Yanmar 1GM10 - Smoke, No Power

[billmcc]

I am at my wit's end to diagnose the cause of my problem. My engine throws out clouds of black smoke and oil under any kind of load and I can only get 2.5Kts (plus 1 Kt if alternator belt disconnected) instead of my customary 5Kts.
Have had injector pump & injector overhauled
New piston rings fitted and bore honed
Exhaust checked
Prop and gearbox not producing extra drag
Fitted cylinder head from known good engine
New Gaskets
Fresh fuel and fuel filters fitted
Compression check shows 40 Bar with no abnormal leakage

All work completed by a well-qualified marine mechanic who is also puzzled

All suggestions welcome.

Bill.

[NCboatrx]

I suspect that this is caused by either the injector which may have the incorrect tip or the fuel adjustment for the injection pump. Does the engine rev up cleanly in neutral?
Stanley

[mesquaukee]

Timing of injection is late. Incomplete combustion and lots of oil is the result with lack of power.

[Chief Engineer]

There are a number of shims for the injector pump. They are fro timing purposes. They may have been left out upon re-assembly

[billmcc]

Thanks guys. Stanley:This is not an injector problem - mine has been fitted with new nozzle, but I have also tried an injector from a friend's boat and borrowed head has its own injector. Mesquaquee:Timing was checked but will re-check tomorrow. Chief:Will check with mechanic about shims, but bear in mind problem existed before we removed pump. Bill.

[NCboatrx]

Does the engine rev up cleanly in neutral?

[Chief Engineer]

Clouds of black smoke and oil?

There should be a breather tube coming off the valve cover and going to the air intake. Take the hose off and start the engine....there should be a small amount of vapour coming out.....if it is a lot....you have leaking valve stem seals.

[Sailmonkey]

I repaired a 2gm once that had a similar problem, the injector fits into a precombustion chamber. The chamber had broken open....removed head, replaced chamber, problem gone.

[Chief Engineer]

I have seen that too. There are two copper rings, one copper ring(looks like a fender washer and a composite gasket...if they go bad or are missing you will get black smoke....the pre-combustion chamber is in two halves....the lower one may be plugged or damaged.

[s/v 'Faith']

What was the original presenting problem that caused you to do all this work in the first place? Was it the 'smoke, no power' problem you are still having?

It really does sound like a timing issue, or a bad injector (which it sounds like you ruled out).

Is the line between the injector and the pump kinked, was it replaced?

Who did the rebuild of the pump?

Was it a rebuild or did they swap it with another one they rebuilt?

Originally Posted by billmcc

I am at my wit's end to diagnose the cause of my problem. My engine throws out clouds of black smoke and oil under any kind of load and I can only get 2.5Kts (plus 1 Kt if alternator belt disconnected) instead of my customary 5Kts.
Have had injector pump & injector overhauled
New piston rings fitted and bore honed
Exhaust checked
Prop and gearbox not producing extra drag
Fitted cylinder head from known good engine
New Gaskets
Fresh fuel and fuel filters fitted
Compression check shows 40 Bar with no abnormal leakage

All work completed by a well-qualified marine mechanic who is also puzzled

All suggestions welcome.

Bill.

[s/v 'Faith']

Originally Posted by Sailmonkey

I repaired a 2gm once that had a similar problem, the injector fits into a precombustion chamber. The chamber had broken open....removed head, replaced chamber, problem gone.

Originally Posted by Chief Engineer

I have seen that too. There are two copper rings, one copper ring(looks like a fender washer and a composite gasket...if they go bad or are missing you will get black smoke....the pre-combustion chamber is in two halves....the lower one may be plugged or damaged.

If the problem is new, yes. But it seems like if they swapped heads they would have eliminated this.

.....Fitted cylinder head from known good engine.....

[delmarrey]

Too much load
Improper propeller
Dirty intake silencer
Improper fuel
Faulty spray of fuel injector

I would guess one of the last two............._/)

[Chief Engineer]

with your observation.

Originally Posted by Chief Engineer

Clouds of black smoke and oil?

There should be a breather tube coming off the valve cover and going to the air intake. Take the hose off and start the engine....there should be a small amount of vapour coming out.....if it is a lot....you have leaking valve stem seals.

[billmcc]

Faith: Original presenting problem was 'smoke, no power' and occurred a week after I fitted a new alternator (can't be a connection - surely?). No lines kinked. Pump rebuild by full-time diesel repair shop who have done work for my company for years. Genuine Yanmar parts fitted at cost of 250 euro!
Chief: I am aware protector on injector can break. I wasn't broke on original head and isn't broke on loan head I am trialling. Fitted 'complete' gasket set (225 euro) but it did not include valve stem oil seals but they look ok on both heads. Breather problems was my first port of call, but I will re-visit all the suggestions posted and my thanks to all contributors.
Anybody: Does anybody know what the spec is for compression on 1GM10? Is 40 bar enough?

[Tellie]

Originally Posted by Chief Engineer

with your observation.

Wouldn't that be precluded by changing out the head with a known good head Chief?

I'm "Assuming" if the known good head is good and the valves are timed right. I'd be looking back at the fuel pump and perhaps the ring replacement that was done. Was the cylinder properly measured and were the rings installed correctly. If compression is within good range I'd go back to the pump since it has been worked on. Even the best of mechanics can make a small mistake every now and then.
40 bar of pressure is about 580psi. I would think that's a bit high if that's an accurate reading. I believe it should be around 430-470? An accurate high compression reading could be signs of trouble as well.