Smoking Yanmar 2GM20F

[olly_love]

We have a Yanmar 2GM20F ( fresh water cooled)

its been running fine for years now however started to smoke a lot recently.

We have had the injectors serviced so not that.

Not using Oil
Not using water
Exhaust Elbow all good
pumping lots of water,
good compression

it mainly smokes on revving or putting revs on.

My next suspect is the fuel pump ( high pressure)

But just wondering peoples thoughts.

 

[Halo]

Looks like part burnt fuel. Is the air filter really clean and no blockage?
Could be a result of heavy loading. Does the prop turn ok when you put it in neutral under sail. If not there could be something round the prop
Have you re propped?

 

[DownWest]

Give the smoke a sniff, as Halo says, looks like poor combustion and I would be surprised if it was the injection pump. Injectors checked? But might need new nozzles.

 

[bignick]

Does it smoke when revved while out of gear as well?

 

[garymalmgren]

Woody charcoal smell = fuel
Oily chemical smell = oil.

Re: My next suspect is the fuel pump ( high pressure)
Why would you suspect the fuel pump? (probably the most expensive thing bolted onto the engine)

RE: We have had the injectors serviced so not that.
What did the injector shop say about the black smoke?

First off I would try a diesel fuel additive.
Run the engine hard to use the fuel in the lines and get some additive into the system.

10 Best Diesel Fuel Additives 2024 | There's One Clear Winner | BestReviews.Guide

gary

 

[olly_love]

Happens when in neutral or gear

Had the injectors done and they needed work, the engine runs sweetly and very smooth

Reason I feel it’s the fuel pump is that they can fail on the racks which dumps fuel into the engine more than needed.

 

[DownWest]

Umm. On the assumption the injectors are spraying correctly, if the pump supplys more fuel, then the engine will go faster, but the govener will control that, so I am not sure I follow you.

 

[dgadee]

Valve guide seals? I have been told they can go stiff and let oil down into the chamber. That was from someone who worked on very large equipment.

 

[Beneteau381]

We have a Yanmar 2GM20F ( fresh water cooled)

its been running fine for years now however started to smoke a lot recently.

We have had the injectors serviced so not that.

Not using Oil
Not using water
Exhaust Elbow all good
pumping lots of water,
good compression

it mainly smokes on revving or putting revs on.

My next suspect is the fuel pump ( high pressure)

But just wondering peoples thoughts.


View attachment 179135View attachment 179136

It looks as if it’s over fuelling or not getting enough air. That is unburned fuel in the last pic. A classic sign of a blocked exhaust? I know you said it’s been done BUT?

 

[Beneteau381]

Happens when in neutral or gear

Had the injectors done and they needed work, the engine runs sweetly and very smooth

Reason I feel it’s the fuel pump is that they can fail on the racks which dumps fuel into the engine more than needed.

The rack is what twists the injector pump elements to increase or decrease their injection amount capacity. It’s a toothed bar usually which is actuated by the governor.
More fuel does indeed mean more speed until the governor, which is controlled by the throttle, adjusts the rack position to suit the throttle position and revs. If the engine reaches the throttle indicated speed than all is well, the governor pulls the rack back to suit speed. However, if the engine is overloaded and doesn’t have enough power to reach speed then the rack pushes the elements wide open or max injection amount and keeps it there and the result is black smoke.
The engine quite plainly isn’t overloaded yet is showing excess fuel not combusting.
The other thing that can cause this is not enough air getting in to give a clean combustion mix. Think old fashioned putting your hand over a petrol engine carburettor to give a richer mix. Diesels are the same. So either a blockage on the inlet, unlikely, a blockage on the exhaust side so not enough air can get in, possible, or a damaged injection pump, rare if it still runs ok otherwise.

 

[westernman]

Could it be diesel bug?

 

[LittleSister]

its been running fine for years now however started to smoke a lot recently.

We have had the injectors serviced so not that.

I wouldn't absolutely rule out a problem with injectors just because you'd paid someone to service them - sometimes mistakes are made or people do a bad job.

