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Thread: '56 Riviera Fuel gauge query

  1. #1
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    '56 Riviera Fuel gauge query

    I recently imported a '56 Special Riviera to the UK from Nashville - lovely car but with the usual old car Electrical gremlins, one of which is the fuel gauge.

    It moves up to around the empty mark when the ignition is turned on but doesn't go any further so the first thing I did was disconnect the wire in the trunk that goes to the tank sender - the gauge pegged to the far right past the Full mark which kind of threw me a bit.

    I haven't had time to look further but assume that the gauge works by in the normal GM way of varying ground resistance so am puzzled why the gauge went up when the wire was disconnected.

    Any thoughts ???

  2. #2
    the 57 chassis manual, which should theoretically be very similar, is here:

    https://www.teambuick.com/reference/...ssis/index.php

    57 is the first year of the 364ci though, so there may have been a major redesign from 56 when they were still using the 322ci.

    unfortunately, the closest thing we have in the other direction is the 52 Service manual, which is prior to the introduction of the Nailhead and still used a straight 8. that manual is here:

    https://www.teambuick.com/reference/...shop/index.php


    according to the 57 diag page, a short across the fuel level sender should read empty and an open circuit should read full ... so it would appear that the problem is within the sending unit itself, not with the circuit to the dash.

    this could be mechanical or electrical in origin.

    the first thing i would check would be that the tank float actually moves up and down ( ie, isn't sunk at the bottom of the tank and never moves ) AND is properly coupled to the potentiometer.

    once you've verified that the mechanicals are working properly, put a multimeter across the sending unit. obviously, minimum resistance ( close to zero ) should show when the float is at the bottom and resistance should rise fairly smoothly as the float moves to the top of the tank.

    i would suggest getting a can of electrical contact cleaner if the pot gives jumpy readings as the tank fills ... but if it's showing shorted regardless of the position of the wiper you'll probably have to get a new rheostat on there. sketchy resistance values are typically due to corrosion or grime building up between the wiper and the carbon resistor element which means that R goes *up* the more the pot deteriorates.

    https://en.wikipedia.org/wiki/Potentiometer
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  3. #3
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    '56 Riviera and '70 Electra fuel gauge problems

    Quote Originally Posted by bob k. mando View Post
    the 57 chassis manual, which should theoretically be very similar, is here:

    https://www.teambuick.com/reference/...ssis/index.php

    57 is the first year of the 364ci though, so there may have been a major redesign from 56 when they were still using the 322ci.

    unfortunately, the closest thing we have in the other direction is the 52 Service manual, which is prior to the introduction of the Nailhead and still used a straight 8. that manual is here:

    https://www.teambuick.com/reference/...shop/index.php


    according to the 57 diag page, a short across the fuel level sender should read empty and an open circuit should read full ... so it would appear that the problem is within the sending unit itself, not with the circuit to the dash.

    this could be mechanical or electrical in origin.

    the first thing i would check would be that the tank float actually moves up and down ( ie, isn't sunk at the bottom of the tank and never moves ) AND is properly coupled to the potentiometer.

    once you've verified that the mechanicals are working properly, put a multimeter across the sending unit. obviously, minimum resistance ( close to zero ) should show when the float is at the bottom and resistance should rise fairly smoothly as the float moves to the top of the tank.

    i would suggest getting a can of electrical contact cleaner if the pot gives jumpy readings as the tank fills ... but if it's showing shorted regardless of the position of the wiper you'll probably have to get a new rheostat on there. sketchy resistance values are typically due to corrosion or grime building up between the wiper and the carbon resistor element which means that R goes *up* the more the pot deteriorates.

    https://en.wikipedia.org/wiki/Potentiometer
    I've still not had time to look at the '56 fuel gauge but will do either today or tomorrow - i also need to sort a similar problem on my '70 Electra 225 Coupe. On this car the gauge creeps up when the ignition is off but pegs to Empty as soon as the ignition is turned on. Is this more likely to be the sender unit or gauge ?

    I imported this one owner car from the US last year but have only just started working on it. Turns out that mice had been snacking on the interior before I got it so may have also been at the wiring. Luckily most of the damage isn't visible other than a 3" hole right through the rear seat where the base meets the back - the seatbelt was covering it so I didn't see it when buying the car. I only noticed it when fixing the passenger side rear window motor plastic roller which had disintegrated (I didn't have one so drilled the locating pin out and used a 1963 Ford thunderbird roller which, with a few minor mods, worked perfectly).

  4. #4
    we have the 71 chassis manual but the GM big cars moved to a new design in 71 so you'll probably find the 67 manual more relevant for the Electra:

    https://www.teambuick.com/reference/...ssis/index.php


    On this car the gauge creeps up when the ignition is off but pegs to Empty as soon as the ignition is turned on. Is this more likely to be the sender unit or gauge ?



    maybe a bad capacitor bleeding current?

    i hope it's not wires shorted in the harness, that can be a pain.
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  5. #5
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    '56 Riviera Fuel gauge query

    Quote Originally Posted by Rustytractor View Post
    I recently imported a '56 Special Riviera to the UK from Nashville - lovely car but with the usual old car Electrical gremlins, one of which is the fuel gauge.

    It moves up to around the empty mark when the ignition is turned on but doesn't go any further so the first thing I did was disconnect the wire in the trunk that goes to the tank sender - the gauge pegged to the far right past the Full mark which kind of threw me a bit.

    I haven't had time to look further but assume that the gauge works by in the normal GM way of varying ground resistance so am puzzled why the gauge went up when the wire was disconnected.

    Any thoughts ???

    Bob's right with the diagnosis above, but I would add to that, don't turn on the ignition with the sending unit unhooked for longer than a couple seconds. preferably not at all. this can ruin the gauge.

    I have a 56 Buick, and did all of my wiring work and your gauge is doing exactly what it should do! sounds like you either have a bad sending unit, bad ground, or bad wire between the sending unit and gauge.

    Also, if you need any 56 buick parts let me know, I've got a barn full

  6. #6
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    Quote Originally Posted by jacob View Post
    Bob's right with the diagnosis above, but I would add to that, don't turn on the ignition with the sending unit unhooked for longer than a couple seconds. preferably not at all. this can ruin the gauge.

    I have a 56 Buick, and did all of my wiring work and your gauge is doing exactly what it should do! sounds like you either have a bad sending unit, bad ground, or bad wire between the sending unit and gauge.

    Also, if you need any 56 buick parts let me know, I've got a barn full
    thsnks for replying. Am I looking for a bad ground at the gauge or sender end (or possibly either/both?)

  7. #7
    test test
    The way to crush the bourgeoisie is to grind them between the millstones of taxation and inflation.
    Vladimir Lenin

    Government schooling is about "the perfect organization of the hive."
    H.H. Goddard, Human Efficiency (1920)

  8. #8
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    '56 Riviera Fuel gauge query

    Quote Originally Posted by Rustytractor View Post
    thsnks for replying. Am I looking for a bad ground at the gauge or sender end (or possibly either/both?)


    The sending unit is grounded through the gas tank, which is grounded through the straps that hold the gas tank. If you pull the gas tank, hook up a ground wire from the frame (or anywhere really) to the base of the sending unit, turn the ignition on, and physically move the float up and down you should see the gauge move. if its still only moving a little bit, then I would replace the sending unit.

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