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Old 10-15-2010, 05:39 PM
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How to trouble shoot fuel guage.

Got a 1984 chevy truck. Fuel guage does not work. I put a new gas tank with a new sending unit, and it still does not work. I bought a new fuel guage and it did not work. Is there any simple way to trouble shoot, to find out if it is a ground problem, circuit board.. Tried a different sending unit to. The so called "mechanic "f who did the work finally said he did not no how to fix it.

Thanks Lee

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Old 10-15-2010, 06:22 PM
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does the gauge move? does it read anything?
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Old 10-15-2010, 06:35 PM
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It stays @ about a !/4 of a tank. If I run it completly out of gas it will go to about half a quarter. I fill it up. it goes to a quarter. Same thing with the new guauge. Move very little. With the engine off, it reads the same.
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Old 10-15-2010, 06:55 PM
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Start by, with key on, grounding the sender wire at tank. The gauge should read full. Unhook the wire, the gauge should read empty. This should let you know if the gauge can do the full sweep. Or if the gauge still gets stuck somewhere, there maybe too much resistance in some wiring or connector.
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Old 10-15-2010, 07:03 PM
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What he said.
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Old 10-15-2010, 07:14 PM
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U replaced with compatable parts? The parts must be of the same resistance. . Equal with each other.
30 ohms to 30 ohms or what ever.
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Old 10-15-2010, 09:02 PM
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Is the float properly adjusted? Almost sounds like it is stuck. Is the sending unit an OEM unit or is it a replacement/aftermarket?
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Old 10-15-2010, 10:52 PM
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I would do what rexnfx said first.
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Old 10-16-2010, 07:40 AM
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I think you may have a broke wire, if you have an ohm meter and can use that, it will tell you what is up.

Unplug the sender at the tank; turn on the ignition; take a voltage reading on the wire you disconnected; it should read 12 v; no voltage broken/cut wire . You also could use a test light to prove the same. fyi

The sender itself is noting more then a resistor; it divides the voltage to the gage; the fuller the tank the less resistance; the gage reads full

another item to mention; GM sender when empty reads 90 ohms .

With that in mind, you could connect the meter; one probe on the sender where the wire connects the other meter probe to the tank; if you have gas in there and it is reading 90 ohms the sender is the bad actor. With gas in the tank. lets say just for grins the tank is 1/2 full; you should expect a reading of about 45 ohms.

Last edited by pepi; 10-16-2010 at 07:50 AM.
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Old 10-16-2010, 08:22 AM
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DISREGARD the above; ran into a server limit and could not edit see the following; it has been corrected to more accurately reflect the symptoms described

Quote:
Originally Posted by Bracewell
It stays @ about a !/4 of a tank. If I run it completly out of gas it will go to about half a quarter. I fill it up. it goes to a quarter. Same thing with the new guauge. Move very little. With the engine off, it reads the same.
My money says you have a sender problem; could be the wrong one; GM sender when empty reads 90 ohms .

Two ways to tell; first the easiest; remove the wire from the sending unit; take a reading with an ohm meter with a low fuel level in the tank; if it reads more then 90 ohms it is the wrong sender.

second way to test; remove the sender; with it out of the tank and the float hanging free; as if empty see if it reads 90 ohms; as you raise the float; the meter will go to 0 ohms

If the empty reading is greater then 90 ohms you have the incorrect sending unit; You said you have replaced the sender? Did that come with the tank who is the manufacture ?

Also my information is based on the fuel gage being stock or GM specific; if it is a custom gage; no problem really it still comes down to a miss-match of the components; one or the other will need to be changed; be it the gage or the sender.
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Old 10-16-2010, 10:42 AM
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how to trouble shoot fuel gauge

I agree check with ohm meter you might have cut the float rod to short. you also sent you tried another sender when the new ones didn't work, if it wasn't the right one it wouldn't work.


35terraplane
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