Yanmar 1GM10 starting issue

[shanti_83]

Hello everybody!

I hope somebody can give me some advice here, or maybe have experienced the same problem.

I have a Yanmar 1GM10 with a problem when cold starting. This only occurs when the engine has not been recently used. The moment after starting it, everything sounds ok, but then it gradually slows down and runs very slowly or heavily for a while. It kind of sounds like knocking, really not good. There is lots of black smoke and (I think) very little cooling water coming out. If I move the throttle, nothing happens, it just runs in the same slow speed. After a while, maybe 30 seconds or more, it suddenly picks up and runs normally. The cooling water then coming out is completely black and probably full of oil, I guess. It leaves a nice film on the water surface around it...

I have tried to increase the throttle when starting it, this worked for a while, but lately the problem have started again.

I know there is probably many things that can cause this, but I have no idea where to start looking..

It would be nice to hear if somebody had a similar problem and managed to fix it, but I am very thankful for any help!

 

[RichardS]

The very first and simplest thing to do is to remove the exhaust elbow and check that it is not blocked with carbon deposits from the exhaust.

Richard

 

[shanti_83]

The very first and simplest thing to do is to remove the exhaust elbow and check that it is not blocked with carbon deposits from the exhaust.

Richard

That is one thing I was thinking about doing actually... Thanks for the tip!

 

[pete]

My previous boat had a 1GM10, It started throwing sooty oily deposits out of the exhaust mainly under high revs followed by bad starting. We found out it was due to exhaust valve not sealing so poor compression. We fitted a new valve and lapped it in which solved the problem temporarily, but it happened again, turned out that the head had become porous possibly due to the exhaust bend perforating internally and seawater was dripping directly on to the exhaust valve seat. A new head and exhaust bend solved the problem, hopefully yours hasn't come to that.

 

[shanti_83]

Ok, I hope this is not the case for my engine... it sounds a bit expensive as well! Anyway, it doesn't have this problem when running, it is only when starting. Thanks for the input!

 

[Topcat47]

Top end overhauls don’t usually involve new valves. Yanmar spares aren’t cheap and you would need a set of gaskets. Keeping the tappets set and the valves sealed pays dividends as these wee engines are not the best starters.

 

[LiftyK]

Has anything happened to your alternator or charging arrangements recently? I had similar starting problems when I replaced my alternator with a clone. It had a different size pulley to the original, placed extra load on the engine especially at startup and it struggled to keep running until the alternator load reduced or the engine warmed up. Repairing and refitting the original alternator was an instant cure. Do think about alternator load as a potential cause of rough cold starting if anything has changed to trigger that.

 

[Topcat47]

+1 re the alternator. I bought a cheap chinese copy rated the same as the OEM Hitachi but in fact producing around twice the current. The cold engine wasn't able to swing it. Replacing the pulley might have done something but the Hitachi pulley didn't fit the armature of the replacement. This only matters If you're trying to run a new replacement alternator. If the engine starting problem is recent and the alternator is OEM, then look to a top end overhaul. I know about the "bent con rod" argument but if the piston aligns with the top of the cylinder when the head's off, it's not a bent con-rod. Another head problem may be the holes in the pre-combustion chamber are coked up. Depending on the age and engine hours, it might be an idea to remove the injector and pump for a clean and refit by an automotive diesel specialist. It's something I do roughly every 5 or 6 years.

 

[garymalmgren]

Hi Shanti
Lets run through your symptoms.

I hope somebody can give me some advice here, or maybe have experienced the same problem.

I have a Yanmar 1GM10 with a problem when cold starting. This only occurs when the engine has not been recently used. The moment after starting it, everything sounds ok, but then it gradually slows down and runs very slowly or heavily for a while. It kind of sounds like knocking, really not good. There is lots of black smoke and (I think) very little cooling water coming out. If I move the throttle, nothing happens, it just runs in the same slow speed. After a while, maybe 30 seconds or more, it suddenly picks up and runs normally. The cooling water then coming out is completely black and probably full of oil, I guess. It leaves a nice film on the water surface around it...

I have tried to increase the throttle when starting it, this worked for a while, but lately the problem have started again.

I know there is probably many things that can cause this, but I have no idea where to start looking..

It would be nice to hear if somebody had a similar problem and managed to fix it, but I am very thankful for any help!

1. The moment after starting it, everything sounds ok,
Does that means it cranks over and starts properly after a few seconds of cranking?

2. but then it gradually slows down and runs very slowly or heavily for a while.
That would indicate fuel starvation.

3. It kind of sounds like knocking, really not good.
Small diesel engines will knock if run really slowly. It is called ignition/detonation knocking.
Does the knocking stop when the revs pick up? If so, this is not a worry.

4. There is lots of black smoke and (I think) very little cooling water coming out.
The lack of cooling water would be from the very low revolutions. The amount of exhaust water is proportional to the speed of the water pump rotations. The black smoke usually indicates unburnt fuel.

5 If I move the throttle, nothing happens
Again this would indicate a problem with fuel supply.

6 . After a while, maybe 30 seconds or more, it suddenly picks up and runs normally
This would indicate that the problem is transitionary. (i.e. Not fixed or permanent, which is a hopeful sign)

7 .The cooling water then coming out is completely black and probably full of oil
That oil is probably unburnt fuel.

