Strange Behavior After Draining Fuel Tank Because Of Water [VIDEO]

[dodge man]

If you disconnect a fuel line does the fuel flow freely? I've read a lot of stories about people that will have a piece of trash float into and out of the outlet to the fuel tank.

 

[Lobanz]

[SOLVED] Strange Behavior After Draining Fuel Tank Because Of Water [VIDEO]

SOLVED!!! :cool2: :jump: :dance1: :hyper: :applause: :drink:

I strongly suspected the lift pump so I wired in a cheap electric fuel pump in place of the mechanical lift pump. Just unplugged the mechanical pump and electric pump fit right in there. Was very simple. And It ran like it had a new lease on life! Happy and perky as she's ever been! Mowed for several hours. Engine was running for about 5 hours straight with no problems. No freaky power loss. VERY happy now. I don't know about you, but I get depressed when my tractor is sick.

So, I've ordered a new lift pump and new fuel line and a fuel shutoff valve. I'm also going to swap out the existing fuel filter for a Racor 120AS water separating filter -- will have to fabricate a new mounting bracket.

Does anyone know what the line that returns to the tank on the existing kubota filter is there for? Can't pressure relief because the fuel filter is on the suction side of the lift pump. Is it like a vacuum breaker so that fuel will fill the fuel bowl for you when you change the fuel filter? I runs back to the top of the tank. Must have a check valve built into fuel filter housing. If that's all it's for, maybe I can just cap it off and not use it? Or maybe install a check valve in the line and run it to the second input on the Racor?


Thanks!

 

[3Lfarms]

Sounds like a return for an air separator.

 

[Dave M7040]

Re: [SOLVED] Strange Behavior After Draining Fuel Tank Because Of Water [VIDEO]

SOLVED!!! :cool2: :jump: :dance1: :hyper: :applause: :drink:

I strongly suspected the lift pump so I wired in a cheap electric fuel pump in place of the mechanical lift pump. Just unplugged the mechanical pump and electric pump fit right in there. Was very simple. And It ran like it had a new lease on life! Happy and perky as she's ever been! Mowed for several hours. Engine was running for about 5 hours straight with no problems. No freaky power loss. VERY happy now. I don't know about you, but I get depressed when my tractor is sick.

So, I've ordered a new lift pump and new fuel line and a fuel shutoff valve. I'm also going to swap out the existing fuel filter for a Racor 120AS water separating filter -- will have to fabricate a new mounting bracket.

Does anyone know what the line that returns to the tank on the existing kubota filter is there for? Can't pressure relief because the fuel filter is on the suction side of the lift pump. Is it like a vacuum breaker so that fuel will fill the fuel bowl for you when you change the fuel filter? I runs back to the top of the tank. Must have a check valve built into fuel filter housing. If that's all it's for, maybe I can just cap it off and not use it? Or maybe install a check valve in the line and run it to the second input on the Racor?


Thanks!

I dont know about your specific tractor but most diesels' injectors have small amount of internal leakage which is routed back to the tank through low pressure lines and fittings.

The filter system also has provisions to allow air to get back to the tank before it gets to the injection pump.
Often this flow path has a restrictor in the circuit somewhere so the amount of return fuel/air is small and not starving the engine for fuel. Often the injector drain line and the filter bleed line are joined together.

Sometimes these return lines to the tank, although entering the tank at the top, extend to the bottom of the tank to avoid any air being sucked back as could happen if this return line just discharged into the very top of the tank. Strange flows happen as engines cool down and tractors sit in the sun or very cold temps.

I would be extremely cautious about "re-engineering," what Kubota has designed in the way of the routing of hoses.

Dave M7040

 

[V65ozzie]

Not sure, but check to see if somewhere in the fuel line is a small plastic or metal filter, I find these all the time, and they get stopped up with trash.

 

[Redlands Okie]

Congrats on the puzzle solving

 

[Lobanz]

Re: [SOLVED] Strange Behavior After Draining Fuel Tank Because Of Water [VIDEO]

I dont know about your specific tractor but most diesels' injectors have small amount of internal leakage which is routed back to the tank through low pressure lines and fittings.

The filter system also has provisions to allow air to get back to the tank before it gets to the injection pump.
Often this flow path has a restrictor in the circuit somewhere so the amount of return fuel/air is small and not starving the engine for fuel. Often the injector drain line and the filter bleed line are joined together.

