Bobcat T300 fuel gauge not working

[PhilB]

Need some help here guys.
T300 Bobcat fuel gauge reads full all the time. Haven't really checked anything yet but I've always assumed it was in the control panel. Just recently thought that it could possibly be in the sending unit. Makes work difficult when you don't know when you're going to run out of fuel in the middle of a project or right before you're finished. Anyone have any experience with this and suggestions as to where I might start troubleshooting?

 

[brdgbldr]

Need some help here guys.
T300 Bobcat fuel gauge reads full all the time. Haven't really checked anything yet but I've always assumed it was in the control panel. Just recently thought that it could possibly be in the sending unit. Makes work difficult when you don't know when you're going to run out of fuel in the middle of a project or right before you're finished. Anyone have any experience with this and suggestions as to where I might start troubleshooting?

I would change out the fuel sending unit. Not an easy job because of the location.

Mine had split and so it was either full or empty, no in-between.

On my A300 I was able to barely reach it through the left side, top, access panel. Even then, it was partially under the pump and someone else had tried and messed up the top so I could not get a socket on it. Had to use wide mouth vice grips to unscrew it.

 

[fortworth-cowboy]

Need some help here guys.
T300 Bobcat fuel gauge reads full all the time. Haven't really checked anything yet but I've always assumed it was in the control panel. Just recently thought that it could possibly be in the sending unit. Makes work difficult when you don't know when you're going to run out of fuel in the middle of a project or right before you're finished. Anyone have any experience with this and suggestions as to where I might start troubleshooting?

If you lift your boom up and secure it with the lift arm support device, you can remove both side panels completely and reach with your arm in and unplug the unit. Socket for the fuel sending unit was, I think, a 42 mm

 

[ZekeSkyree]

Before swapping it out, there should be two wires going to the unit. Unplug one and see if the gauge changes. Then short then together and see if it changes. One should show full and the other empty.

 

[fortworth-cowboy]

Before swapping it out, there should be two wires going to the unit. Unplug one and see if the gauge changes. Then short then together and see if it changes. One should show full and the other empty.

That will throw a code, DO NOT THAT! What you could do, remove the fuel sending unit from the tank, plug it back in and move the plunger up and down while the machine is turned on ACC. Then you can see if the fuel gauge is moving or what is the problem. Possible that the plunger is stuck or the rod is bent--which would indicate an issue with the fuel tank.

 

[ZekeSkyree]

Cowboy, just a question on that model. Is it easy to reset codes? Since the gas sender is just a rheostat, it seems high/low testing would be a simple test. I've mostly older hardware (analog) and the test I suggested has helped me pinpoint a sender, gauge or wiring issues many times and I am wondering if it is not a good idea on the newer computer controlled models.

 

[fortworth-cowboy]

Cowboy, just a question on that model. Is it easy to reset codes? Since the gas sender is just a rheostat, it seems high/low testing would be a simple test. I've mostly older hardware (analog) and the test I suggested has helped me pinpoint a sender, gauge or wiring issues many times and I am wondering if it is not a good idea on the newer computer controlled models.

The ohm changes inside the sending unit, the controller measures the resistance and that is what shows the fuel level. If you just unplug a wire, it will throw a code, either fuel sending unit output high or low. But that does not diag the issue. What I usually always did, in the Bobcat Shop, I had an old but still good sending unit, unplugged the unit inside the machine and hooked my tester up to it. That way I was testing the wiring, the sending unit and the gauges.
I have to say, that by these old T300 the displays often also go out.
But without tester , I would remove the sending unit from the machine, leave it hooked up to the connector, turn the machine on ACC and watch the gauges while you move the swimmer up and down.
In the case of PhilB here i suspect that the fuel sending unit is bent, thats why the swimmer stays up and always shows full. Usually the swimmer falls apart or so and fills full with diesel and shows then always empty.

 

[ZekeSkyree]

The ohm changes inside the sending unit, the controller measures the resistance and that is what shows the fuel level. If you just unplug a wire, it will throw a code, either fuel sending unit output high or low. But that does not diag the issue. What I usually always did, in the Bobcat Shop, I had an old but still good sending unit, unplugged the unit inside the machine and hooked my tester up to it. That way I was testing the wiring, the sending unit and the gauges.
I have to say, that by these old T300 the displays often also go out.
But without tester , I would remove the sending unit from the machine, leave it hooked up to the connector, turn the machine on ACC and watch the gauges while you move the swimmer up and down.
In the case of PhilB here i suspect that the fuel sending unit is bent, thats why the swimmer stays up and always shows full. Usually the swimmer falls apart or so and fills full with diesel and shows then always empty.

Cowboy, Thanks for the info.