yanmar 2qm15 fuel problem

[pfirth]

I have the same problem that I posted a month ago (out of town for 3 weeks) in an intermittent dumping of unburnt fuel into the exhaust. Sometimes the engine seems normal, sometimes won't start or little throttle control if it does. The shutoff cable needs to be replaced and is not connected. Will this cause those symptoms? I have a new cable on order, but it's on backorder. Is there any way to test if this is the problem and possibly jury rig a fix until the new cable arrives? Thanks

[Omatako]

The shut-off cable won't give the symptoms you describe unless it is fitted and stuck partially engaged but you have already mentioned that yours is off the engine.

How do you know it's dumping fuel into the exhaust? Is it smoking black profusely? The erratic behaviour could have its roots just about anywhere in the system for pipe connections to injectors to filters to the pump itself.

But I'll wager it's not the stop cable.

[pfirth]

Thanks for your response. The unburned fuel discharges with the exhaust into the water which is quite visible. There is sometimes gray smoke, sometimes white, and sometimes none. I pulled the injectors and had them checked at the shop...they were fine. It seems to be getting a good pulse of fuel to both cylinders from the injector pump, and the engine runs well without smoke after warming up, although changing throttle position will cause it to lose power and discharge raw fuel. I previously had water (fresh) problems in the fuel tank, but have resolved that and checked the tank to see that is no longer an issue. The engine starts immediately and runs well for a short time using starter fluid which indicates to me a fuel mixture problem of some kind. Am I on the right track?

[CalebD]

But I'd be very careful using starting fluid (ether) on your diesel. I seem to recall reading in Nigel Caulder's 'Boatowners Mechanical & Electrical Manual' that he recommends using WD 40 as a starting primer for diesel engines.
I think that the ether is just too volatile for compression engines.

[pfirth]

Thanks Caleb D. It actually was WD 40 and I agree but probably would only use any starting fluid as an indicator or a last resort.

[CrazyRu]

Do not use starting fluid. Period. Unless you like replacing head gaskets.
Don't ask me how I know. Use WD-40, if you really need some boost.

You describe same problems I had with my 2QM15 when I just bough the boat.
In my case it was a problem with a fuel and fuel delivery system.

There is very simple test you can run. Warm up the engine.
Get a small funnel and a hose and attach it directly to the injector pump, by -passing all fuel system - tanks, pump, filters.
Just pour a quart of clean(!) fuel into funnel and let it run by gravity feeding. If engine works well (after initial coughing and splitting) then your problem is with dirty fuel, leaking connections or faulty lift pump. I would give 90% chance that it is a case.

BTW, I don't have shut off cable. Engine shuts by pulling gas cable all the way down.

[FarCry]

Originally Posted by CrazyRu

BTW, I don't have shut off cable. Engine shuts by pulling gas cable all the way down.

Mine doesn't have a shut-off cable either. Seems like something that was added for some reason. Can you not pull the throttle back to kill the engine?

[CrazyRu]

Originally Posted by FarCry

Mine doesn't have a shut-off cable either. Seems like something that was added for some reason. Can you not pull the throttle back to kill the engine?

On 2qm15 kill cable goes to decompression lever. The engine can be shut down either by throttle cable, or by pulling decompression lever. It is usable feature, in case of run-a-way engine it can be shut down from a cockpit. I think.

[Faster]

pfirth.. is there a change in rpm when you see raw fuel, and/or a sudden ticking sound that goes away when the engine runs 'OK'?

If so you may have a intermittently misbehaving injector. In any case removing them and having them serviced might be a good place to start. It's something that you ought to have done periodically and it will put that issue to rest if the cause is something else.

It would be unusual for the engine to suddenly smoke and dump fuel without 'sounding' different and running much rougher...

[pfirth]

I did take the injectors out and had them checked. They were fine. The engine starts slowly catching only if the throttle is in a narrow position range. (3/4) Then it accelerates slowly while dumping some raw fuel thru the exhaust. It runs better as it warms up, stops smoking and dumping fuel but sounds and feels like it's back pressured (won't get full rpm and responds slow to throttle change). When I put it in gear it bogs down completely with raw fuel and black smoke out of the exhaust. The shutoff cable holds the throttle at minimum idle until the spring loaded lever is pulled which lowers the rpm below running speed. Two mechanics said to get that back in place and play with it before calling them out. The symptoms don't sound like that's the problem, but will install it as soon as it arrives. I'm leaning toward the injector pump altho seems to have a steady spurt to both cylinders. Any other ideas?