[paulellis]

I need anyone's suggestion on what to do about my John Deere 5210 fuel gauge. It has been working fine forever but now all of a sudden it never gets past slam empty. Even at half full or slam full it never leaves the empty side. Any suggestions?
I will eventually take it to the dealer I just wanted to find out first if this had happened to anyone else first.

 

[56FordGuy]

Odds are either the gauge itself has failed or the sending unit has. Can you look in the tank and see for sure that the float arm is attached to the sending unit? I've seen them break off before.

If you have an ohm meter, you can test the sending unit and wiring yourself. Disconnect the plug on the sending unit and test the resistance across the pins. If you do this with the fuel level low enough, you can reach in and use a wire or coat hanger to move the float in the tank. The resistance should change as the float moves. If it does not, or is open then you have a bad sending unit.

If the sending unit checks out, the next step is to ohm out your wiring from the sending unit to the gauge. Disconnect both connectors and check it with your ohm meter. Resistance should be very low, with your gauge never moving off empty you may have a broken wire.

 

[paulellis]

Odds are either the gauge itself has failed or the sending unit has. Can you look in the tank and see for sure that the float arm is attached to the sending unit? I've seen them break off before.

If you have an ohm meter, you can test the sending unit and wiring yourself. Disconnect the plug on the sending unit and test the resistance across the pins. If you do this with the fuel level low enough, you can reach in and use a wire or coat hanger to move the float in the tank. The resistance should change as the float moves. If it does not, or is open then you have a bad sending unit.

If the sending unit checks out, the next step is to ohm out your wiring from the sending unit to the gauge. Disconnect both connectors and check it with your ohm meter. Resistance should be very low, with your gauge never moving off empty you may have a broken wire.

You know, when I peek inside the fuel tank, the part inside is sitting on top of the fuel. So when I took a coat hangar and tried to push it down it instantly bounces right to the top of the level of the fuel. Weird???

 

[56FordGuy]

That arm should be connected to the sending unit on one end. The other end should float at the top of the fuel. That's what the sending unit uses to tell how much is in the tank. When you push down on the arm, does the gauge do anything?

If the arm is there and floating (sounds like it is) then you'll need an ohm meter to continue troubleshooting; unless you get lucky and find something unplugged.

 

[jd5210]

Must likely your problem is the sending unit located in the tank. After sitting at least 13 years in diesel fuel it gave out. To rule out that it is not the wiring to the gauge or the gauge, key off, move the seat forward all the way, put a towel down in case you drop the nuts. Remove the two wires; a black and orange wire, there should be 353 on the orange wire. Turn the key to run (no need to start) touch the two wires together, the gauge should go to full. If not the gauge or wiring is the problem. If the gauge goes to full the problem is the sender.

If you want to test the sending unit the ohm range is 4.5 to 97.5 ohms. Double check JDparts.com, the fuel sender is part number RE190977. From JD it is $56.00. Replace with less than a half tank of fuel. It also helps to put some sealer on the gasket to keep it from leaking.

What you are seeing in the tank that bounced up is the float. You can do a google search if you want to see what it looks like.