Some Suggestions.
Do you have a service manual? If not, chase a free one down on the net.
Have you changed the fuel filters recently? If not change filters and re-bleed fuel system.

best of luck
gary

 

[shanti_83]

Has anything happened to your alternator or charging arrangements recently? I had similar starting problems when I replaced my alternator with a clone. It had a different size pulley to the original, placed extra load on the engine especially at startup and it struggled to keep running until the alternator load reduced or the engine warmed up. Repairing and refitting the original alternator was an instant cure. Do think about alternator load as a potential cause of rough cold starting if anything has changed to trigger that.

No, I haven't made any changes to the alternator since I bought the boat 3 years ago. But this engine start up problem has been there all 3 years, not all the time, but sometimes. I do actually remember that I once removed the alternator belt and tried to start the engine without it, it started without any problems then. Not sure if it has anything to do with it though, because sometimes the engine starts without any problem. Anyway, thanks for the suggestion!

 

[shanti_83]

Thank you for the run through, Gary!

To answer your questions:

1. The moment after starting it, everything sounds ok,
Does that means it cranks over and starts properly after a few seconds of cranking?

Yes, it does start properly, and then slows down just after starting.

3. It kind of sounds like knocking, really not good.
Small diesel engines will knock if run really slowly. It is called ignition/detonation knocking.
Does the knocking stop when the revs pick up? If so, this is not a worry.

Yes, the knocking stops when the revs pick up, so it's probably just because of the slow speed.

So yes, it must probably have something to do with the fuel supply. I have recently checked my filters, and they are ok.

As suggested by Topcat47, it might have something to do with the injector or injector timing. I am going to have a look at that...

Thank you for your anwers everyone

 

[LiftyK]

No, I haven't made any changes to the alternator since I bought the boat 3 years ago. But this engine start up problem has been there all 3 years, not all the time, but sometimes. I do actually remember that I once removed the alternator belt and tried to start the engine without it, it started without any problems then. Not sure if it has anything to do with it though, because sometimes the engine starts without any problem. Anyway, thanks for the suggestion!

If the engine has always been like this since you had it then it could well be alternator load. May I add that the symptoms of a) spluttering b) loads of black stuff coming out of the exhaust c) varying throttle making no difference are identical to what I had.

 

[jamie N]

I do actually remember that I once removed the alternator belt and tried to start the engine without it, it started without any problems then. Not sure if it has anything to do with it though, because sometimes the engine starts without any problem. Anyway, thanks for the suggestion!

Could it be an idea to put a switch into the alternator circuit? The switch isolates the exciter circuit, until the engine is up to speed, and running in a 'confident' manner, at which point the switch is engaged and the alternator is connected and under load.
It's a very simple mod, and on low power engines does eliminate any superfluous immediate power requirements, overloading the engine on startup.
My previous and present engine's both have had this, and I do feel that it's beneficial.

 

[Tranona]

As suggested by Topcat47, it might have something to do with the injector or injector timing. I am going to have a look at that...

Thank you for your anwers everyone

The timing is fixed at the factory using shims under the pump. Be careful if you do remove the pump that you don't damage the shims. I installed a 1GM in 1992 and sold it in 2009 to go into another boat. Never removed the injector all that time and AFAIK the engine is still giving good service.

Your symptoms do lead to overloading from the alternator drive and the smoke is unburnt fuel from incomplete combustion. The low water output is because the engine (and pump) is turning so slowly for those few seconds. The engine produces little power at low revs and any overload will prevent it from picking up until it gets hot enough and picks up as you describe. You may find it helpful if it has stood for a while to turn it over with the decompression lever raised as this will circulate oil helping seal the rings and so increase compression. Then open the control lever almost fully to give extra fuel on start, pulling back as soon as it fires.

If it runs OK otherwise and you can get full revs under load, would not worry too much about the odd starting behaviour.

 

[shanti_83]

Just a little update here... So the last two times I have started the engine, I have primed the fuel pump a few times before starting, and the engine started running normally right away! I guess that means there might be a problem with compression... I'm going to wait a few weeks until the season is over, and then see if I can do some maintenance/service on the engine.

 

[Boater Sam]

Just a little update here... So the last two times I have started the engine, I have primed the fuel pump a few times before starting, and the engine started running normally right away! I guess that means there might be a problem with compression... I'm going to wait a few weeks until the season is over, and then see if I can do some maintenance/service on the engine.

That would suggest a fuel drainage problem rather than cylinder compression. Is there a lift pump with non return valves?

 

[LiftyK]

Just a little update here... So the last two times I have started the engine, I have primed the fuel pump a few times before starting, and the engine started running normally right away! I guess that means there might be a problem with compression... I'm going to wait a few weeks until the season is over, and then see if I can do some maintenance/service on the engine.

That’s promising. I hope your servicing uncovers the cause of your intermittent starting issue. I would mention that my ancient 1GM10 starts best at idle throttle and without priming, even in Spring after sitting still all winter. Push the starter button and it bursts into life without hesitation. If yours doesn’t do that then I am sure something needs to be tweaked.

 

[.30-30]

New to 1GM10 and have to share this. I was victimized by a new alternator, and, after reading the initial post though I was reading something I could have posted. My replacement alternator at first did not charge until 3500 rom, which is to say, did not charge on the boat. The next one started charging full on after start. That is where the same the the symptoms showed up, and it took me a month to find these posts, to then remove the belt and witness proper starting, immediately.
Thank you all for contributing.