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    Thread: Fuel gauge stuck on empty.

    1. Junior Member
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      Apr 21st, 2013
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      Woodbridge NJ
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      1999 Cabrio, 2002 Mustang
      04-26-2014 04:09 PM #1
      Hey, how's everyone doing. I'm hoping someon can provide some insight into this issue. My wife has a 99 mk3 Cabby that for some reason decided that the fuel level was top secret info and is stuck on empty. I'm trying to figure out if it's the cluster gauge or the sensor on the fuel sender. I went digging in the trunk today with my multimeter and on the connector, plugged in, with the car running I read 4.5 volts on pin 3 (brown w/ blue stripe) but read only -0.16 volts on pin 2 (purple wire).

      I figured the sensor may have died because of the lack of voltage on pin 2. To try and test this I put the ignition in the ACC possition and unplugged the connector. I then connected pins 2 and 3 with a piece of wire thinking that applying voltage to pin 2 would cause the fuel gauge to shoot up to full but it still sat at empty.

      I'm not sure if this is the right way to test this. Does anyone know how I would be able to confirm before I start buying parts?
      Last edited by tdubs329; 04-26-2014 at 05:58 PM.

    2. Member briano1234's Avatar
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      90, 92, 93 Cabriolet They own you.
      04-26-2014 07:22 PM #2
      senders are a potentiometer.
      They vary ground to the meter in the dash.

      Take the wire that runs to the sender, and remove the connector to the fuel pump and /sender.
      Apply 9V +dc to that wire as well as ground to the ground wire or frame. If your gauge doesn't move, then it is a break in the wire between the sender , and or the gauge.

      If the gauge moves to full, then it is the sender.

    3. Junior Member
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      Apr 21st, 2013
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      1999 Cabrio, 2002 Mustang
      04-26-2014 07:30 PM #3
      Thanks for the reply. I'll give that a shot and see how it works out.

    4. Junior Member
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      1999 Cabrio, 2002 Mustang
      04-27-2014 01:19 PM #4
      Alright, so I just got done running this test with a 9 volt battery. I didn't get any movement on the needle. Just so that I am clear these are the steps I completed

      • disconnected the 4 pin connector from fuel sender
      • put ignition in RUN possition
      • connected (-) battery terminal to car frame (I made sure this was a good ground by testing continuity with brown wire on the 4 pin connector)
      • connected (+) battery terminal to the violet wire


      There was no movement on the needle so I then reversed the polarity. (-) terminal connected to wire, (+) connected to frame. There was still no movement on the needle. Is this the correct way to do this test?

      I guess the next thing I need to do is to pull the cluster gauge and see of I'm getting current on pin 21, on the 28 pin connector.

    5. Junior Member
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      1999 Cabrio, 2002 Mustang
      04-29-2014 05:54 PM #5
      I just wanted to follow up to see if anyone had any idea if I was testing this correctly.

    6. Junior Member
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      1999 Cabrio, 2002 Mustang
      05-03-2014 06:25 PM #6
      Well, I have confirmed that it's the sender. I pulled the cluster today and tried the battery test on that to see if it worked. I connected the (-) terminal to pin number 5, and the (+) terminal to pin 21 on the cluster and the fuel gauge shot up to full. After reading my Bentley again I realized what I was doing wrong with the test I tried last week on the 4 pin connector at the fuel sender. For anyone that ever needs to test this issue in the future the following is the procedure that I used to confirm there wasn't a break in the wire

      • disconnected the 4 pin connector from fuel sender
      • connected (-) battery terminal to the violet wire (pin 2 - ground wire)
      • connected (+) battery terminal to the brown wire (pin 3)
      • if fuel gauge moves then the cluster is good and the sender is bad


      I though I might be able to get away with just cleaning the sender in the hopes that the resister strip was just dirty, but no such luck. After inspection the part I found a break in the wire that connects to the float arm. You can see it if you follow the black wire past where it is soldered, right before it starts to spiral. I am really tempted to just try to heat the solder up and poke the wire back in, but I don't know if it's worth the hassle. I'm thinking it might not even work since it might mess up the resistance values. Plus there's the fact of me not wanting to start a fire by having a hot soldering iron near the open gas tank


    7. Member briano1234's Avatar
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      05-03-2014 06:50 PM #7
      Quote Originally Posted by tdubs329 View Post

      Cold solder joints are a pain.
      Clean the wire with sand paper.
      Get your iron really hot and if you have a solder sucker, get the old off, and use new.

      I had that same issue on a 67 MG that I had.
      Similar to the flakey water gauge fix.

    8. Junior Member
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      1999 Cabrio, 2002 Mustang
      05-04-2014 08:30 PM #8
      When I was out there yesterday with the sender taken out I uncoiled one loop of the wire on the arm and made hooks on each end of the broken wire and connected them back together that way. When I started the car yesterday for a second I didn't get a reading. But, I went out today and as I was pulling out of my parking lot the needle went up to half a tank!!! I went and filled the tank and the gauge is showing a full tank!!! Now I'm just crossing my fingers that it reads accuratly. I REALLY don't want to drop $300 on a new sender and pump

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