J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Engine Trouble

Hey all,

Motoring in this afternoon at about 1900 rpms and my Yanmar 2QM suddenly slows and dies. Bummer. Tried to restart it, no luck. Motor wasn't overheating and raw water cooling was working fine. I actuated the manual lift and confirmed that there was diesel flowing. Here are a couple clues, I generally get it to fire by poping it into neutral mode and giving it some throttle as I'm cranking. Now, when I'm trying to start it in neutral by giving it some throttle, it just cranks normally and won't catch. I'm thinking blockage at the injector? Any Ideas would be most appreciated, supposed to leave on a little cruise tomorrow!

Thanks,

Josh

just a slow steady die? both injectors go at same time?
perhaps not injectors.

your starting procedure is standard.

It happened fairly quickly, engine running smooth at 1900, making about 5.5 kts. Then I think I heard a subtle change in the engine tone, it seemed slightly more tinny. 30 seconds later, engine revs dropped, engine died and thats where I am now.

Now I'm thinking that maybe my exhaust elbow is blocked up and by running the engine a little higher than normal maybe it backed up and killed the engine? If this happened, that do I need to do to get the engine running again (once I replace the part?)

I'd suggest checking for sources of air entering the fuel system - loose fittings and such, then bleeding through to the injectors while watching for bubbles. Also checking that the tank vent plumbing is clear would be a good idea.

GL,

-Chris

Update. I think you were right on Chris. I was following the fuel, clear up to the low pressure pump but very aerated and white from the outlet of the high pressure pump. (see picture) The hose that connects low pressure and high pressure pump shows signs of cracking and wear, unfortunately I have to wait for the Yanmar parts department to open tomorrow before I can get a new one and keep testing. Could this be the culprit or am I chasing a red herring?

You could have diesel bug too - algae that grows in the fuel and plugs the filters. Solution is to pump the tank dry, change the filters and bleed the system.

would the diesel bug clog the injectors? I'm still getting fuel past the racor and fuel filter into the low pressure pump and into the high pressure pump (where it seems to be being aerated), if filter were clogged would I still be moving diesel?

It is possible at a reduced rate - hence the engine is starved for fuel. Pour the fuel into a glass and see if it looks milky. Any sign of particulates or fine bubbles is an indication of contamination. Condensed water from moisture can do the same thing to plug the filters.

ok, well once i repair the low pressure to high pressure line, drain and replace filters, will I need to pull the injectors to get them "unstuck"? or should the engine start at that point and burn out and injector blockage? Thanks for your help guys.

Update: some questions answered and some new. Well it's not air that's mixing with the diesel, it's water. Diesel cap was cross threaded and when it dumped rain for a few days, water must have gotten into the tank. Draining lines, replacing racor, fuel filter et all. Found something very strange when I opened tank to drain and clean out, the diesel/water in there is almost black! Obviously oil must have entered via fuel return line, what might account for this? Draining, wiping clean and dry and starting with fresh diesel. Will change oil too just to be thorough.