Yanmar 3YM20 issue: Engine runs for 5 minutes then solenoid shut-off goes off

[louisgo]

Hey there,

I am having troubles with my almost brand new Yanmar Diesel engine, model 3YM20:

Troubles started when the engine died on me because of contaminated fuel that clogged the racor filter, and probably the fuel intake line. I cleaned the tank, put in new fuel with biocide, and changed both the Racor and the micron filters. I also blew into the fuel intake line, towards the tank, to clear the line of anything that would clog it.

Then I had to bleed the air out of the fuel system, all the way to the injectors, multiple times. In this process, one of the fuel return lines ended up breaking and leaking, right at the junction with the injector. this small pipe is very weak and seemed to be corroded, as it was subject to almost no torque. I fixed this leak with JB weld, but it still leaks a little bit.

At this point, the engine will start and run for a few minutes and then die because the shut-off solenoid goes off. I thought my issue was that there was still air in the fuel system, and when I bleed the air using the priming lever and opening the screw on top of the micron filter, air keeps coming out even after almost an hour of pumping. So I am now wondering if I have an air leak...

I also added fuel to the tank before the whole operation. The Racor filter is new, clean and free of water. Engine is almost brand new, with only 40 hours on it.

My questions are the following:
- What could cause the shut-off solenoid to stop the engine? Could air in the fuel system cause this to happen?
- Is it possible that I have to bleed the air for almost and hour (thousands of pump revs) and air still comes out of the bleeding screw?
- Can a leak in the fuel return line cause an air leak in the fuel system that would cause the engine to die?
- How to replace the fuel return line? My mechanics skills being limited, should I get this done by a professional?

Thanks in advance for your help!!

[masonc]

Could be oil or overtemp

[masonc]

Originally Posted by louisgo

?
- How to replace the fuel return line? My mechanics skills being limited, should I get this done by a professional?

Thanks in advance for your help!!

The fuel line can be brazed if you can remove it. Where are you?

Three

[louisgo]

Originally Posted by masonc

Could be oil or overtemp

Are these the only reasons that would trigger the stop solenoid to shut the engine off?

I am located in British Columbia, on Galiano Island!

Thanks for your answers.

[sailormed]

Ther may still be dirt in the fuel line. I had the problem after a severe contamination.
In the "head" of the Racor filter there are two 90° bends, one directing the incoming fuel down and the other one directing the upflowing fuel to horizontal.
Replacing the filters was not enough in my case. Disassemble the racor filterhead and check.
Check both, but the crud will be on the feed side of-course

[Ziggy]

If you have air still coming out of the bleed screw after an hour of pumping, I think it's a safe bet that you have an air leak somewhere. Try methodically bleeding the fuel supply system starting at the Racor and working toward the injectors. A defective or worn gasket or a piece of crud lodged somewhere could cause an air leak.

I don't know why the solenoid would be cutting off--what makes you think this is happening?

If the engine is almost brand new, shouldn't it still be under warranty? Even if you don't have a Yanmar mechanic in your area, the dealer who sold and installed your engine should be willing to at least provide telephone support.

[louisgo]

I don't know why the solenoid would be cutting off--what makes you think this is happening?

If the engine is almost brand new, shouldn't it still be under warranty? Even if you don't have a Yanmar mechanic in your area, the dealer who sold and installed your engine should be willing to at least provide telephone support.

Because when the engine dies, the stop solenoid is clicking, so I think this is what is killing the engine.. But I am confused because from what I understand, a fuel issue or an air leak wouldn't cause the solenoid to stop the engine.

The engine is under warranty but the dealer that installed the engine told me that as I worked on the engine, I might not be able to get warranty to work.. I will still try to make it work though. They are helping me on the phone, but they are busy and I haven't been able to get in touch with them for the past 4 days, which is why I am looking for help on this forum . And I am happy to get all these helpful advices!

Ther may still be dirt in the fuel line. I had the problem after a severe contamination.
In the "head" of the Racor filter there are two 90° bends, one directing the incoming fuel down and the other one directing the upflowing fuel to horizontal.
Replacing the filters was not enough in my case. Disassemble the racor filterhead and check.
Check both, but the crud will be on the feed side of-course

Will check inside of the Racor, thanks for the advice!

[masonc]

When I get difficult to solve issues with a diesel engine, I like to bypass all the problem areas to prove the rest of the system is OK. I would take a 5 gallon jug of diesel, syphon down to a new filter, can be a cheap paper filter, then into the injector pump. The jug has to be above the engine, not hard to do in a sailboat.
The return will go back to the fuel tank so there has to be room in that tank for 5 gallons.
Start the engine. If it keeps running, everything is good and you have an air leak. If you can feed in after the racors, that proves everything else. Feed to the racors, if you are still good, you have a fuel pickup air leak.
You have to prove all the components one by one, unless you suspect one item and can bypass it or replace it.

[Ziggy]

Originally Posted by louisgo

Because when the engine dies, the stop solenoid is clicking, so I think this is what is killing the engine.. But I am confused because from what I understand, a fuel issue or an air leak wouldn't cause the solenoid to stop the engine.

You can eliminate the stop solenoid by unplugging it from the wiring harness. If it doesn't stop by itself, you'll still be able to stop the engine by depressing the manual override button (covered by a rubber boot) on the solenoid.