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Old 27-05-2020, 00:22   #1
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Diesel fuel return line

Hi there!
I am working on a backup generator I bought recently that came with no fuel tank. I am going to use a tank off an old Massey Fergusson Tractor about 30L that will do just fine.
My question is this. The return line on the tank has two lines going in, and this got me stumped. Why would I need two return lines?
The engine in the generator is a Kubota D1105. I tried to find a fitting to replace the existing one, see photo, but the diesel parts shop told me, that is the breather line.
I doubt that there will be much breathin going on, if there is a flow of diesel retuning, but I may be wrong.
What do you think?
Should I try to find a fitting with a single line going in there? Or attach a bit of fuel line and hang it upwards with a breather valve at the end, or just block it off??
Your replies are appreciated.

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Old 27-05-2020, 00:28   #2
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Re: Diesel fuel return line

The breather line allows air out when filling the tank. If the air can only get out via the filling line you get a lot of diesel backflow when filling the tank.
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Old 27-05-2020, 00:44   #3
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Re: Diesel fuel return line

There is no filling line. It is an open tank with a lid on top (see photo) like a motorcycle tank. Plenty of air able to go out when filling. I understand the need for a return line from the injectors, but that other line going in the same opening where the return from the injectors goes in seems mysterious to me. The donator tractor was a 6 cyl engine, much bigger engine than my little kubota but still I have never seen dual return fuel line.

Then again this seems to be a common set up. More confused.
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Old 27-05-2020, 01:18   #4
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Re: Diesel fuel return line

It is a vent (or breather). It allows air in when your engine is pulling fuel out of the tank. Quite common to use one hole in the tank for the return line and the vent. Just make sure the outlet of the vent line is a couple of inches above the top of the tank.
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Old 27-05-2020, 01:40   #5
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Re: Diesel fuel return line

Don't forget to use a screened vent for the breather line, wasps and other nasties like to explore holes, and that's probably not good for the fuel
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Old 27-05-2020, 01:48   #6
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Re: Diesel fuel return line

Quote:
Originally Posted by Marc1 View Post
Hi there!
I am working on a backup generator I bought recently that came with no fuel tank. I am going to use a tank off an old Massey Fergusson Tractor about 30L that will do just fine.
My question is this. The return line on the tank has two lines going in, and this got me stumped. Why would I need two return lines?
The engine in the generator is a Kubota D1105. I tried to find a fitting to replace the existing one, see photo, but the diesel parts shop told me, that is the breather line.
I doubt that there will be much breathin going on, if there is a flow of diesel retuning, but I may be wrong.
What do you think?
Should I try to find a fitting with a single line going in there? Or attach a bit of fuel line and hang it upwards with a breather valve at the end, or just block it off??
Your replies are appreciated.

https://scontent.fsyd3-1.fna.fbcdn.n...20&oe=5EF595CA
https://scontent.fsyd3-1.fna.fbcdn.n...3b&oe=5EF356D7
Probably a tank vent

The tank must have a vent or else you will pull a vacuum when fuel is burned and the lost volume is not replaced by air
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Old 27-05-2020, 10:45   #7
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Re: Diesel fuel return line

No breather equals no flow. Must have.
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Old 27-05-2020, 11:11   #8
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Re: Diesel fuel return line

Most industrial equipment lives in a dirty environment and will have a vent line separate from the fill cover so the normal fuel feed vent can be filtered in normally run. The fill cap on our old International Utility has a large filtered fill cap in addition to the vent line.
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Old 27-05-2020, 13:13   #9
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Re: Diesel fuel return line

wouldn't a Vee style engine have two return lines? one for each cylinder bank?
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Old 27-05-2020, 13:49   #10
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Re: Diesel fuel return line

Quote:
Originally Posted by Marc1 View Post
Hi there!
I am working on a backup generator I bought recently that came with no fuel tank. I am going to use a tank off an old Massey Fergusson Tractor about 30L that will do just fine.
My question is this. The return line on the tank has two lines going in, and this got me stumped. Why would I need two return lines?
The engine in the generator is a Kubota D1105. I tried to find a fitting to replace the existing one, see photo, but the diesel parts shop told me, that is the breather line.
I doubt that there will be much breathin going on, if there is a flow of diesel retuning, but I may be wrong.
What do you think?
Should I try to find a fitting with a single line going in there? Or attach a bit of fuel line and hang it upwards with a breather valve at the end, or just block it off??
Your replies are appreciated.

https://scontent.fsyd3-1.fna.fbcdn.n...20&oe=5EF595CA
https://scontent.fsyd3-1.fna.fbcdn.n...3b&oe=5EF356D7


Was the Massey tractor diesel?

I donít see how it could have been.

The kubota will need to move about 5 gph into the fuel return, no way you can share it with the vent.

Iíd add a vent to the tank top and plum the fuel return to one side of the t and blank the other.
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Old 27-05-2020, 14:25   #11
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Re: Diesel fuel return line

You need an outlet line to the injector pump, a return line from the pump to the tank or tank side of the fuel filter if it has two inlets, and one breather pipe terminating in an insect proof filter preferably outside the hull above deck level and well above the level of that tank. Sometimes the fuel cap has a one-way valve in it, and the third line is not present. This idea can lead to a pressure build-up in the tank, although not a very high pressure, it can still be annoying.

When I have had the third line present, or I have added a third line to the fuel cap or closely to it, I have extended it to vent outside the vessel and into an insect proof screened filter. A good idea is to use a motor vehicle or truck self-purging carbon filter, then you are less likely to get that diesel smell. If you use this option you will need one more suction line from the filter to the engine air inlet manifold.
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Old 27-05-2020, 15:45   #12
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Re: Diesel fuel return line

Quote:
Originally Posted by coastalexplorer View Post
wouldn't a Vee style engine have two return lines? one for each cylinder bank?

That would be my guess with a 6 cylinder engine.
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