L2350 with constant air in fuel lines?

Rrrracer

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May 12, 2016
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Indiana
Hey everyone, I'm trying to help out my elderly neighbor with his L2350 and so far I am failing! I have a lot of experience with gas engines/automotive but quickly getting a crash course in diesel...

The tractor will start and run great when it's cold. It will run well for about 30 minutes, then suddenly start to lose power, eventually stalling the engine. If it sits and cools back down, we're back to running well.

I've replaced the fuel feed hoses from tank->filter and filter->injector pump. The fuel filter is new. I bled the whole thing from filter to injectors; the bleed at the filter is clean, no air.

However, I get a continuous stream of tiny bubbles (sometimes big) from the bleed at the injector pump. I also get continuous bubbles at each injector on the engine (cracking them open ever so slightly while the engine is running.)

After it does stall, I can restart the engine and it will run for a few seconds and then die again.

I should mention that the tractor only has 570 hours on it, so not a lot of use.

It acts like a brake bleeder that is pulling air in from the threads, but I'm making sure that I only crack it open just enough to start the bleed process, so I don't think it's that.

It seems as if it is pulling a small amount of air in from somewhere else, so I'm polling the crowd to see if anyone has ideas on where to start. Bad injection pump gasket? A deteriorated o-ring somewhere? Thanks!
 
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1970cs

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Apr 26, 2016
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You might want to put on tygon fuel lines on the supply side. It's clear enough to see where the introduction of air is occurring. Make sure that all banjo fittings have a fresh set of washers on the supply side.

Pat
 

RCW

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Racer - Pat and Bulldog bring up good points, and I would start there. They have much more experience than I do. :eek:

Other things to rule out - since it runs 30 minutes no problem, I would also make sure the fuel tank cap vent is clear, and also there is no trash plugging the tank outlet.

After running a while, a plugged vent will create a small vacuum and starve it. Also, sometimes it takes a while for junk in the tank to get drawn to and block the fuel outlet, and cause same issue.

And with all that said - there is a good amount of fuel in the tank? Don't trust any fuel gauges on a Kubota.....

Good luck - and you're a good neighbor!:)
 
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Tooljunkie

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As rcw said, you need to actually see the fuel outlet where fuel leaves the tank. Perhaps there is something blocking screen, if it has one.
And fuel vent. Try draining tank into a jug via gravity, see if it will all drain out or airlocks.
Good time to checkfor water and algae too.
 

North Idaho Wolfman

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Sent you a PM with a link for a service manual, will help with all the parts locations and testing. ;)
 

Daren Todd

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Double check you clamps where you have swapped the fuel lines. If you can rotate the hose by hand, then the clamps aren't tight enough.
 
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Rrrracer

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May 12, 2016
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Indiana
Thanks everyone. I'm a firm believer in the KISS method and I believe the problem is something simple, so I'll start at the tank and work my way up from there.

The cap vents are clear, and the tank is full of fuel. I've replaced the hoses and the bleed at the filter is clear of air.

Although the problem was pre-existing, the filter was replaced by someone else, so I'll make sure I check it and the seal... will report back!
 

Rrrracer

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May 12, 2016
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Indiana
Solved. It was the fuel. I can't explain it, don't know why, but I drained the tank and put fresh diesel in it, and it runs like a champ. Thanks everyone for your input, glad I got to the bottom of it... and next time, that's where I'm gonna start :)