Kubota fuel gauge stuck on full

SRS

New member

Equipment
Cabbed B3030, equipped with a FEL, FEL snow plow, belly mower, and forks.
Jan 3, 2010
28
0
0
Jarrettsville, Maryland
After 4 years of ownership and 270 hrs the fuel gauge on my B3030 HSDC is now stuck on full. I removed the dash to check for tightness of all wires, everything appears fine. I removed the sending unit and tested the float in a bucket of diesel fuel and it moves freely up and down. The weird part is when I removed the sending unit from the fuel tank and connected the two wires to it, one a ground and the other power it worked fine. I move the float up and the gauge goes to full, lower it and I can watch the gauge drop. Lower the float all the way the gauge goes to empty. I then reinstalled the sending unit in the fuel tank connecting the same wires in the same order but when I turn the key to on it goes right to full. Turn the key off it goes to empty.

I also removed the battery ground to check for corrosion but it was very clean.

I removed the power wire feeding the sending unit and touched it to the ground of the sending unit, gauge went to full.

I removed the ground wire from the sending unit, then attached a long piece of wire to the ground on the sending unit and then touched a æ¾±olt on the frame, still reads full.

I removed the sending unit and took the cover off. Everything looks like new, no broken parts.

Others have suggested an ohmmeter but even if I had one I would not know how to use it. I guess if it is imperative I have an ohmmeter to definitely figure out what is wrong I could get a cheap meter from Harbor Freight and learn/try to learn how to use it.

FYI I have approximately 1/2 tank or less of fuel.

Any suggestions? I thank you in advance. Stanley
 

GWD

Member

Equipment
M7040, L48 TLB, BX2200
Jan 8, 2010
792
12
18
Northern California
Lets see if I have this right.

1. Disassembled and in your hand the gauge works perfectly.

2. Installed in the tank the gauge reads either full (with power) or empty (with no power) and nothing else.

3. When the power wire is attached to the ground wire the gauge reads full.

The logical conclusion is that the positive terminal of the sending unit is grounding through the frame of the unit or through the tank material (if it is metal).

Check for cracks in the housing. This is where an ohmmeter is handy.

As far as an ohmmeter, Harbor Freight has a basic one for $3. It is also one of the "free" items with any purchase if you have the coupon. The instructions that come with it are not too bad.
 

SRS

New member

Equipment
Cabbed B3030, equipped with a FEL, FEL snow plow, belly mower, and forks.
Jan 3, 2010
28
0
0
Jarrettsville, Maryland
Lets see if I have this right.

1. Disassembled and in your hand the gauge works perfectly.

2. Installed in the tank the gauge reads either full (with power) or empty (with no power) and nothing else.

3. When the power wire is attached to the ground wire the gauge reads full.

The logical conclusion is that the positive terminal of the sending unit is grounding through the frame of the unit or through the tank material (if it is metal).

Check for cracks in the housing. This is where an ohmmeter is handy.

As far as an ohmmeter, Harbor Freight has a basic one for $3. It is also one of the "free" items with any purchase if you have the coupon. The instructions that come with it are not too bad.
GWD, thanks for the reply, what exactly do you mean when you say the positive terminal of the sending unit is grounding through the frame? And where exactly do I check for cracks? The tank is plastic also. I'll be going to HF next week sometime. Thanks again, Stanley
 

GWD

Member

Equipment
M7040, L48 TLB, BX2200
Jan 8, 2010
792
12
18
Northern California
You stated, "I removed the power wire feeding the sending unit and touched it to the ground of the sending unit, gauge went to full".

That means that, when the sender is installed, the power wire is shorting out to the ground wire. The power wire is somehow finding an electrical path with little or no resistance and is completing the circuit to the ground wire. (It is not really a "ground wire" - it likely is attached to your fuel gauge. When you get the ohmmeter you can set it for volts and find out which wire is power.)

