Gas gauge..

[70c10guy]

Another gas gauge thread.. I've looked but all the answers I seem to find aren't clear. My gas gauge has been working fine and my sending unit also has an updated float. The jeep float! I was driving today and all of a sudden it got stuck on 1/8th of a tank... I filled up and still not movement. How do I go about testing of its the sending unit or the gauge itself? Can the gauge itself even go bad?
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[TBONE1964]

Originally Posted by 70c10guy

Another gas gauge thread.. I've looked but all the answers I seem to find aren't clear. My gas gauge has been working fine and my sending unit also has an updated float. The jeep float! I was driving today and all of a sudden it got stuck on 1/8th of a tank... I filled up and still not movement. How do I go about testing of its the sending unit or the gauge itself? Can the gauge itself even go bad?
Posted via Mobile Device

The first thing you want to do is pull either the ground or the sender (tan) wire from the sending unit and watch the gauge with the key in the on position. The gauge should move all the way to the 3 o-clock position. If it does, the gauge is OK

The next thing to do is check the ohm reading on the sending unit. When the tank is empty you should have zero or close to zero ohms. With a full tank it will be about 90 ohms. A half tank will be around 45 ohms, you get the idea. You can do this test with a friend at the gas station. Remove the sender wire from the sending unit, use your ohm meter and probe the terminal on the sending unit and the other to a ground. Watch the action of the ohm meter as you fill the tank. It should have a steady increase from zero to 80 ohms as the tank fills. If it does not, then you should look into replacing the sending unit.

You can also pull the sending unit out and do a bench test and just sweep the float. At 1/8 tank you should read around 11.5 ohms. If you do the sweep or you are filling the tank and your ohm reading stops at 11.5 or close to that, then your sending unit is the problem.

You may also have a bad resistor at the gauge. Typical when a resistor on the gauge goes bad, you will get up to a 1/4 tank and no more. The ohm reading across the resistor should be some where between 85 - 100 ohms. They do vary in resistance some but that has very little effect on the gauge reading.

Typically the gauge itself does not go bad and if it does, it will not move at all.

If you still have problems contact board member VetteVet. He is a master on electrical issues on our trucks.

Hope this helps,

Take care,
Tom

[70c10guy]

Thanks tbone. That helped me a lot. Today... When I started the truck up, the gauge shot right up to full. So this problem is being intermittent. It was about at 3/4 tank by the end of today but it's just stuck there now.. I'm thinking it's the gauge resistor. Do you agree? Can I replace just the resistor?

[TBONE1964]

Originally Posted by 70c10guy

Thanks tbone. That helped me a lot. Today... When I started the truck up, the gauge shot right up to full. So this problem is being intermittent. It was about at 3/4 tank by the end of today but it's just stuck there now.. I'm thinking it's the gauge resistor. Do you agree? Can I replace just the resistor?

Typically if the resistor is the problem, the gauge will not move past 1/4 tank no matter what the fuel level is. If you are showing anything over 1/4 tank, then I would bet the gauge itself and resistor are OK. Double check all of the connections. Bad connections are the number one reason for intermittent problems.

You should do an ohm reading on the sending unit and see if it corresponds to the amount of fuel showing on the gauge. You may want to pull it from the tank and get a good look at it and make sure it is not wore out. It is also easy to do repetitive sweeps of the float arm with the ohm meter hooked up.

Let me know what you find out,

Take care,
Tom