# Have a fuel tank plumbing issue.



## Country Boy (Mar 18, 2010)

I have a Derby ZT2354 zero turn mower in the shop here that we converted to a Kohler EFI engine. My problem is that, with the tanks hooked up the way Kohler recommended, the one tank runs out of fuel before the other and then the engine dies because it is sucking air from that tank instead of fuel from the other. The way Kohler said to hook it up was to install a T between the tanks and then draw off that T. They said not to have a shutoff between the tanks because it would cause one tank to overfill due to the return line from the pressure regulator dumping into one of the two tanks. This does not appear to work.

I am contemplating a few different ideas on how to fix this. I can pick up a fuel tank selector valve from Ariens/Gravely that will reroute the fuel draw and the fuel return lines to one tank or another, however, that will cost $73 just for the valve. My other thought was to install a 5/16" or larger fuel line between the two tanks as an equalizer line, but I am not sure if that will keep up with the pump. I could also tee off the fuel return line and run that to both tanks but there would be no way to regulate how much fuel goes to each tank that way. The last option I can think of is to just run one tank, however the customer would prefer to use both. Any ideas?


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## dangeroustoys56 (Jul 26, 2010)

The T should be the lowest point in the system- then it would draw from both tanks equally.

An alternative to the expensive selector switch is get one at an auto junkyard from a dual tank pickup truck - the solenoid and switch shouldnt be that much together.


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## Country Boy (Mar 18, 2010)

The T is currently at the low point, however because the return line is being dumped into one tank only (per Kohler's instructions), and the pump runs constantly, the one tank empties and the other fills. The two tanks are connected via the fuel lines at the T and do balance over time after the engine is shut off, but the current system can't keep up balancing the levels in the tanks when the pump is running. I had thought to put a 5/16" fuel line directly from the bottom of one tank to the bottom of the other simply to balance the levels, but I don't know if that will keep up and I don't want to start drilling all sorts of holes in the tanks if I don't have to. The other thing I had thought of was to T the return line and have it dump into both tanks, but I am not sure if it will be equal. I'd have to make sure that the lines were even in length so there was equal resistance, but that would be the easiest route to go. I was just hoping to get an outside opinion on this as I have been working with this unit for the last month and a half and its getting tiring running into one problem after the other.


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## jhngardner367 (Apr 5, 2011)

I think the split-return would be the best bet,CB.Neither tank will overfill,and as long as the two lines are equal in diameter,and length,it should be fine.Unless the pump is returning MORE fuel than it is feeding,it can't overfill either tank.


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## Country Boy (Mar 18, 2010)

I think that would be the best too, now that I think of it. It only involves drilling one more hole, and about 2' of fuel line and a fitting. I'm trying to save the guy as much money as possible because we already have almost $1200 into the unit with all the parts we had to buy for it. The computer ended up being burned out, so after scratching my head for a week on it, I called the tech guys at our distributor, and they said to try everything I had just tried. They figured that the computer was junk, so I ordered a new one, plugged it in, and it fired right up. I was the happiest guy in the world right then to hear that baby purr. Then I tried to mow with it, and after a few minutes, the engine started sputtering and wanting to die. It gave me a code 31, which is lean running, and that's when I found out that the one tank was completely empty and it was sucking air. I let it sit a few minutes, and it fired right back up and ran like a top again until the tank was empty. I just want this thing out of my shop so I can get to the half dozen other tractors and ZT's up in the shed. This thing is monstrous and it takes up a good portion of my shop. It has a 54" deck, but the chassis is almost that wide as well.


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## JerryForrester (Jul 25, 2011)

Can you run a 3/8" line between the tanks and do away with the tee and pull the fuel from only one tank?
Jerry


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## Country Boy (Mar 18, 2010)

Jerry, that's a good suggestion, and something I hadn't though of. Dump the return into the left tank, connect the two and pull from the right. Might try that next time. I ended up splitting the return line to the two tanks and had to change the suction line on both tanks. The one line was 30" and the other was about 50". Splitting the returns made a big difference, but I had to add those 20" to the one fuel line and loop it so I could get an even draw from the tanks. I thought the draw lines were about the same length until I stuck my head in there and found out the one routed way forward of where I thought it did. It seemed pretty even when I had it running outside for over a half hour this time, and I mentioned it to the guy to keep an eye on it so he can either adjust the pickup line length or have me do it if necessary. I am quite impressed with that engine. It idles smooth as glass, accelerates like a two cycle and is very quiet.


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## Mickey (Aug 14, 2010)

One thing that comes to mind after reading your second comment CB. Have you checked to see if the tank vent on the tank that doesn't empty is open? If tank vent is plugged partially or completely, gravity can't do its job of keeping both tanks level, fuel wise. You also might want to check to make sure the supply line on the tank that is not emptying is completely open as well.


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## Country Boy (Mar 18, 2010)

I did blow out the tank outlet after equalizing all the hoses didn't seem to fully work. That seemed to take care of any remaining problems.


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