ZD1211 Fuel Tank Equalization

[RjCorazza]

Anyone understand how the left / right fuel tank equalization works, and how the fuel is gets to the engine?
My previous understanding was that the pipe across the top of the tanks carried fuel from left to right, with the engine always drawing off of the right tank. From the parts diagram it would appear that fuel is drawn equally from both tanks, with a plain "T" fitting between the 2 tank filters.
Does the fuel actually equalize through the top connecting pipe, or does this simply vent between the tanks to keep the pressure the same?

What prompts my question is that after 575 hours fuel is now only being used up from the right tank, with the left tank remaining full. Both tank valves are open. I turned the fuel valve off from the right tank, and the mower will operate fine while drawing only from the left tank.
My next step is to replace the 2 filters thinking perhaps the left filter is more clogged than the right, causing fuel to take the path of least resistance. Thoughts?

 

[jcummins]

Trash in the tank that's not being drawn from and it's blocking the pickup.

 

[WM75Guy]

If I remember correctly the gauge only shows the right tank. Mine draws from both tanks about equally but they don't equalize. I have run the left tank dry. When I was using 5 gallon cans to fill up I always made sure the right had the most fuel. Now that I have a 58 gallon diesel storage tank to fill it that shouldn't be a problem.

 

[RickB]

They don't equalize well. Everything has to be perfect for the tanks to draw evenly. Guidance from Kubota is to draw from one tank then the other. This works best if you draw from the right tank and switch off before it reaches E then use the left tank. I guess they figure the grass will be cut before the second tank runs out. The upper hose only serves to keep both tanks equally vented.

If I owned one I would eliminate the filters from each tank and run a single filter between the tee and engine.

 

[RjCorazza]

They don't equalize well. Everything has to be perfect for the tanks to draw evenly. Guidance from Kubota is to draw from one tank then the other. This works best if you draw from the right tank and switch off before it reaches E then use the left tank. I guess they figure the grass will be cut before the second tank runs out. The upper hose only serves to keep both tanks equally vented.

If I owned one I would eliminate the filters from each tank and run a single filter between the tee and engine.

It would imagine that one filter after the tee would ensure that each tank is more equally being drawn from. I replaced the first inline filter on my previous zd331 and current zd326 backup mower with a large 2 micron Cat filter that worked very well.

 

[Brown Dog]

I noticed one of my ZD1511 mowers seems to accept more fuel in the right tank at fill up’s where it use to be more evenly.

 

[Bigkrank]

Had to replace the fuel filters on my 1211 at 106 hours due to it not sucking fuel out of one tank. Been even ever since.

 

[Hay Dude]

Be happy you have that feature.
One of the very few criticisms I have of my ZD331 is the tanks require manual switch over and the audible alarm doesn’t sound when one tank is low. She has died on me on a steep hill more than once.
Moral of the story: make sure your tank is pretty full, or remember to switchover to more full tank before you cut a hill on the older twin tank models.

 

[jcummins]

Be happy you have that feature.
One of the very few criticisms I have of my ZD331 is the tanks require manual switch over and the audible alarm doesn’t sound when one tank is low. She has died on me on a steep hill more than once.
Moral of the story: make sure your tank is pretty full, or remember to switchover to more full tank before you cut a hill on the older twin tank models.

Had ZD326.. I T'd the tanks together, eliminated switch. Gage then showed TOTAL fuel, idiot light I blocked since it always came on when the gage showed 1/2 tank left. Worked so much better.

 

[RjCorazza]

Follow up...
Replacing the tank fuel filters fixed the uneven fuel draw problem. I did discover that these 2 filters are larger than the filters I'm used to on the zd326 and zd331.
Also, there are check valves on each tank line at the filters, so the engine must only draw somewhat equally on both tanks, with no other type of equalization.