If you can imagine a rheostat that is attached to your fuel float then the up and down motion of the fuel float turns the rheostat to allow more (or less) current to flow through it and to the fuel gauge. (A rheostat basically allows a variable amount of current to run to a device.)

Rheostat: http://en.wikipedia.org/wiki/Potentiometer

With an ohmmeter you can measure the resistance along the rheostat to find out if it is working or not. It seems to be working in your hand. Perhaps installed in the tractor the angles are not the same and it is not making proper contact or is shorting out.

If you do get an ohmmeter then test the sender out of the tractor. Touch one of the leads to power and the other lead to the ground terminal (doesn't matter which way - red or black). Note the ohms when the float is in different positions, empty to full positions and a few along the way. Write the readings down.

Then install the sender and use the ohmmeter and check the ohms (tractor off). If it reads one of the "part way" numbers then it is working properly. If it reads the "full" reading then the sender is defective when installed or the float is stuck at the top of its motion.

You might try buying a new sending unit. A new unit should work well given the information that you have provided.
 
Last edited:

SRS

New member

Equipment
Cabbed B3030, equipped with a FEL, FEL snow plow, belly mower, and forks.
Jan 3, 2010
28
0
0
Jarrettsville, Maryland
Again thank you. When I took the sending unit out I opened it up (small metal cover plate) everything looked perfect, no broken wires, moves freely, etc. I'll let you know next week some time after I purchase the ohm meter.
 

SRS

New member

Equipment
Cabbed B3030, equipped with a FEL, FEL snow plow, belly mower, and forks.
Jan 3, 2010
28
0
0
Jarrettsville, Maryland
Fuel gauge problem fixed. Apparently the float somehow got stuck in the 'full' position. I decided to drain the tank, turned the key to on and the gauge read empty. I kept the key on and refilled what I had removed and as I was refueling the gauge slowly went from empty to a little over half full. Turned the key off gauge dropped to empty, turn the key back on, gauge moved upward. Phew!!!! Thanks everyone for their advise and suggestions. Stanley
 

GWD

Member

Equipment
M7040, L48 TLB, BX2200
Jan 8, 2010
792
12
18
Northern California
Thanks for posting back on the solution.

Sometimes the most simple approach is the best. That is, work from the simple fix to the most complex fix in ever increasing steps.

All's well that ends well. (Didn't just make that up.;) )
 

SRS

New member

Equipment
Cabbed B3030, equipped with a FEL, FEL snow plow, belly mower, and forks.
Jan 3, 2010
28
0
0
Jarrettsville, Maryland
This problem drove me crazy but it got fixed which is the bottom line! But I think next time I go to fill the fuel tank I may not fill it completely to the top like I've done in the past. Thank you for your help! Stanley
 

sdkidaho

New member

Equipment
B3030
Oct 22, 2019
6
0
0
Rigby, Idaho, United States
So it's 7 years later from when this thread was started but I've got a similar problem.

My gauge says empty instead of full.

How do I get the sending unit or float or whatever it is out to check it? I'm not a mechanically inclined guy but I'm not totally inept either. If there is a manual that shows this, or youtube video or something I could probably get it done.

Thanks for your help.
 

aaluck

Well-known member

Equipment
L4400HST, Bush Hog 276, RDTH60, Speeco PHD, etc
Oct 9, 2019
927
743
93
Snowdoun, AL
No manual, nothing.

Ive been dealing with this and actually have an active post on the same issue. Here is what Ill tell you...

The float runs L to R (float probably on right side) while sitting on the tractor and probably in the rear of the tank. Get a stick, start it up and push, or pick up the float with said stick. If the gauge works your problem is the float.

You can double check this by disconnecting the wires from the sending unit. Once disconnected the gauge should drop to empty. Touch the two wires together and it should jump to FULL. If that works find my OHM post on how to order a generic sending unit.

At this point you know what the problem actually is...I'm betting the float is stuck or sending unit bad.