Sometimes these return lines to the tank, although entering the tank at the top, extend to the bottom of the tank to avoid any air being sucked back as could happen if this return line just discharged into the very top of the tank. Strange flows happen as engines cool down and tractors sit in the sun or very cold temps.

I would be extremely cautious about "re-engineering," what Kubota has designed in the way of the routing of hoses.

Dave M7040

Here is the diagram. Definitely not related to injector return. The injector return runs into a separate input to the top of the tank. Filter return simply returns straight back to its own connection to the top of tank and no restrictor is shown (it could be built into fuel filter housing though).




--- Lobanz

 

[Dave M7040]

Re: [SOLVED] Strange Behavior After Draining Fuel Tank Because Of Water [VIDEO]

Here is the diagram. Definitely not related to injector return. The injector return runs into a separate input to the top of the tank. Filter return simply returns straight back to its own connection to the top of tank and no restrictor is shown (it could be built into fuel filter housing though).

View attachment 522956


--- Lobanz

Thanks for the parts illustration. It appears there are two lines returning to the top of the fuel tank and they are not combined as I thought they might be

One line from the injectors and another, right beside it, from the fuel filter.

This question just has to do with my own curiosity.
Can you see into the tank in the area where the two return lines are?
If you can, I would like to know if the two lines just end inside the upper part of the tank or if the one from the filter goes down into the tank near the bottom so its end i always in fuel.

I recall a comment you made earlier about the mechanical fuel pump suction port being on the outlet port of the filter and this is visible in the parts illustration.

Dave M7040

 

[Lobanz]

Re: [SOLVED] Strange Behavior After Draining Fuel Tank Because Of Water [VIDEO]

Thanks for the parts illustration. It appears there are two lines returning to the top of the fuel tank and they are not combined as I thought they might be

One line from the injectors and another, right beside it, from the fuel filter.

This question just has to do with my own curiosity.
Can you see into the tank in the area where the two return lines are?
If you can, I would like to know if the two lines just end inside the upper part of the tank or if the one from the filter goes down into the tank near the bottom so its end i always in fuel.

I recall a comment you made earlier about the mechanical fuel pump suction port being on the outlet port of the filter and this is visible in the parts illustration.

Dave M7040

Thanks Dave!

I just went and looked in the tank. There aren't any tubes in the tank that go down to the bottom. Just a little bump with a hole in it. Walls were smooth and didn't look to be any molded in channels. I would assume that if there were any tubes inside (or even channels) that they should show up on the fuel tank parts diagram below.



I'm thinking that the return from the fuel filter to the top of the tank is to allow air to escape the fuel filter to so that it can fill up with fuel when you change the filter element. Since it's on the suction side of the lift pump, I would have to guess that there is a check valve built into the fuel filter housing to prevent it from sucking air. I don't see any inline check valve and there are no inline devices shown on the fuel system parts diagram.

What are you thinking?

BTW, I have a generator with a Kubota D1105 engine (very similar). It just has a spin on fuel filter cartridge (not a fuel bowl type) and there is no return to tank from the filter, but there is a return to tank from the injectors. It has an external electric lift pump though. It's built on a trailer with a big 60 gal tank.

I'm also toying with mounting the Racor filter on the loader frame instead of making a custom bracket and replacing the existing filter. If I do that, then I can just leave the whole existing fuel filter in place. See where I'm pointing to a mounting point below. This would probably be more protected than where the existing fuel filter is, but it also may be hard to replace the Racor filter element. The loader hydraulic hoses are sort of in the way, but maybe I can make it work. Once filter gets here I'll hold it up there and see what it looks like.




I'm going all super paranoid about water now. I've forsaken using 55 gal drums and pumps. Found a good deal on a 120 gal tank and I can put it where it should gravity feed. Will put one of those Goldenrod water/particulate filters on it and tilt the tank a bit so that any water should run into the tank filter bowl. And both the tractor and the generator are getting a Racor 120AS filter/separator. My old '93 F250 7.3 IDI might get a Racor 500FG2 at some point -- the Racor 500FG2 fuel filter element is only $8 whereas the stock filter is close to $50! And for the tractor, the Racor 2 micron element is about $16 which is about the same price as the Kubota paper fuel filter element. Given the cost of the stock fuel filters, I figure the Racors filter elements won't cost any more and will do a MUCH better job of filtering the fuel.

 

[Lobanz]

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