Yanmar 38 h.p. keeps dieing.

[Bryan]

My '96 Hunter 376 has a 38 H.P. Yanmar Diesel. My problem is that the engine keeps dieing on a random basis. It dies in calm seas, in rough seas, with the tank almost full to almost empty. It will run if I bleed the fuel line. So I conclude that somehow air is getting into the filtering system.My concern is that it will quit when I am single handling the boat or at an inopportune time where it becomes a hazard to me or to other shipping. Any and all suggestions will be appreciated.

 

[Don Alexander]

Fuel Starvation

My 376 engine used to die due to the mesh strainer on the bottom of the dip tube in the tank becoming blocked. It would re start almost immediately and you may have the same problem. I removed this mesh but then the muck in the tank blocked the inlet fitting to the water separator/filter.No way of cleaing the tank properly as there is no drain cock.Best of luck.

 

[Gordon Torresen]

Air in fuel lines

Your conclusion seems accurate. If bleeding is required to restart the engine, it is definately air incursion.Blockage at the pickup tube will exacerbate the problem. The problem is somewhere between the pickup tube and the inlet to the lift pump. What we do to confirm a repair for air incursion is "T" in a vacuum gauge before the lift pump. We then shut off the fuel tank valve and operate the lift pump. You should readily draw close to 15 inches of vacuum - and it should stay after the pumping has stopped. If it does stay, the air is probably coming in at the top of the pickup tube, inside the tank.If the vacuum drops, check each fitting in the circuit, one at a time, until the problem is cured. Also check the gaskets on the primary filter. Another trick is to install a piece of clear plastic tube in the line right at the lift pump. It is sometimes difficult to displace all the air in the tube but you can see a change in the bubble size and and sometimes see the air coming in at the tank end of the clear tube. There should be no air entering the fuel lines. Moreso for the reasons that you describe.

 

[Tom Schlagel]

Are you using additives?

Bryan,To prevent clogs in our fuel system we have always used diesel fuel stabilizer when we top off the tank for the winter and in the summer we use a biocide to prevent algae buildup. Knock on wood...this has worked well for us. Based on what I have read and heard from friends this is a necessary part of ongoing maintenance.