Bad starting Yammar 2GM20

[Shiver Metimbers]

My boat has the Yammar 2GM20 raw water cooled engine and I have difficulty starting it. Starting the engine on full throttle the engine motors and tries to fire with lots of white smoke, after about 10 seconds it fires on one cylinder but won't run when starter released, keep starter pressed and eventually after about 30 seconds second cylinder fires up and away she goes. Smoke clears virtually immediately, ample power when steaming so don't suspect valve or injection timing. I have done a good service on the engine, Filters, fuel bled through both filters to the pump and injectors, tappets set, injectors serviced. Fitted a new battery this morning and guess what, yep, still the bloody same? I don't have access to a compression tester but turning the engine over by hand it seams to hold it's compression on each cylinder. Has anyone had this problem and a magic cure? Going to take the exhaust elbow and head off tomorrow, will keep you posted.

 

[Tranona]

Before you start taking the head off, check the exhaust hose. Could have collapsed internally causing back pressure. Not always obvious from the outside. Also try with less throttle. My 1GM starts instantly with only a little open.

 

[Shiver Metimbers]

Thanks for that, tried to start in various throttle positions, it will only go on full. Will certainly check the exhaust hose though.

 

[waterbuffalo]

Could be you have a tiny leak in the fuel lines you have not spotted. Then you are priming the engine every time you try to start the engine. Once primed runs OK.

 

[Shiver Metimbers]

Thanks; I can discount this as I tried the bleed point at the pump this morning before starting and got nice clean fuel with no air bubbles, besides lots of white smoke indicates unburnt fuel. Cheers.

 

[freelanderblue]

My 2GM 1999 ran fine when started but was slow to start, also I did not notice any low power when running, would also start on one cylinder then the other and with only full throttle, under took all the clean and tests none proved successful, however the cure involved unblocking the exhaust head /manifold, which had blocked up to with in 10mm of a hole size of 50mm. also replaced the mixing elbow as it had pin holes appearing

The carbon build up was removed with a small Dremel grinder insitu, took me about two hours. now starts well and will rev to a full 3650revs,


Gareth

 

[steve28]

its going to sound odd but try starting on the front cylinder only, decompress the back one, try starting with 3/4 throtttle.

let me know the result.

steve

 

[Peegee]

just had virtually the same problem with my VP2002. Checked everything before eventually removing injectors. They were well carboned up. Had them serviced, with new tips and now good as gold.

 

[SAWDOC]

[ QUOTE ]
Thanks; I can discount this as I tried the bleed point at the pump this morning before starting and got nice clean fuel with no air bubbles, besides lots of white smoke indicates unburnt fuel. Cheers.

[/ QUOTE ]
I started my 2gm20 today just to fire her up with a water supply from a hose pipe. As usual it started first time (neutral gear, no throttle). You should not have to use full throttle. Having established that you have fuel at the pump you could follow the fuel line forward and eliminate any possibility of air blockage further on. The yanmar forum used be very good for topics llike this - I haven't been on for ages so don't know how active it is at present. let us know how you get on.

 

[KenMcCulloch]

I was having somewhat similar problems with my 1GM10 towrads the end of last season. At refit I have found that the exhaust elbow internal bore was greatly reduced due to carbon build-up which is very likely to have been a major cause of difficulty. I am hoping that the engine will start easily when I go back in the water shortly.

 

[steve28]

The main reason for them carboning up at the exhaust elbow and exhaust port is low speed running, it pays to run the engine in gear at near full throttle for 30 mins at least once a trip.

steve

 

[Shiver Metimbers]

Removed the exhaust elbow and it was clean as a whistle, maybe the previous owner has done this as it's been a bad starter with him too, hence the can of easy start (mentioned in previous post) I found in one of the lockers. Removed the head and valves and found all valves and their seats pitted, No2 exhaust valve and seat very badly pitted. Spent a few hours grinding the valves in and now all have good seats and valve faces now. Just waiting for a cylinder head gasket to arrive then the head will be going back on and hopefully this has been the problem?


Valve seats ground in.

Valves built up.

I have checked the bores and they are fine, not glazed and no scrapes or grooves caused by broken piston rings. I left the engine with both pistons mid travel and put the same amount of oil down each one, hopefully the level won't drop or at worst drop slightly and evenly across both cylinders.

 

[pete]

I had a problem with the exhaust valve and seat on my 1GM10. after having the seat recut and a new exhaust valve I regained good compression and the engine started well but after a couple of weeks the problem came back and on removing the head the valve seat had gone again. I removed the head and sent the head to have a new valve seat fitted at a local engineers and he found that when cutting out the old valve seat the bottom of the cut was black metal and on further investigation we found that the head had become porous and assume it was dripping sea water onto the valve seat thus burning it out. I had to bite the bullet and buy a new head but this has solved the problem completely. After I bought the boat I checked the exhaust injection elbow and it was starting to perforate so I replaced it but maybe by then the damage had been done.
Good luck Pete

 

[Shiver Metimbers]

While waiting for the head gasket to arrive I started
to clean the block face ready for the refitting of the head. I have now discovered that No1 piston is lower while at TDC than No2 by 1.3mm. It looks like No1 has a bent Con Rod, oh bugger, that's the engine out!! /forums/images/graemlins/mad.gif

 

[Shiver Metimbers]

I now have the engine stripped down and as suspected No1 Con Rod is bent.

 

[Shiver Metimbers]

When will it end, now found broken piston.