Oil & Fuel Fuel gauge pessimism

[PM1]

The fuel gauge on my 5203 always gives a pessimistic reading about how much fuel is in the tank. When I fill the tank, the gauge shows only 3/4 full. When the gauge first shows Empty, I have about 6 gallons left in the tank.

This obviously isn't a major issue, but it does mean I'm often operating with the gauge on Empty, hoping I have sufficient fuel left.

Is there a simple adjustment or fix that might correct this? Thanks.

 

[mfreund]

I ahve a 4310 and has the same problem. I reached into the tank and pulled on the float and all the way up it read 3/4 full so that told me the problem was in the guage and I have never priced an guage cluster. I was hopeful it was the sender as that is cheaper.

 

[Karl2]

Gentlemen, welcome to the growing membership of the John Deere Faulty Fuel Gauge Club

As the interior of my tractor cab lies sprawled in multiple pieces in front of the garage I figured I would make yet another attempt at troubleshooting this widespread issue and perhaps give something back to the JD operators community here assembled from which I have taken so much in the past few months.

I thought I had made progress by finding a fuel sensor on the parts lists of my 4720 but once I opened the exploded view of the fuel system where the sensor was supposed to be located it had vanished from the surface of the planet. I mean, among the 60 or so fuel system parts listed below the diagram not a single one was labeled a sensor. I thought maybe they had exploded the sensor itself into separate parts as well but couldn't find anything that looked like it could be part of a fuel level sensing device. No float, no electronic "eye", no stick of any sort inside the tank, no fuel flow guesstimator, no scale system to weigh fuel (a long shot but I was running out of ideas).

"This is odd" I thought, "perhaps it's a computer thing." And then an ominous theory started to take root in the back of my little brain. What if one of my tractor's computers was bugged? What if on these tractors the fuel level was simply computed based on rpm vs hours and the gauge on those tractors lucky enough to have a functional one was simply displaying a guesstimate? After all, late-generation jetliners have such systems, right?

Right, but we're dealing with a compact tractor here not a Boeing Airbus A380B787. And the computer has to have a way of knowing when the tank is full in order to compute anything so where is that friggin' sensor so that we can at least check if it's working or not?

 

[xlr82v2]

I believe your understanding of aircraft fuel quantity display systems is a bit flawed.

 

[sunnyside360]

PM1, my 4320 behaves exactly as yours. The sensor was replaced when it had less than 25 hrs and still is not right. I mentioned it to the dealer and he found a Tech Notice from John Deere which called for programming the computer to match the sending unit. He will check it out and hopefully fix it when they get the tractor for installing the new backhoe.

 

[Karl2]

I believe your understanding of aircraft fuel quantity display systems is a bit flawed.

My understanding of it ins't but I'll admit my describing was. Why bother with minor details like triple redundancy mechanical fuel probes and such

But it was for the purpose of demonstrating how the frustration of troubleshooting a seemingly simple problem can drive one to conceive of the "ill advisedness" of design overreliance on the computerization of basic but essential instruments on utility machinery. The latest theory to navigate the right side of my brain was that some sort of miniaturized mass spectrometer technology is perhaps being used to separate fumes residue into their various chemical constituents the proportion of which is known to vary according to volume and then feed the result to the computer for it to translate this data into something as basic as how much fuel is left in the tank.

This may seem far-fetched but the absence of any mechanical fuel probe in the tank and the fact that onboard computers on tractors are often designed in countries which don't seem to have the equivalent of the word "simple" in their vocabulary can drive one to conjure up pretty elaborate alternative theories.

Even though there is a "fuel sensor" listed in the parts list along with other fuel tank parts this part does not appear on the fuel tank apparatus diagram even though every other part listed along the sensor does appear. Moreover a "fuel sensor" is not necessarily a fuel *level* sensor, it can simply be a device that detects fuel flow to the engine. That's hard to tell if it's left out of the parts diagram through.

In the absence of any mechanical fuel level probe in the tank one can reasonably assume there must be an electronic device of some sort to fill this function. Logically this part should be listed with the electrical parts of the tractor itself, or that of the instrument cluster which is not made by JD and therefore likely not documented by JD either and that's why they apparently replace the whole cluster when something goes wrong with it and it's still under warranty. I couldn't find who makes this device by googling so I guess my next step is to pull it out and see if there is manufacturer info that can be obtained from visual inspection and pray that technical documentation in English exists.

My tractor is a winter machine so I figure have a reasonable chance at getting to the bottom of this before it gets too cold I hope. If I can't fix the fuel gauging problem I'll probably just buy some third party probing system

 

[Karl2]

PM1, my 4320 behaves exactly as yours. The sensor was replaced when it had less than 25 hrs and still is not right. I mentioned it to the dealer and he found a Tech Notice from John Deere which called for programming the computer to match the sending unit. He will check it out and hopefully fix it when they get the tractor for installing the new backhoe.

I had this done last February but it only caused the gauge to malfunction differently by remaining stuck on 1/4 tank. It has since reversed to its "normal" malfunction of indicating empty regardless of actual level so I use a "dipstick" made from a piece of old coaxial cable. Due to the tank's odd shape the dipstick has to be rigid yet flexible.

 

[xlr82v2]

I had this done last February but it only caused the gauge to malfunction differently by remaining stuck on 1/4 tank. It has since reversed to its "normal" malfunction of indicating empty regardless of actual level so I use a "dipstick" made from a piece of old coaxial cable. Due to the tank's odd shape the dipstick has to be rigid yet flexible.

I just can't help but get a chuckle from this... (thinking of airplanes...)

Your fuel guage is of acceptable accuracy to the FAA, which says that the fuel guage must only be accurate when the tank is empty...

(Yes, that's the truth!) As long as the display reads empty when the tank is actually empty, that's good enough!

 

[Karl2]

I just can't help but get a chuckle from this... (thinking of airplanes...)

Your fuel guage is of acceptable accuracy to the FAA, which says that the fuel guage must only be accurate when the tank is empty...

(Yes, that's the truth!) As long as the display reads empty when the tank is actually empty, that's good enough!

Ha! Then I can tell state inspectors to get off my case because my tractor meets FAA standards

 

[Spudland_Dave]

but the absence of any mechanical fuel probe in the tank and the fact that onboard computers on tractors are often designed in countries which don't seem to have the equivalent of the word "simple" in their vocabulary can drive one to conjure up pretty elaborate alternative theories.

Even though there is a "fuel sensor" listed in the parts list along with other fuel tank parts this part does not appear on the fuel tank apparatus diagram even though every other part listed along the sensor does appear. Moreover a "fuel sensor" is not necessarily a fuel *level* sensor, it can simply be a device that detects fuel flow to the engine. That's hard to tell if it's left out of the parts diagram through.

Maybe only the 4x20 uses the computational calculations? LOL...Found the sending unit for the 3x20 series cabbed machines...and I'm 99% sure its the same on your 4x20... Part #2: