be correct at one point on your original gauge , if your lucky .
Like a broken watch thats correct twice a day
 
Sorry to hear you discarded the original.
If there is a salvage yard near you -- go and look for a 1/2 ton (early 50's) Ford truck. Most have the gas tank behind the seat.
Check to see if the gas tank sender is there. If so, remove the tool tray and remove the sender.
Most times (like 95%) the sender is good and all you will have to do is un-snap the float rod connector and install the one from the original, or a replacement. Over the years when one of my senders quit, that's what I did.
 
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