Yanmar 2QM15- Out of Ideas

[terrylad]

This is weird. I've had exactly the same symptoms on my Yanmar 3GM30 and have done all the same 'fixes'. Had the injectors tested and they were OK. Still got the problem at 2000+rpm. Maybe the injector test was not as far-reaching as it could have been. Next test for me is to open up the return line and check for bubbles in the return flow.....But, my return line goes straight back to the tank, not to the secondary filter as described above. Doesn't that mean that its injecting air back into the fuel line - which wouldn't happen in my case (going straight back to the tank)?

[WestcoastCrown]

Sorry to hear you have the same symptoms Terrylad.
Plumbing the return line back to the tank removed the possilbilty of air being pumped back into the secondary filter. So I dont see where that could add to the problem in your case.

The injectors on my boat had been replaced approx 30 engine hours ago, according to the work order provided by the previous owner. However the time lapse was five years and as the boat saw little or no use during that period it probably didnt do anything much good. The cost difference between servicing or replacing them was only a couple of hundred dollars, so I opted for the new ones. Good luck and let us know how you make out.

[terrylad]

Thanks for responding WestcoastCrown. After tightening all the fuel feed system, I ran it again today and still have the same, predictable fault. Run the engine at 2700-3000 for 10 minutes under load - no problem. Then it increases speed very slightly and starts misfiring, chuffing out light blue clouds of smoke. The engine recovers at lower revs but won't go over 2200 for more than a minute before it starts misfiring again. So the problem comes in after the engine has been running for a while. I'm at a loss whether to start reconditioning the injector pump, or replacing each injector until the fault goes away. I'm on a pension, so I can only afford to purchase one new injector each month! Having a mechanic on the boat is out of the question, the rates they charge here.

[Cestmoi]

If a fuel line starts to colaspe then when the demand lessens the line reopens the engine would respond accordingly. I have found if a rubber fuel line is cut or torn inside it would act like a check valve. Maybe when the new fuel line was installed and error occured. I am interested to hear the final fix since I have a old 2GM I am repairing.

[WestcoastCrown]

Yes Terrylad, Cestmoi has a good point. The final test for us was when I ran a jerry can with intenal filter and fresh fuel, through a 12v pump and new hose, directly to the engine mounted secondary filter. The problem reoccured and at that point I could rule out the fuel supply system.
I have been told that if the engine revs up slightly before it bottoms out, then it is a supply/starvation problem. Ours never rev'd up before bottoming out.
I am also interested to hear how you make out.

[sailor3333]

By plumbing a direct fuel supply and return line to your injector pump and using a jug of fresh fuel, you can isolate the problem. All that's needed is some clear tubing (watch for air bubbles), a little electric cube pump and inline filter. If problem persists after that, you're into other issues like governor springs. If it doesn't, the issue lies with your fuel delivery system and the possibilities already mentioned in this thread. You have an engine that will "purr like a kitten" so it's hard to imagine that you have a really serious problem.

[terrylad]

My problem turned out to be the fuel pump (perforated diaphragm), after I had the Injector Pump rebuilt - very expensive and complicated to remove and reinstall, but the engine now seems to run with more power than it had before, so hopefully I've killed several birds at one time.

[WestcoastCrown]

Terrylad, glad to hear your boat is running well. Not good news on the injection pump, but maybe it was part of the problem? It certainly sounds like it won't be a problem again.
Ours has been running well since the new injectors and fuel system plumbing change, but I wonder if I will even stop jumping everytme I hear a miniscule change in engine pitch!
Cheers.

[terrylad]

Originally Posted by WestcoastCrown

Terrylad, glad to hear your boat is running well. Not good news on the injection pump, but maybe it was part of the problem? It certainly sounds like it won't be a problem again.
Ours has been running well since the new injectors and fuel system plumbing change, but I wonder if I will even stop jumping everytme I hear a miniscule change in engine pitch!
Cheers.

I have the same syndrome. Its called Yanmar PTSD.

I spoke to three different Yanmar distributors at the Newport Boat Show last week and only one, a former mechanic, nailed the problem, emphasising the big number of incidences in the past. The others gabbled on about a dozen other causes, but ended up sounding like sales folks rather than experienced mechanics.

Good luck with your PTSD. It will diminish with time, I'm sure....

[David W]

Originally Posted by terrylad

I have the same syndrome. Its called Yanmar PTSD.

I spoke to three different Yanmar distributors at the Newport Boat Show last week and only one, a former mechanic, nailed the problem, emphasising the big number of incidences in the past. The others gabbled on about a dozen other causes, but ended up sounding like sales folks rather than experienced mechanics.

Good luck with your PTSD. It will diminish with time, I'm sure....

Gents, as a 2QM15 owner, I've been following this thread with interest. If it gives anyone any comfort, ours runs perfectly (in fact better than before after using a liberal amount of cetane booster over the summer)

Yesterday, in temps of about 65 degs F or 18 C, she started after about five rotations without using the pre-heater. I was pretty pleased.

[charliehows]

i consider that yanmar PTSD as a safety feature - i always have a plan B ready for if the engine conks - sails ready and a healthy distance off any lee shore if theres wind, danforth with 50m of hawser on deck if none (i dont use the cqr with chain cos with no eng. its too hard to get it up quickly) always know the tide - amazing how far you can get just riding the tide - etc etc. The more organised i get, the more reliable the damn engine gets...