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  • Fuel tank access

    Is there fuel tank access from the trunk or do I need to drop the tank to get to the float /pickup device? I have a gas gauge that has only worked 2 times for a short drive since I got the car. I assume it could be a ground issue from the unit wiring or I need to replace it all.
    Tim
    1962 Conv Tbird
    1993 Miata LE
    1994 Miata

  • #2
    Yes, you can get to the sender through the access panel in the trunk.

    John
    John Pizzi - Squarebirds Administrator

    Thunderbird Registry #36223
    jopizz@verizon.net 856-779-9695

    http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

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    • #3
      What are my chances it is just bad. I know (I thought anyway) that a bad ground can also cause a malfunctioning gauge?
      Tim
      1962 Conv Tbird
      1993 Miata LE
      1994 Miata

      Comment


      • #4
        reading other threads on gas tank gauge issues. What is the CRV? My temp gauge is working.
        Tim
        1962 Conv Tbird
        1993 Miata LE
        1994 Miata

        Comment


        • #5
          Fuel tank access

          Hi Tim, If that is the original fuel sending unit in the tank, the chances of it having gas in the float, or being defective are good. After all, it is probably as old as you are! The CVR unit is the Constant Voltage Regulator which, in the case of our Squarebirds, and probably your Tbird, located on the back of the instrument panel. The CVR unit takes the 12v from the battery and changes it to an oscillating 0-6V for the 6V gauges in these old Tbirds of our. Yes, the gauges are 6v. What can happen if the CVR unit fails is that the 12v can go right through the CVR unit and attack the wiring of the gauges. The fact that your Temp gauge and others are still working well indicates that your CVR is okay. You may have a problem with the fuel sending unit in the tank. I did on my Squarebird, and when I pulled it out I found the plastic (in some cases metal) float was full of gas. And after some 50+ years of use, the electrical rheostat on it was all corroded and shot. So I bought a new one, and replaced it, grounded it properly and that fixed that problem. Plus, as many of us do, I also added a heavy ground wire to the flange of the gas tank, cleaned off a good spot on the frame and grounded the tank to that. Just make sure if you drill a hole in the tank that it is NOT the tank itself, but a flange where no gas is... Try these things and that might fix your problem. BTW, IF that CVR unit ever goes out on you, you DO risk the 12v getting to the gauges and frying the wiring. It costs several hundred bucks to get those gauges fixed. Ask me how I know... lol.. Our dynamic webmaster, Dave Dare ~ simplyconnected, has a special he runs for our users who become Paid Members, which I see you are not. $20yr paid through PayPal gets you many additional advantages that non-Paid members do not have. One of them is a discount on buying his solid state CVR unit, guaranteed for life. He would need you to send him your CVR unit off your instrument panel so he can build his solid state CVR unit in it and send it back to you. His unit is set up to prevent 12v from going to the gauges should it fail. To my knowledge, none have to this point. You might want to check into this. This is a good way to say a bit of money and become a Paid Member. The money from Paid Memberships is what keeps this Forum going, and helps pay the server bills.... For more information on Paid Memberships, check up the top of the Forum and you will find the information there in the Announcements section.

          Ray Clark - Squarebirds Administrator
          '59 Tbird "The Yellow Rose Of Texas" aka "Tweety Bird"
          "It's Hip To Be Square"
          Thunderbird Registry #33025 VTCI #11178

          Contact me via Private Message for my email address, or (Cell) 210-875-1411 (Home) 210-674-5781

          http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

          Comment


          • #6
            I just read up on the CRV and it touched on things you just wrote, sorry you had to write all that. My temp gauge works fine, it stays cool and goes up to the same point every time where the car is at running temp. The gas gauge always goes to about 1/4 and sits there when full or thereabouts. It may go down some but I am so scared to run out of gas I keep it fuel after so many miles of driving. Only two times has it read what I thought was correct.
            Seems my issue could be sending unit/float or ground?
            Tim
            1962 Conv Tbird
            1993 Miata LE
            1994 Miata

            Comment


            • #7
              You may have gas in the float. That would cause the gauge to never go up to the full mark. It could also be a bad ground. You can ground the sender with out removing it. Remove the access panel and clip a wire from the sender to the body of the car. If the gauge works correctly then it's a ground issue. If it still stays at 1/4 then it could be the sender itself that's bad or the float as I mentioned. You will have to remove the sender to find out.

