‘93 W900L fuel gauge quit

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mile marker 27, May 9, 2021.

  1. mile marker 27

    mile marker 27 Medium Load Member

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    Maybe not and probably not the gauge but nonetheless, it’s not reading properly. What’s more than likely my problem? I’ve got an ‘89 W9B, that the gauge has never worked so, possibly the same issue. Any help is appreciated.
    Been using an old wooded yard stick, that I slide into the the tank straps. Works but.....
     
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  3. Joyce's Volvo

    Joyce's Volvo Light Load Member

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    Take note of the reading of the gauge , take the wire loose from the sending unit at the tank or tanks, you can ground (arc) the lead to the gauge , it should show full or be "pegged" if gauge is getting a reading. No movement means no connection or no power to gauge , if it moves , check sending unit in tank. The sending unit is a reastat that limits ohms to the gauge (more ohms , more gauge reads) . Use a ohm meter and connect to the sending unit and ground, reach in tank with stick or suitable same and move the float up and down , meter should show more or less ohms.
     
  4. Rideandrepair

    Rideandrepair Road Train Member

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    I had one go bad on a 92 WS. Took the screws out, pulled the whole sending unit/float out. Had a wire, maybe a metal rod? broken off, I forget exactly, but it was obvious, drilled a hole, put the wire/rod back on with a screw. Bent the arm a bit to make it more accurate. You can pull it out, make sure the float doesn’t have a hole in it. Check the wires. Pretty sure it was a wire.
     
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  5. wore out

    wore out Numbered Classic

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    Hole in the float is pretty common. They went to using plastic instead of brass. Where the float snaps into sending unit will tear
     
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  6. mile marker 27

    mile marker 27 Medium Load Member

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    Truck has dual 150 gallon tanks. Is there a sending unit in each tank?
     
  7. Joyce's Volvo

    Joyce's Volvo Light Load Member

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    Their will be a switch on the dash to switch from left tank to right tank. ( very rare to have 2 gauges) If in either postition you aren't getting a reading , check the power supply to the gauge, more than likely both sending units won't go down at the same time. Their won't be any power to the switch because it's for the ohm side of each tank. if you have such a switch (L/R) yes 2 sending units. Before they tried to improve what was working, you had a cross over that balanced both tanks by gravity, used from 1 tank only and feed from the other as needed to balance . Now most have a T block on supply and return over the tranny , get a little something in it and 1 side will be full and your out of fuel or fuel will spill out of the tank because of return to that tank that isn't balancing ( been there- done that ). New and improved ain't always better.
     
    Last edited: May 11, 2021
    Reason for edit: Forgot supplemental info
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  8. lester

    lester Road Train Member

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    Never driven one but I thought it was common on the W-9 to only have a sending unit in one tank? Heard of a few people running out of fuel because of that
     
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  9. Rideandrepair

    Rideandrepair Road Train Member

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    I’ve only dealt with WS and Frieighliners, only 1 sending unit, in Drivers side tank. Easy enough to figure out. Look for wires on top of tank. Mine are about 3” round, 4 screws holding it. Take 2 wires off. Take 4 screws out, while sending unit/arm with float lifts out as one assembly. Might be able to repair float or a broken wire, if parts aren’t readily available. You can also adjust the guage reading, by bending the rod a bit, if needed. Bending it up, will make it read empty, when it isn’t quite empty. Visa versa.
     
    Last edited: May 15, 2021
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