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Do I need to replace 1955 fuel sending unit?

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  • Do I need to replace 1955 fuel sending unit?

    I'm wondering if I'll need to replace the fuel sending unit that's in my '55 truck, now that I've changed the fuel gauge to the 12v version. It's just a variable resistor in that sending unit, but can it handle 12v, since the one that's in there was part of a 6v system? The gauge was not hooked up when I bought the truck, whose previous owner had converted most everything to 12v. I've bench-tested the fuel sending unit with an ohmmeter and get a range of 0-98 ohms.

    It'll save me lots of bucks if I can keep using the old sending unit (by the way, I coated the cork with POR-15 gas tank sealer - I had bought the stuff before looking at the inside of my pristine, rust-free gas tank, so I used it on the sending unit float to "seal" it instead).

    Thanks for any replies and opinions, or just plain "Howdy"s.


    [img=left]http://simps.us/studebaker/misc/images/Current_Avacar.gif[/img=left] - DilloCrafter


    1955 1/2 Ton Pickup
    The Red-Headed Amazon

    Paul Simpson
    "DilloCrafter"

    1955 1/2 Ton Pickup
    The Red-Headed Amazon
    Deep in the heart of Texas

  • #2
    quote:Originally posted by DilloCrafter

    I'm wondering if I'll need to replace the fuel sending unit that's in my '55 truck, now that I've changed the fuel gauge to the 12v version. It's just a variable resistor in that sending unit, but can it handle 12v, since the one that's in there was part of a 6v system? The gauge was not hooked up when I bought the truck, whose previous owner had converted most everything to 12v. I've bench-tested the fuel sending unit with an ohmmeter and get a range of 0-98 ohms.

    It'll save me lots of bucks if I can keep using the old sending unit (by the way, I coated the cork with POR-15 gas tank sealer - I had bought the stuff before looking at the inside of my pristine, rust-free gas tank, so I used it on the sending unit float to "seal" it instead).

    Thanks for any replies and opinions, or just plain "Howdy"s.


    [img=left]http://rocketdillo.com/studebaker/misc/images/Current_Avacar.gif[/img=left] - DilloCrafter


    1955 1/2 Ton Pickup
    The Red-Headed Amazon
    Well, Howdy, then!

    I'm pretty certain you will have to change your sending unit, too. I believe the 12 volt sender has a resistance range of about 40-400 ohms versus 10-100 ohms for the 6 volt unit. It WILL be different, though.
    The specs on these are kind of hard to find, I think.

    If you simply installed a series resistor, the gage might read right at one point in its range.

    Seems to me there is a business opportunity for somebody well-versed in integrated circuit design to come up with a little box containing an Op amp and a transistor to sink current. Set it up so the gain of the Op amp could be varied over a wide range, and such a device could be used to operate just about any current-sensitive gage with any variable-resistance sender.

    But, for the time being, I'd say the easiest way out is to simply buy a 12 volt sending unit ('56-up Transtar), or maybe a "universal" Stewart-Warner 12 volt sending unit, assuming you used a S-W gage unit.

    Gord Richmond, within Weasel range of the Alberta Badlands
    Gord Richmond, within Weasel range of the Alberta Badlands

    Comment


    • #3
      I had a spare 12 volt truck sending unit that I threw in when I delivered the last truck that I sold. I then found out how much replacements cost and I now have another 12 volt truck. I guess I am still learning <G>.
      Gary L.
      Wappinger, NY

      SDC member since 1968
      Studebaker enthusiast much longer

      Comment


      • #4
        Thanks for the replies (and the Howdy). Gordon, I can always count on you for electrical help, it is much appreciated. All the 12v universal type sending units I found on the web seem to be the same - 240 ohms empty, 33 ohms full. Here's the cheapest one, at $35.74, including shipping: http://www.performancepartz.com/auto...t-p-22310.html. I'm going to assume the 12v Stewart Warner gauge is looking for that resistance range (I guess I can test it with a few resistors of different sizes, and a 12v power supply).

        Looking at the photo of it (see link above) that universal unit is physically "inverted" compared to the original Studebaker part. Notice that the pivot is at the bottom of the tank. Who knows, maybe it is more accurate.