              John
              John Pizzi - Squarebirds Administrator

              Thunderbird Registry #36223
              jopizz@verizon.net 856-779-9695

              http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

              Comment


              • #8
                Fuel tank access

                Tim, I understand the problem, because I have the same thing on my Squarebird. I do not trust it below 1/4 of a tank, having run out of gas once. However, IF, and I think it is, your Bulletbird fuel and temp gauge is like the Squarebirds, there is an adjustment on the back of that gauge. There is one on the top for the Fuel Gauge and one on the bottom for the Temp gauge. There are two little gears on the left and the right at the top for the Fuel gauge and a matching set of gears at the bottom for the Temp gauge. To get to this gauge you are going to have to take that gauge out of the instrument panel. With either the gas tank empty or as full as you can get it (providing your fuel sending unit float is not full of gas. You may want to check that first), you can turn the gears with a small screwdriver slightly while watching the gauge (still hooked up to power) and watch to see if it goes up or down in reading. I have forgotten if the left hand gear adjusts it down or up, but I think down, and I think the right side raises the reading up. You will have to play with it to see what it does. If the tank is Full, it should be sitting on the F. If it I Empty, it should be sitting on the E. Since you are happy with where the Fuel gauge is reading do NOT touch it.

                Ray Clark - Squarebirds Administrator
                '59 Tbird "The Yellow Rose Of Texas" aka "Tweety Bird"
                "It's Hip To Be Square"
                Thunderbird Registry #33025 VTCI #11178

                Contact me via Private Message for my email address, or (Cell) 210-875-1411 (Home) 210-674-5781

                http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

                Comment


                • #9
                  I am not happy, ha ha ha. It is always at 1/4 full, drops down a little when I drive some gas out of it, I think. Hard to tell. When I fill the tank it stays at the place. Two times the gauge has read what I feel is the correct reading just based on knowing what gas amount was in the tank. Since the other gauges work, I feel it is maybe ground or float/sending unit issue.
                  Talk of gears? Have not read anything about that.
                  Tim
                  1962 Conv Tbird
                  1993 Miata LE
                  1994 Miata

                  Comment


                  • #10
                    If your gauge only goes up to 1/4 most of the time it's not an adjustment problem with the gauge. What Ray is talking about is for making minor adjustments. That's not what you are describing.

                    John
                    John Pizzi - Squarebirds Administrator

                    Thunderbird Registry #36223
                    jopizz@verizon.net 856-779-9695

                    http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

                    Comment


                    • #11
                      So I got to the tank access from the trunk. There is one wire coming out of tank. First of all I used my circuit tester for a ground wire. If I grounded the wire coming to the tank, the gauge would only go to 3/4 and the test light blinked, I assume that the circuit is good then? It was not till later when after I put everything back together that a little further up the harness wire to tank the wire to the tank had TWO inside of it. Anyway, where the wire from gauge to wire from tank connect, if I left a little of the metal male plug stick out that was connected to the female plug and clip my test to that metal pc and grounded it the gauge went to full.
                      When I filled it last I have put about 40 miles on the car. Assuming I pull 10 MPG could it still be reading full? Note if I bounced the rear end up and down the gauge did not budge as I thought it would as many old car gauges do from back in the day.
                      So I put it all back together. I scrapped off a part of the lip on the tank and ran a ground (my test light) to the car (several diff places), gauge just stayed at 1/4 full as it always is since I got it.
                      So I don't know, seems to me I have a bad sending unit?
                      Tim
                      1962 Conv Tbird
                      1993 Miata LE
                      1994 Miata

                      Comment


                      • #12
                        You have a 20 gallon tank. At 10 mpg you only used 4 gallons so it should read above 3/4. If you ground the wire to the sender and the gauge goes up then the circuit is good. Since you grounded the sender to the body of the car and it didn't change the problem is with the sender.

                        John
                        John Pizzi - Squarebirds Administrator

                        Thunderbird Registry #36223
                        jopizz@verizon.net 856-779-9695

                        http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

                        Comment


                        • #13
                          ok I am confused or I confused you. Your reply confused me.
                          When I disconnect the wire from sending unit in tank from the wire coming from the gauge (which appears to have two wires in it??)
                          If I ground that wire end female plug from gauge, the gauge reads to 3/4.
                          If I plug the wire from tank into the wire from gauge leaving a little metal exposed yet both connections are connected and I ground it, the tank goes to full line every time I do it.
                          If I plug it all together and try to ground tank it just stays at 1/4 as always.
                          Tim
                          1962 Conv Tbird
                          1993 Miata LE
                          1994 Miata

                          Comment


                          • #14
                            You have the wire connected to the sender and you ground the sender to the body of the car and the gauge stays at 1/4. That proves that the ground to the tank is not the issue. You remove the wire from the sender and you ground it and the gauge goes up. That proves that the gauge is working. Why the gauge only goes to the 3/4 mark when you ground the end of the wire and the full mark when you ground the connector in the harness is odd. You can run a new piece of wire and see if it changes. Regardless the main problem is with the sender.

                            John
                            John Pizzi - Squarebirds Administrator

                            Thunderbird Registry #36223
                            jopizz@verizon.net 856-779-9695

                            http://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

                            Comment


                            • #15
                              you say sending meaning sending unit in tank. If I pull that wire out of wire from gauge, and ground the wire from said tank, why would it do anything, what does it have to send, it has no power to it. Sorry been a hot day at work. This is going over my head.
                              Tim
                              1962 Conv Tbird
                              1993 Miata LE
                              1994 Miata

                              Comment

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