Yanmar cutting out

[islandskip]

Need some help with one of my Yanmar engines. I have two Yanmar 4LHA-STZE engines. Both have separate fuels tanks and also share an auxillary tank. On a recent trip, the starboard Yanmar starting loosing RPM at cruising RPM (2800). It would either drop down to 1000 RPM and then rev back up or completely shutdown. Working the throttle when trying to restart would restart the engine. If I kept the RPM at 1500 it would run longer but I could hear it having a problem. This symptom occurred on both the auxillary fuel tank and main fuel tank. The port engine ran fine on the auxillary tank during this same time period. I have changed the fuel line coming from the racor filter and changed the racor fuel/water separator. I'm not sure at this point if the problem is with the injectors or the fuel injector pump. Any help will be appreciated.

v/r,
islandskip

 

[Grub54891]

Re: Yanmar cutting out

Does it have a mechanical lift pump before the injection pump? That could be going bad on that motor. Any air leaks on the suction side of the systym would cause issues also. Or it's possible the pick up tube on the tank is plugged up.
Hope this helps!
Grub

 

[islandskip]

Re: Yanmar cutting out

Does it have a mechanical lift pump before the injection pump? That could be going bad on that motor. Any air leaks on the suction side of the systym would cause issues also. Or it's possible the pick up tube on the tank is plugged up.
Hope this helps!
Grub

Hi Grub,
Yes it does according to the manual. My boat is on a mooring and it's been a little rought lately to get out to the boat and verify. Is there a rebuild kit for this pump?

 

[Grub54891]

Re: Yanmar cutting out

I don't know if there is a rebuild kit for the lift pump. If it were mine I'd just get a new one to get it going.I'm not saying the problem is the lift pump but it's something to check. I guess you could test it by switching lines from one motor to another or swapping pumps and see if the problem switches sides. Let us know what you find!
Grub