        Or, the best price among our Stude vendors for the correct part is $53.50 at SASCO (not including shipping). So, I'll probably spend the extra $25 and get the Studebaker part, even though it's not correct to put a 12v sending unit in a '55 truck. Seems I won't let myself stray TOO far from original, even with the mild modifications I'm doing to the Red-Headed Amazon.

        [img=left]http://rocketdillo.com/studebaker/misc/images/Current_Avacar.gif[/img=left] - DilloCrafter


        1955 1/2 Ton Pickup
        The Red-Headed Amazon

        Paul Simpson
        "DilloCrafter"

        1955 1/2 Ton Pickup
        The Red-Headed Amazon
        Deep in the heart of Texas

        Comment


        • #5
          quote:Originally posted by DilloCrafter

          Thanks for the replies (and the Howdy). Gordon, I can always count on you for electrical help, it is much appreciated. All the 12v universal type sending units I found on the web seem to be the same - 240 ohms empty, 33 ohms full. Here's the cheapest one, at $35.74, including shipping: http://www.performancepartz.com/auto...t-p-22310.html. I'm going to assume the 12v Stewart Warner gauge is looking for that resistance range (I guess I can test it with a few resistors of different sizes, and a 12v power supply).

          Looking at the photo of it (see link above) that universal unit is physically "inverted" compared to the original Studebaker part. Notice that the pivot is at the bottom of the tank. Who knows, maybe it is more accurate.

          Or, the best price among our Stude vendors for the correct part is $53.50 at SASCO (not including shipping). So, I'll probably spend the extra $25 and get the Studebaker part, even though it's not correct to put a 12v sending unit in a '55 truck. Seems I won't let myself stray TOO far from original, even with the mild modifications I'm doing to the Red-Headed Amazon.

          [img=left]http://rocketdillo.com/studebaker/misc/images/Current_Avacar.gif[/img=left] - DilloCrafter


          1955 1/2 Ton Pickup
          The Red-Headed Amazon
          If the 12 volt gauge you have installed is a genuine Studebaker gauge, I'd get the correct sending unit from SASCO, because it should work right out of the box with that gauge. If the 12 volt gauge is some kind of aftermarket part, there's no guarantee it will work with ANY sending unit other than the one it was meant to.

          The universal sending unit needs to be set up to work in your tank; i.e. the float arm has to be configured the right way so that the arm makes a full excursion from one stop to the other as the fuel level in the tank changes. Given that it could well take several hours of your time to get it right, the extra $20 doesn't look so bad.

          Gord Richmond, within Weasel range of the Alberta Badlands
          Gord Richmond, within Weasel range of the Alberta Badlands

          Comment


          • #6
            Update: Although the gauges and wiring are not in my truck yet, I was able to mount a NOS 12v Studebaker (Stewart Warner) fuel gauge in the gauge panel on a bench, attach leads to a 5k ohm potentiometer, and connect it to a 12v power supply (my battery charger, putting out 11.5v). With the potentiometer at 240 ohms, the gauge reads empty, and at around 33 ohms, it slowly creeps up to Full. I rotated the pot until the gauge read exactly at the 1/2 tank mark, disconnected power leads from the potentiometer, and measured 110 ohms. I'm guessing it would read 1/2 tank at a slightly higher resistance if another volt were being put out (such as by an alternator, typically over 12v).

            I hope this info will be useful to anyone else in this situation.

            Also, I found that Summit Racing has a Stewart Warner fuel sending unit (33 - 240 ohm) that is adjustable. I may have to go ahead and get it since SASCO has a 2 or 3 month wait on their sending units. Otherwise, I would buy from a Stude vendor (hard to beat the $27.95 price for this adjustable sending unit, and at least it is Stewart Warner, same as the NOS gauge).


            [img=left]http://rocketdillo.com/studebaker/misc/images/Current_Avacar.gif[/img=left] - DilloCrafter


            1955 1/2 Ton Pickup
            The Red-Headed Amazon

            Paul Simpson
            "DilloCrafter"

            1955 1/2 Ton Pickup
            The Red-Headed Amazon
            Deep in the heart of Texas

            Comment


            • #7
              Normally I would never recommend J.C. Whitney as I have not had much luck with their crap. However, they sell two adjustable, universal fuel sending units, one for GM vehicles that is a 12-volt, 0-90 ohm unit, and a 240-33 ohms one for "all vehicles with Stewart-Warner guages." Either is $17.99. At that price, it might be worth a try. I have the 0-90 ohm unit in a non-stock gas tank in my M truck, with a GM guage istalled behind the original guage face. It works fine and looks stock.

              jj

              Comment


              • #8
                Thanks, JJ. That's a very tempting price.

