CX2400 fuel gauge not working
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Thread: CX2400 fuel gauge not working

  1. #1
    Fellow Frogger! Jinandfonic's Avatar
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    Default CX2400 fuel gauge not working

    I'd thought I'd asked the brains trust before attempting this repair. Where should I start?


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    Now go make me a sandwich Hotrodelectric's Avatar
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    Quote Originally Posted by Jinandfonic View Post
    I'd thought I'd asked the brains trust before attempting this repair. Where should I start?


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    How is it not working? Completely dead? Erratic? Goes immediately to a point and stops no matter how much fuel? You DO have gas in the tank, right?
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    1000+ Posts gerrypro's Avatar
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    These items are real fun to get working properly. It necessitates removing the tank to remove the sender. The sender will dismantle easily but take care if the fixing nut is seized at the base. This is found once the filter cap at the base is removed. Under no circumstances twist the top in relation to the body when separating. You can easily damage the earthing wire for the low level indicator. The float is held together with plastic pins that are burred over to retain. Separate the float to access the contact and its spring. The contact may be worn or there may be insufficient tension to hold it in place against the resistance coil. It must contact this coil and the brass central rod to make a circuit. Clean the rod and the contacts thoroughly and check that the spring allows the contact to ride against the rod. Too firm and the float will not rise and too loose and it will not complete the circuit.
    Mine now works perfectly after a lot of fiddling!
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    Cheers Gerry

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    Fellow Frogger! Jinandfonic's Avatar
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    Quote Originally Posted by Hotrodelectric View Post
    How is it not working? Completely dead? Erratic? Goes immediately to a point and stops no matter how much fuel? You DO have gas in the tank, right?
    Hehe, yes gas in the tank. Just nothing registers at all & always reads empty with light on. I'll have to count kilometres driven till guessing to fill up. I gather there is a sender unit in tank with a float. Wiring from there. I know instrument circuit boards can be a weak point yet everything else seems to work.


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    Now go make me a sandwich Hotrodelectric's Avatar
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    Quote Originally Posted by Jinandfonic View Post
    Hehe, yes gas in the tank. Just nothing registers at all & always reads empty with light on. I'll have to count kilometres driven till guessing to fill up. I gather there is a sender unit in tank with a float. Wiring from there. I know instrument circuit boards can be a weak point yet everything else seems to work.


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    You would not believe how many times I've asked if there was fuel in the tank, come to find out there was so little it wouldn't lift the float enough to to register

    Gerry has it pretty comprehensively laid out what you need to do for an actual fix. I would make two suggestions though, before you pull the tank- bit of a bitch job on almost any car. First, firmly clamp a test lead from the tank- any flange will do- to earth somewhere on the chassis. Flip on the ignition, and see if you get a response. IF you can reach the wiring, see if you can pull the connection off the top of the sender. Ground that wire, and see if the gauge reacts. Second, very carefully check the wiring along it's route if it's accessable. Any break in the wire will cause what you're experiencing. If you're feeling really brave, you can do a continuity check on that wire between the sender and the gauge. That will require pulling the cluster- or, at least the upper 1/2 of the croissant. Hopefully you can do these checks without pulling the tank. Oh- and of course- make sure you're getting 12v ignition + at the gauge. None of what I or Gerry says will help if you aren't getting power to begin with.
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    Fellow Frogger! Jinandfonic's Avatar
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    Quote Originally Posted by Hotrodelectric View Post
    You would not believe how many times I've asked if there was fuel in the tank, come to find out there was so little it wouldn't lift the float enough to to register

    Gerry has it pretty comprehensively laid out what you need to do for an actual fix. I would make two suggestions though, before you pull the tank- bit of a bitch job on almost any car. First, firmly clamp a test lead from the tank- any flange will do- to earth somewhere on the chassis. Flip on the ignition, and see if you get a response. IF you can reach the wiring, see if you can pull the connection off the top of the sender. Ground that wire, and see if the gauge reacts. Second, very carefully check the wiring along it's route if it's accessable. Any break in the wire will cause what you're experiencing. If you're feeling really brave, you can do a continuity check on that wire between the sender and the gauge. That will require pulling the cluster- or, at least the upper 1/2 of the croissant. Hopefully you can do these checks without pulling the tank. Oh- and of course- make sure you're getting 12v ignition + at the gauge. None of what I or Gerry says will help if you aren't getting power to begin with.
    Many thanks H. I will do those tests first. I have to replace the cracked filler tube so two jobs at the same time is the aim. Btw I couldn't find any previous posts/topics in this regards. Lost in the crash?


