Yanmar 3ym30 Problem

[RobD527]

Hello

I have a Yanmar 3ym30 that runs great up to 2000 RPM
When you go to 3000 RPM it will be ok for a minute then it will drop RPM and start shaking to almost stalling and then will start running fine again up to 2000 RPM

Carrier bearing is good
Thought it might fuel related changed fuel filter and oil without any change

Any ideas ?

Thanks

[sailorchic34]

Check for a partly clogged pickup line in the tank or a clogged return line. Could be a vacuum leak in the fuel system, which is always fun to find.

Use a 5 gallon fuel can and run temp lines to fuel pump and return. If the engine runs fine, it's either clogged /collapsed fuel line or clogged fuel pickup in the tank.

Vacuum leaks are a royal pain to find.

[HiAndDri]

Originally Posted by sailorchic34

Check for a partly clogged pickup line in the tank or a clogged return line. Could be a vacuum leak in the fuel system, which is always fun to find.

Use a 5 gallon fuel can and run temp lines to fuel pump and return. If the engine runs fine, it's either clogged /collapsed fuel line or clogged fuel pickup in the tank.

Vacuum leaks are a royal pain to find.

Got the same engine with same symptoms and this was the cause.

[RonRicco]

Did you change the Racor and the secondary filter. I have had the exact symptoms and it was the secondary filter element.

[HiAndDri]

Originally Posted by sailorchic34

Check for a partly clogged pickup line in the tank or a clogged return line. Could be a vacuum leak in the fuel system, which is always fun to find.

Use a 5 gallon fuel can and run temp lines to fuel pump and return. If the engine runs fine, it's either clogged /collapsed fuel line or clogged fuel pickup in the tank.

Vacuum leaks are a royal pain to find.

Same engine and same symptoms. This was my my problem, the gunk in the plastic tray (some sort of paper gasket?) was wrapped around the pickup filter.

[RobD527]

Yes replaced both filters

[Cavalier]

Originally Posted by sailorchic34

Check for a partly clogged pickup line in the tank or a clogged return line. Could be a vacuum leak in the fuel system, which is always fun to find.



Use a 5 gallon fuel can and run temp lines to fuel pump and return. If the engine runs fine, it's either clogged /collapsed fuel line or clogged fuel pickup in the tank.



Vacuum leaks are a royal pain to find.

^^this



Another thing to do is withdraw/remove your pickup from the top of the tank along with its line to the primary racor unit, get a bucket and back-blow the diesel out into the bucket and see what comes out.. Large clogs can act as variable check-valves depending on flow-rate!

[RobD527]

I will be checking this first and will update the outcome