Yanmar 3 GM 30 F works for a minute and then dies

[Gennady22]

Hi all!

We have this problem: when we start our Yanmar 3 GM 30 F engine, it runs for a minute, and then dies down. Moreover, there is a thick black soot coming out of the exhaust, while before it was clean water. When a mechanic came over today, he said that air must be getting somewhere, but he was not able to understand where. He did change the 2 fuel filters - the large one and the small one, on the engine.

Hope someone can help me understand this problem.

Thank you.

[Wotname]

Do the simple stuff first!

1. Remove and check the exhaust mixing elbow. It is very likely to be restricted due to low load operation.

2. Remove fuel tank cap to ensure there is no vacuum forming in the tank due to blocked breather.

If these are OK, we can move on to other possible issues.

[Gennady22]

Please, explain to a new guy how to remove the exhaust mixing elbow on the engine. Also, which fule tank cap do you mean: the one where I pour the diesel? Thanks for answer.