                I'm still inclined to go with this one at Summit, for two reasons

                1) It's a Stewart Warner brand gauge, like the original
                2) It's pivot point is at the top of the tank, like the original.

                All the other universal ones I've seen have the pivot at the bottom of the tank. Not that that's worse or better, it's just that I feel a bit closer to original with the Stewart Warner model seen at this link
                Here's a shot of it:


                [img=left]http://rocketdillo.com/studebaker/misc/images/Current_Avacar.gif[/img=left] - DilloCrafter


                1955 1/2 Ton Pickup
                The Red-Headed Amazon

                Paul Simpson
                "DilloCrafter"

                1955 1/2 Ton Pickup
                The Red-Headed Amazon
                Deep in the heart of Texas

                Comment


                • #9
                  quote:Originally posted by jjones

                  Normally I would never recommend J.C. Whitney as I have not had much luck with their crap. However, they sell two adjustable, universal fuel sending units, one for GM vehicles that is a 12-volt, 0-90 ohm unit, and a 240-33 ohms one for "all vehicles with Stewart-Warner guages." Either is $17.99. At that price, it might be worth a try. I have the 0-90 ohm unit in a non-stock gas tank in my M truck, with a GM guage istalled behind the original guage face. It works fine and looks stock.
                  I tried the JC. Whitney site and did not find the unts. do you have a link? I thought for $18 I could get it to just hook up to gauge nd see how it responds when rotated. thanks
                  Mike D
                  jj
                  Mike DeLapp
                  Barrington, IL
                  53 Commander Hardtop

                  Comment


                  • #10
                    jj; here is the current catalog #713J-08, Pg.130, item # RB128-526 (240-33 OHM) $17.99 Adjustable float with arm at the bottom.

                    [quoteI tried the JC. Whitney site and did not find the unts. do you have a link? I thought for $18 I could get it to just hook up to gauge nd see how it responds when rotated. thanks
                    Mike D jj[/quote]

                    StudeRich
                    Studebakers Northwest
                    Ferndale, WA
                    StudeRich
                    Second Generation Stude Driver,
                    Proud '54 Starliner Owner

                    Comment


                    • #11
                      I recommend authentic Stewart Warner, since that's who made your gauges.

                      Here is the link to the one at Summit Racing:

                      http://store.summitracing.com/partde...5&autoview=sku

                      While the J.C. Whitney sending unit is $10 less, it is configured differently. You need to adjust the overall height, as the potentiometer and pivot point sit at the bottom of the tank.

                      On the other hand, the Stewart Warner version from Summit Racing is configured the same as the original, with the potentiometer, and thus, the pivot point, at the top of the tank. It is a universal type unit, so you must measure and cut the rod before assembling it. This is the kind I bought, and had no trouble preparing it and installing it in my truck.

                      [img=left]http://rocketdillo.com/studebaker/misc/images/Current_Avacar.gif[/img=left] - DilloCrafter

                      1955 1/2 Ton Pickup
                      The Red-Headed Amazon
                      Deep in the heart of Texas

                      Paul Simpson
                      "DilloCrafter"

                      1955 1/2 Ton Pickup
                      The Red-Headed Amazon
                      Deep in the heart of Texas

                      Comment


                      • #12
                        J.C. Whitney catalogue 707B-02, page 138: CM132950 for GM 0-90 ohms; CM128526 for all vehicles with 240-33 ohm Stewart-Warner gauges. As I said before, I seldom buy from Whitney because of quality concerns, but the GM unit in my M truck has been trouble-free so far.

                        jj

                        Comment


                        • #13
                          I installed the S.W. sending unit from Summit exactly like the one Dillo has pictured, in my 60 Lark, it is working perfectly.


                          Studebaker Fever
                          60 Lark
                          51 Champion
                          Phil
                          Arnold, Missouri

                          Studebaker Fever
                          60 Lark
                          56 Power Hawk
                          Phil Hendrickson
                          Arnold, Missouri

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