Fuel sending unit ohm info

[aaluck]

Just for info purposes, as I know this is a common tractor problem and I searched the internet for this information for weeks and couldn't find it.

I have a L4400 (so not sure if this will apply to all tractors) but MY fuel sending unit reads 0 ohms at FULL and 120 ohms at EMPTY. NOW IT APPEARS THAT THE UNITS ARE USUALLY 0-90 SO THAT MAY BE THE BEST FIT, AS I DO NOT SEE UNITS IN THE 0-120 RANGE. There are plenty of generic units out there that will do the same as the OEM part at a tenth of the price.

 

[Roadworthy]

Thanks for sharing that tidbit of information. Perhaps the difference in range is why genuine Kubota units are worth the big bucks. It could be a specialty thing.

 

[aaluck]

No problem. Probably right on the difference between generic and OEM. However, the generic ones are about $15-$20 on Amz and the OEM is about $98. The generic one will read empty probably around with an eighth of a tank.

 

[AllDodge]

The range is interesting, because it gives it very little change for resolution. North American standard for boats is 240 (empty) to 33 (full) ohms. Same range is used for temp gauge as well.

Many automotive older style also used the same range.

 

[aaluck]

I agree. In fact the one I purchased on Amazon (Bosch) had the ranges of "Empty - 240 ohms; 1/2 - 130 ohms; Full - 33 ohm", which seems to be standard. I hooked it up outside the tank and moved the arm up and down...with the arm in the FULL position the gauge showed about half way between empty and one-half full.

I did carefully, and several times, measure the OEM one it it was clearly 0 at FULL and consistently between 110-120 on EMPTY.

Anyway, I'm not sure why my OEM one doesn't work inside the tank. Outside the tank it functions fine and once I put it in it stays at FULL, so I'm going back to my stick.

 

[Roadworthy]

You may wish to check your sender a bit further. There may be something binding or your float may have a leak.

 

[aaluck]

It is very strange! I can take a stick and actually push the float down while installed in the tank and watch it go down. Let go.... it goes back up. I'm starting to think that it is working but doesn't move until about one-half a tank is gone.

Right now I'm at about 3-4 of a tank and it is still reading full and the float is at the top of the gas. If i take the stick and push the float down the gauge follows...let the stick out it jumps back to over full--even with only 3-4 of a tank.

I usually keep a full tank but Im going to let it run down and see if it ever moves, or if I push it down it stays there.

 

[sdkidaho]

I'll try the stick method and see if I can get it to move and I'll check out the ohms as well. I can probably check continuity as well.

 

[aaluck]

Thanks. Please let me know

 

[Fordtech86]

It is very strange! I can take a stick and actually push the float down while installed in the tank and watch it go down. Let go.... it goes back up. I'm starting to think that it is working but doesn't move until about one-half a tank is gone.

Right now I'm at about 3-4 of a tank and it is still reading full and the float is at the top of the gas. If i take the stick and push the float down the gauge follows...let the stick out it jumps back to over full--even with only 3-4 of a tank.

I usually keep a full tank but Im going to let it run down and see if it ever moves, or if I push it down it stays there.

When i got my tractor i thought the fuel gauge didn’t work either. Stayed on full forever. It seems that the level doesn’t really start dropping on the gauge until around 1/2-2/3 of a tank. Maybe due to tank shape and location of the sender? I never really looked into it.

 

[aaluck]

When i got my tractor i thought the fuel gauge didn’t work either. Stayed on full forever. It seems that the level doesn’t really start dropping on the gauge until around 1/2-2/3 of a tank. Maybe due to tank shape and location of the sender? I never really looked into it.

Thats exactly what I discovered. It turns out it was working properly, but since I would usually just top-it-off it stayed on full.

I decided to run it for a while before filling and sure enough, it started going down.

 

[rogerwh0825]

My BX is pretty much the same. Per the gauge I get about double the run time from full to 1/2 tank vs 1/2 to near empty.

 

[CallMeChaz]

The wiper that travels across the resister on mine had lost it's spring tension and was only reading about 1/2 the length of the resister before losing contact. Only read part of the tank then stopped. I pulled the cover off and bent the wiper back down. Works fine now.