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    i would second that. isolate the problem between the sender and the gauge by shorting the earth wire( only for short period of time to see if you get any movement) otherwise you will burn out gauge.

    if sender then check resistance over the travel of the sender.

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    Now go make me a sandwich Hotrodelectric's Avatar
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    Quote Originally Posted by Jinandfonic View Post
    Many thanks H. I will do those tests first. I have to replace the cracked filler tube so two jobs at the same time is the aim. Btw I couldn't find any previous posts/topics in this regards. Lost in the crash?


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    Possibly. I don't know if that specifically was lost. There is a dedicated thread I think in 'Froggy Chat' that may help find it if there ever was one.

    Quote Originally Posted by benvv View Post
    i would second that. isolate the problem between the sender and the gauge by shorting the earth wire( only for short period of time to see if you get any movement) otherwise you will burn out gauge.

    if sender then check resistance over the travel of the sender.
    A couple of excellent bits to remember. I don't know what the specific values are supposed to be, but yah, as you wipe the contacts arm against the resistor winding you need to see a change in resistance.
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    I think your float might have sunk. The rest sounds like the wiring etc. is Ok.

    Tank isn't too difficult to get out- there's a tension bolt for the strap under the boot mat just in front of the boot catch (or trunk lid if you prefer...)

    The filler neck can be a bit fragile and very unco-operative, from memory, if the tank is kept in the straps and lowered only at the back it isn't necessary to disconnect the fuel lines, which go onto the gauge unit anyway. The might crack from age though.

    Have fun!

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    Quote Originally Posted by Bruce Llewellyn View Post
    I think your float might have sunk. The rest sounds like the wiring etc. is Ok.

    Tank isn't too difficult to get out- there's a tension bolt for the strap under the boot mat just in front of the boot catch (or trunk lid if you prefer...)

    The filler neck can be a bit fragile and very unco-operative, from memory, if the tank is kept in the straps and lowered only at the back it isn't necessary to disconnect the fuel lines, which go onto the gauge unit anyway. The might crack from age though.

    Have fun!
    Thanks for the heads up Bruce. Yes my filler pipe is cracked so two jobs to do down here.


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    1000+ Posts gerrypro's Avatar
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    Quote Originally Posted by Bruce Llewellyn View Post
    I think your float might have sunk. The rest sounds like the wiring etc. is Ok.

    Tank isn't too difficult to get out- there's a tension bolt for the strap under the boot mat just in front of the boot catch (or trunk lid if you prefer...)

    The filler neck can be a bit fragile and very unco-operative, from memory, if the tank is kept in the straps and lowered only at the back it isn't necessary to disconnect the fuel lines, which go onto the gauge unit anyway. The might crack from age though.

    Have fun!
    Undo the lines at the rubber hose at the main fuel line and return line joints, not the rubber line to tank sender /pick up unit. Drain and remove the entire tank! It makes life a lot easier!!!!!!!!
    The odds are that you will have to clean all the internal contacts of the sender unit and also make sure that the contacts are riding properly on the centre rod as well as the resistance coil. I used a multi-meter to check the resistance as the float slid up and down the coil. If you get an infinity reading you have an open circuit!
    Do it once do it right!!!!!
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    Cheers Gerry

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    Fellow Frogger! Jinandfonic's Avatar
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    Thanks Gerry will do. Is there a specific product that is best to use on the cracked plastic filler pipe that anyone can recommend?
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  13. #13
    Real cars have hydraulics DoubleChevron's Avatar
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    before you go messing with the tank... Pull the carpet out of the boot and see if there is an access hole. Later cars have an access hole in the boot floor for the sender. I'm not sure what year they started stamping this out though.

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    Fellow Frogger! Jinandfonic's Avatar
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    Quote Originally Posted by DoubleChevron View Post
    before you go messing with the tank... Pull the carpet out of the boot and see if there is an access hole. Later cars have an access hole in the boot floor for the sender. I'm not sure what year they started stamping this out though.

    seeya,
    Shane L.
    Sadly neither my '76 or '78 has the access. I just have the hole in the head for doing these crazy restorations!
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