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Old 16-11-2012, 05:45   #1
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Yanmar 2gm20 fwc

On Long Island,ny when it gets cold 40/50 engine hard starting. When it does start vibration and valve tapping sound increase rpm to 1400 and it starts to smooth down till warm but still has some vibration
Have not checked valve spacing, no change when oil is new or not, no change with synthetic or regular oil, problem seems to be getting worse with time.
The colder it gets, the harder to start...starting battery needed help with big house battery. The charging voltage 14
Any good news out there
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Old 16-11-2012, 06:56   #2
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Re: Yanmar 2gm20 fwc

Hard starting is most likely low compression or a poor injector spray pattern. Replace the injectors firstt. They cost about $100 each.

David
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Old 16-11-2012, 07:02   #3
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Re: Yanmar 2gm20 fwc

why not check the compression before replacing injectors?
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Old 16-11-2012, 09:02   #4
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Re: Yanmar 2gm20 fwc

You can replace the injectors yourself. You will probably need a mechanic to check compression as it takes a gauge and the right fittings for the injector hole. It is all a matter of which is cheaper. When you pull the injectors to check compression, I would replace them then unless you know they have less than 1000 hours on them.

Also a shadetree blowby test is another way to check compression. Disconnect the vent hose from the top of the rocker arm cover. Run the engine in gear up to 2,000 rpm and feel for blowby from the hose. A little is ok, lots is bad. I know this is subjective and it takes experience to tell good from bad. But give it a try. It is cheap and easy to do.

One thing I didn't say and should have, is that the clattering at low rpm also suggests a poor injector spray pattern. The diesel doesn't burn smoothly due to the poor pattern, therefore the clatter.

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Old 19-12-2012, 15:58   #5
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Ok tested compression with special tool compression at 420 psi each cylinder

Took out injectors for cleaning and repair
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Old 19-12-2012, 16:12   #6
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Re: Yanmar 2gm20 fwc

Some engines injectors wear differently to others in respect to spring sag, ie, the spring that provides the correct cracking pressure (point of injector opening) loses it's spring strength.
This causes a few issues.
Firstly, the spray pattern is not as finely atomised which means bigger droplets instead of a mist and that takes longer to burn as it has to burn each of these bigger drops right thru from the outside to the inside.
Secondly, as the cracking pressure is what controls engine timing (unless you are late model computer controlled) the injector will open earlier than normal. With the fuel in the engine too early it is firing before it is meant to and working againsty the direction of engine rotation for a millisecond. Advanced injection can also cause 'pinking' not pinging.
You will also use more fuel and blow more smoke.

Injector service is a regular maintenance thing and can make huge improvements to engine life and performane.

Tappet clearance is also important as that determines the timing of the camshaft to a small degree, eg, tight tappet opens earlier.
I have worked on engines that shook like a dog sh**ting razor blades that ran smooth as silk after a tappet adjustment.
It's free and easy to do, at worst it might cost a new rocker cover gasket.

I think you are taking the right course of action.

Old boss once said, "son, it costs just as much to rebuild a half stuffed engine properly as it does to rebuild a stuffed one."

Cheers
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Old 19-12-2012, 16:36   #7
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A good battery is very important. Yanmar needs a good fast strong crank. When mine is cold or has not been started for awhile I open the decompression levers give it a little throttel and crank it a couple of times. Then close the lever and crank. Starts right up. I feel it gets the oil and fuel going. Works for me.
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Old 19-12-2012, 16:44   #8
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Re: Yanmar 2gm20 fwc

Good call badsanta,
always a good way to treat you engine. Allowing a cushion of oil between the bearing shells and crankshaft before being subject to insane pressure.

Highly recommended for engines that haven't been started for a while too. Often engines with hydraulic lifters will run noticeably quieter if primed as Santa said.
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Old 19-12-2012, 17:49   #9
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Re: Yanmar 2gm20 fwc

If you are in a slip with shore power there are heating pads that glue onto the bottom of your oil pan and keep the oil warm. This can help a great deal on engines that don't have glow plugs. Also if you have decompression levers on your engine, spin the engine with the fuel shut off then open fuel and shut the decompression levers at the same time.

I have a feeling though that injector rebuilds will help a lot. A cetane booster might also help, but it has to be mixed thoroughly with the fuel in the tank so it is best added when you refill.
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Old 09-03-2013, 07:28   #10
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Smile Re: Yanmar 2gm20 fwc

Sorry for the delay in responding...cleaned the injectors and replaced with new seals, temperature of engine and day was 34 degrees..purged air from lines..tightened the fuel lines proceeded to start engine and......within four revolutions it started and ran, something it would never do. Shut it down and will wait for spring.
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