Did you have the injectors serviced before or after it started smoking a lot?
Did the heavy smoking come on quickly or slowly?
Have you spoken to the outfit that did the injector servicing about the smoke?

 

[olly_love]

Thanks All,

so we have had the elbow appart and the exhaust hoses and all check. no blockage just sooty.

Weird thing is that we are not using any oil (well no more than a normal 2cylder ) otherwise i would have said piston rings.

No water/ coolant loss. I drained this yesterday and no oil or water in the coolant.

FYI if you ever have to take the HP injector pump out of a 2GM20F its an A**e. everything has to come off the top/side of the engine!

ill have the pump rebuilt and reshim it all and see how we get on.

Diesel Bug
I did wonder about diesel Bug but the smoke isnt all the time just under revs.

FYI We dont smoke when at full RPM only when reving the engine.

and no smoke when normally going along.

 

[bignick]

Starting to think of the weird and the wonderful now, because I would have thought the same as you.

Is it getting to correct temp? If it’s running cold you may get more smoke than normal. Running under load can increase temps a bit, but if a thermostat is stuck open then you may have some strange effects.

I think I’d be inclined to empty the tank, replace the filters and fill back up with white diesel from the forecourt. That at least would rule out a batch of dodgy fuel.

I’d also borrow an IR / Laser thermometer and measure temps on the head. (Suspect you may have one.) You may be able to tell if one of the cylinders is running cooler than the other. This may not be anything to do with cooling, but could be an indicator of poor combustion on one cyl.

As a stupid idea, also check that both of the decompression levers are fully closed.

 

[Biggles Wader]

Have you looked at the air inlet side? Try removing the air filter and anything else that could restrict air flow and see if it stops the problem.

 

[bignick]

This looks quite useful…

https://www.engineaustralia.com.au/wp-content/uploads/2018/04/SB007.pdf

I don’t quite follow what you meant when you wrote
FYI We dont smoke when at full RPM only when reving the engine.
and no smoke when normally going along.

Please can you clarify?
Full RPM in gear with the boat doing 7kts ish and you don’t get any smoke?

 

[olly_love]

Starting to think of the weird and the wonderful now, because I would have thought the same as you.

Is it getting to correct temp? If it’s running cold you may get more smoke than normal. Running under load can increase temps a bit, but if a thermostat is stuck open then you may have some strange effects.

I think I’d be inclined to empty the tank, replace the filters and fill back up with white diesel from the forecourt. That at least would rule out a batch of dodgy fuel.

I’d also borrow an IR / Laser thermometer and measure temps on the head. (Suspect you may have one.) You may be able to tell if one of the cylinders is running cooler than the other. This may not be anything to do with cooling, but could be an indicator of poor combustion on one cyl.

As a stupid idea, also check that both of the decompression levers are fully closed.

Checked the thermostat, this is opening at 65C as its ment to.
leavers are both down ( checked this one)

we only run on fuel from the petrol station after having alot of water in the fuel on a previous boat.

i will check the temps and see where we end up. but the odd thing is the engine runs smoothly with no miss fireing

 

[olly_love]

This looks quite useful…

https://www.engineaustralia.com.au/wp-content/uploads/2018/04/SB007.pdf

I don’t quite follow what you meant when you wrote
FYI We dont smoke when at full RPM only when reving the engine.
and no smoke when normally going along.

Please can you clarify?
Full RPM in gear with the boat doing 7kts ish and you don’t get any smoke

In neutral ( no gear) or Gear we can rev the engine up and down.

when reving so 800-3200 ish RPM and back we get a big cloud. but normally running along at full RPM we dont get ant smoke through the range.

 

[olly_love]

Have you looked at the air inlet side? Try removing the air filter and anything else that could restrict air flow and see if it stops the problem.

Yes new Filter and also run with it off. and even with the engine box open!

 

[DownWest]

Direct injection diesels tend to smoke a bit when reving up to set speed. The old Lister LR generators that I used to look after were quite smokey (as in lots!) when started, but cleared as soon as they got up to the 1500 rpm running speed.