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I have a 1989 Chevrolett C3500. The fuel gauge started acting up, when the truck was full of fuel it would only read 1/4 of a tank and empty would read empty. I put the truck in the shop with a local mechanic for a bad fuel pump and told him to fix the fuel gauge as well. He installed a new fuel pump and sending unit. Now the fuel guage read full when the truck it full of fuel and 3/4 when the truck is totally out of fuel. The mechanic says there is nothing wrong with the guage or the new sending unit. any suggestions.

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  • Jamie Alton
    Jamie Alton Nov 05, 2012

    I would presume that the fuel sender unit is still at fault. Is it possible that this particular sender unit can be installed the wrong way around? The only style sender units have to be fitted at a particular angle.Your mechanic should check the operation of the sender unit before fitting it into the tank. If he had done this with it connected to the vehicle's wiring and operating by hand while watching the instrument panel gauge, then he should already know if both the gauge and sender unit were operable.If he had performed this check, then he would have had two results:1) The sender unit was faulty, or the gauge was faulty.2) Neither were faulty. But in this scenario he wouldn't have needed to use so many parts and would have informed you of the situation before you had to find out for yourself.So the simple basics of it I suspect is that your mechanic hasn't done a good job of diagnosing the issue, before carrying out the repair. I admit that not all issues of all types can easily be diagnosed without first changing parts, but in this case it would be relatively simple.Even if the vehicle's gauge is faulty, he could run a resistance check on the original sender unit with a multimeter.If the sender unit was fine, then that should have led him to the dash dial. If he had replaced that and worked the sender unit by hand, then he would know if he had fixed the issue.Take your car back to him and ask him to check everything again. You can write down my methods and tell him how to check the operation of the sender unit again.I'll repeat:1) Take out the sender unit from the fuel tank, taking note of the angle it comes out at. If the float angle or arm of the sender unit is misaligned, then this will offer a false reading, in which case, re-align the sender unit.2) With the unit removed from the tank, but still connected to the vehicle's wiring, and any electrical fuel pump DISCONNECTED (IMPORTANT SAFETY NOTE), turn on the vehicle ignition. Let the gauge drop to its lowest point by allowing the sender unit float to drop to its lowest point. In slow increments raise the float manually by hand and do a visual check on the dash fuel dial. Is it operating correctly as you manually move the seder unit float upwards and then back down again?If the gauge is erratic, or isn't registering anything, then check the gauge dial and replace.After carrying out those procedures, you should already have discovered where the fault was. If not, then please repost.Good luck!

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  • Cars & Trucks Master
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I would presume that the fuel sender unit is still at fault. Is it possible that this particular sender unit can be installed the wrong way around? The only style sender units have to be fitted at a particular angle.Your mechanic should check the operation of the sender unit before fitting it into the tank. If he had done this with it connected to the vehicle's wiring and operating by hand while watching the instrument panel gauge, then he should already know if both the gauge and sender unit were operable.If he had performed this check, then he would have had two results:1) The sender unit was faulty, or the gauge was faulty.2) Neither were faulty. But in this scenario he wouldn't have needed to use so many parts and would have informed you of the situation before you had to find out for yourself.So the simple basics of it I suspect is that your mechanic hasn't done a good job of diagnosing the issue, before carrying out the repair. I admit that not all issues of all types can easily be diagnosed without first changing parts, but in this case it would be relatively simple.Even if the vehicle's gauge is faulty, he could run a resistance check on the original sender unit with a multimeter.If the sender unit was fine, then that should have led him to the dash dial. If he had replaced that and worked the sender unit by hand, then he would know if he had fixed the issue.Take your car back to him and ask him to check everything again. You can write down my methods and tell him how to check the operation of the sender unit again.I'll repeat:1) Take out the sender unit from the fuel tank, taking note of the angle it comes out at. If the float angle or arm of the sender unit is misaligned, then this will offer a false reading, in which case, re-align the sender unit.2) With the unit removed from the tank, but still connected to the vehicle's wiring, and any electrical fuel pump DISCONNECTED (IMPORTANT SAFETY NOTE), turn on the vehicle ignition. Let the gauge drop to its lowest point by allowing the sender unit float to drop to its lowest point. In slow increments raise the float manually by hand and do a visual check on the dash fuel dial. Is it operating correctly as you manually move the seder unit float upwards and then back down again?If the gauge is erratic, or isn't registering anything, then check the gauge dial and replace.After carrying out those procedures, you should already have discovered where the fault was. If not, then please repost.Good luck!

Posted on Nov 05, 2012

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  • Cars & Trucks Master
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I think the sending unit was damaged on installation or is defective. Did you use a factory OEM part.

Posted on Nov 05, 2012

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SOURCE: 2001 hyundai sonata 4 cl can't pump fuel into tank @ normal rate

The sending unit in your tank is going bad replace it.

Posted on Jul 10, 2009

roniecon
  • 6927 Answers

SOURCE: fuel guage was erratic then went past full

Test the gauge by using a test light ,and grounding the test light clip to a good known ground,then touch the pink wire on the connector harness going to the tank,with the connector unplugged,and key on,the gauge will move slowly to the empty mark,and lower ,then remove the test light and it will go past full,if it does this,it is a good gauge,and the sending unit,was put in wrong,or the part was bad.

Posted on Apr 28, 2010

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