Please help. I would like to get my stock fuel tank back in, however, the sending unit is pretty bad off, its rusty and half eaten through. The weird thing is that it still works my guage. I would like to get a new sender but the I dont know what the resistance reading should be on a 50 Ford product sender. I am bouncing from 90 to 230 to 0 to 570 ohms, its just not stable. Long story short, does anyone know what the ohm reading should be so I can get the correct sender. Thanks in advance: Steve
50 Lincoln and Merc gas tank sending units work on an entirely different "non-linear) (linear) principle than the common "ohms" units. it would seem logical that the 49-51 merc gas tank sending units and the 49-51 Lincoln gas tank sending units are the same. They also work on the same principle as the 1940's and 50's Ford car units. The part number for the 1949-51 Mercury Station Wagon fuel tank sending unit is 01A-9275-A. The part # for the 49-51 p***. car fuel tank sending unit is: 99A-9275-B. Your best bet is to install another used or new OEM unit. Be sure and read all this and you will see why. http://www.fordbarn.com/forum/showthread.php?t=64991&highlight=gas+tank+sending+unit and all of this: http://www.fordbarn.com/forum/showthread.php?t=40850&highlight=gas+tank+sending+unit In your leisure time you will also want to digest the material provided in all these: http://www.fordbarn.com/forum/search.php?searchid=1836730&pp=25 Here's how your gas tank sending unit and fuel gauge work together. They both work on the bi-metallic non-linear principle. Click once on pictorial to enlarge and then click on pictorial again to really make it big. The same is true for the next batch of posted pics.
More info. These pictorials were taken from the 49-51 Mercury Manual. there may be a few cases where the aftermarket fuel tank sending units claim to work properly, but they are few and far between from what I have read. Some may "work", but they do not "work" accurately. the key word is "accurately". For the last year or so there has been the same OEM 49-51 Merc gas tank sending unit for sale on ebay for over $300, but that is an absurd amount. Get a used one and give it a try. Hope this helps.
You can use a brake adjusting tool or a large bladed straight blade screwdriver to gently pry the top off your sending usnit and it will look like the 1940 ford gas tank sending unit shown below as they both operate on the same non-linear bi-metallic strip principle. Notice that the part # is the same as the 1949-51 Mercury station wagon. Also there is a genuine old time color coded carbon resistor. I wonder if it would be possible to determine the ohms value of that carbon resistor and then replace it with a modern style resistor? Of course the ideal would be if someone could develop a modern gas tank sending unit that would duplicate the original AND work in conjunction with the original fuel guage so as to give an ACCURATE reading of fuel level at the full, 3/4, 1/2. 1/4 and E levels of fuel in the tank.Wish I knew more about electronics. I'd give it a try. The Lincoln gas tank capacity is 21 1/2 gallons and the Mercury is 19 1/2 gallons. So, I bet the only difference in the fuel tank sending unit is the length of the float arm and/or the value of the carbon resistor. Let us know what you find out. All the best, Jim
My gauge works great until it gets to 1/2 a tank then stops. Needless to say I buy gas as soon as it gets close. I put 7 or 8 gals in it and the gauge goes to full. Would like to replace it or see if it's just stuck. Car set for many years and must have had 1/2 a tank of gas in it.
It may already have a replacement sender in there. See if it compares to the pictures already posted to be for certain. The original current based systems were very reliable and more accurate than most new cars are. It's a shame that some company doesn't reproduce them as King-Seeley originaly made them for FoMoCo.
Interesting stuff. Since I have a 53 Merc and a 54 Lincoln, I am going to explore the mechanisms and signals. It looks to be fairly straightforward to build a converter that will take a simple ohm type sender and convert it to output the proper signals for the bi-metal gauges. Seems that the temp and oil gauges are very similar, and the senders are probably similar too.
looks like i was wrong. i have used a 75-10 ohm sender with a `40 and `49 ford fuel gauges successfully , so i ***umed it would be the same
Variable resistance works in a similar fashion to the the old Ford variable current systems but it would take a variable resitor with a very wide band of operation to make it work correctly. The little brush on the variable resistors usually wears out quicker than the points or the heated bi-metalic switch arm of the variable current device. I've resurected quite a few old King Seeley sending units by just cleaning them up. The temperature and pressure senders are sealed so you can't do anything with them when they are gone but they last a long time. Many of them outlasted the cars they were in for sure.
Wow, thats alot of info. Hey, 19fordy, the pics you sent were *****en, my sender looks identical to the one in the pics. I am going to clean mine up and see if I can uncover the part #. My bet is that its the same basically now I have a more wide range of options to choose from. Thanks guys!!
I know I'm dredging up an old forum, but I must say, great info shared. I was running across the same issues here. My car was stripped of all old cloth wiring, and has slowly been retired, as well as converted to 12 v. No longer has the y block, has a 351 Cleveland in it now. I purchased this 12v to 6v Reducer to get the correct vital get o the gausges. https://www.ebay.com/itm/12-volt-to...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649 Took out the original sender, everything looked ok, so reinstalled. Fuel gauge is now registering. I haven't driven it far enough to see if it will drop down to empty yet. Now I have another problem though, and that's with the oil pressure sending unit. I purchased this one, thinking I had the right one. But it barley makes the oil gauge move. I also have a mechanical unit, which shows about 65 psi at start up, so I know I have pressure. Does anyone know the correct oil pressure sending unit to make my oil gauge work properly? They had 4 different listings for different years, but the part number was the same on all (41a-9278). https://www.ebay.com/itm/48-49-50-5...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
Searching for the answer on this exact question.. Shoe Box Central sells a brand new fuel sender replacements and they are listed as 73-10 ohms for anyone else searching. I'm running an aftermarket early Mustang type tank from Tanks Inc and they make the correct ohm sender.
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