What's best way to clean fuel tank?

[HCJtractor]

My kubota M 6800 randomly starts chugging and then shuts off. I go thru the bleeding air process and it fires right up again and runs fine until the next time. I have removed both tanks and plan to replace all fuel lines while it's disassembled. I see trash in the tanks so I need to clean them well. The fuel filter was new and looks clean. Am I doing the right thing to try to fix this? Could the fuel pump be bad? Or is the trash I see blocking flow? The tractor was run last year for a day with the fuel cap off so I am sure this caused some trash to enter the tank. Could this cause the problem? Or do I have an air leak somewhere?

What's the best way to flush and clean the tanks? I have already removed all hoses and the fuel sending unit.

 

[ArtMech]

My kubota M 6800 randomly starts chugging and then shuts off. I go thru the bleeding air process and it fires right up again and runs fine until the next time. I have removed both tanks and plan to replace all fuel lines while it's disassembled. I see trash in the tanks so I need to clean them well. The fuel filter was new and looks clean. Am I doing the right thing to try to fix this? Could the fuel pump be bad? Or is the trash I see blocking flow? The tractor was run last year for a day with the fuel cap off so I am sure this caused some trash to enter the tank. Could this cause the problem? Or do I have an air leak somewhere?

What's the best way to flush and clean the tanks? I have already removed all hoses and the fuel sending unit.

Yes, if you see trash in the tanks, it could block the fuel flow.
I have had exactly the same issue - the pieces of cedar nuts inside the tanks were blocking my tractor's fuel supply system.
My advice is to do the simpliest procedure first - to flush the tanks. With the tank(s) removed fill it(them) by 1.5-2 liters of clean diesel fuel, swill out by shaking it(them) in the hands and emptify. Separate trash from spilled out fuel, infuse back the same fuel into the tank and repeat swilling procedure again and again until clean fuel (without trash) spills out from a tank.
No need to replace fuel lines (or hoses). Just clean them up making sure that compressed air freely blows thru them. Check the water separator whether it is not blocked with trash. The trash could not enter anywhere further than water separator so it will not block or demage fuel pumps - neither low pressure, nor high pressure. Especially because of that that between water separator and the fuel pumps there is a fuel filter.

Hope it helps.
Good luck!

 

[Gary Fowler]

You should have a water separator (fuel bowl). After cleaning the tank as described, remove the glass bowl from the water separator,remove the down stream fuel line and lightly blow compressed air backward thru the water separator to clean any sediment that might be stuck in the upper screen. Reinstall the bowl and blow air into the line again to clean the line to the tank. The tank now being clean, the fuel bowl clean and all lines coming from the tank to the fuel bowl clean, now change the fuel filters to be sure you have nothing blocking them and then refill the tank with clean fuel. Bleed off all the air from the filters, fuel bowl till no more bubbles. You should be good to go at that point. You may also have to bleed off the injector pump if it has a bleed vent.

 

[Egon]

Removal of the tank will facilitate a proper flush and drain of the tank debris.

 

[tonyoz]

Where the fuel line from the tank connects to the lift pump there should be a banjo fitting with a strainer inside that may need cleaning. I've had this problem on heaps of Jap engines over the years and that strainer is never listed in the manuals.

 

[HCJtractor]

Thanks for the responses. I plan to clean the tanks tonight and start tracing and clearing all fuel lines. I have not found any strainer. I would have thought there would have been one in the tank at the fuel intake, but it is just an open tube. It seems the first filter in line is the water separator, then the fuel pump and of course the fuel filter. I have not found any other strainers or filters yet. I see some crud and small sticks in the tank so I hope my problem was caused by these obstructing the intake line. The main filter was clean as could be, and the drained diesel looked clear.

 

[ArtMech]

I have not found any other strainers or filters yet.

The strainer of your case is a water separator at the same time. That strainer has a great feature, it passes fuel, but not allows water to be passed until red float (ring) lies at the bottom of a glass bowl.

And you're right the low pressure fuel pump is fitted between water separator and fuel filter. Only high pressure fuel pump goes after the fuel filter. Sorry for confusion.