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Old 31-01-2020, 21:00   #1
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Hard to start

I need advise please. My 2GM20 Yanmar motor is slow to fire up. The longer it has not run the longer it takes to fire up. I decompress it and turn it over until it's rolling fast, then recompress whilst still rolling over. I do this until she eventually fire and she will then start. This could be as long as 10 minute.
Why wont she fire up quickly?
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Old 01-02-2020, 00:23   #2
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Re: Hard to start

First a belated welcome to CF burleigh66, clearly you have been reading for a long time and so it is nice to see your first post.

The are only a few reasons a 2GM20 won't start easily.
No air
No compression
No fuel

Usually the air is not a problem but a blocked exhaust can cause poor air induction.

You haven't given us much background on the engine like age, hours, how well it runs after starting so the following is therefore generic in nature and you will have to work out if it applies to your situation.

First assumption - you are using the starter motor - not hand cranking!

As you are using the decompression method of starting, I am going to assume you have a weak battery or a problem with the battery wiring to the starter motor. Normally with everything working properly, you don't need to decompress a 2GM20 to start. In fact, it should start within a couple of revolutions i.e. less than 1 second and 2 or 3 at the very most.

Slow cranking when starting results in low compression when starting.

Will the engine spin over rapidly with the starter motor without being decompressed? If not, fix the starting circuit. It could be a weak battery, poor battery cables, poor terminations, problems with the wiring harness (sort of common on older Yanmars) or less likely a dodgy starter motor.

If it does spin over well but won't start, then air in the fuel seems likely. Replace the fuel filters and bleed the fuel system. It's not hard once you know how.

Another possibility for low compression is zero (or negative) valve lash. Easy to check the tappet clearance. It should be 0.8mm or 12 thou (IIRC).

Finally check the exhaust manifold / mixing point for carbon build up.

There could be other reasons but most are unlikely, especially if the engine is running OK after starting. That is, it delivers power OK and doesn't blow clouds of smoke!
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Old 01-02-2020, 02:28   #3
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Re: Hard to start

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Originally Posted by burleigh66 View Post
I need advise please. My 2GM20 Yanmar motor is slow to fire up. The longer it has not run the longer it takes to fire up. I decompress it and turn it over until it's rolling fast, then recompress whilst still rolling over. I do this until she eventually fire and she will then start. This could be as long as 10 minute.
Why wont she fire up quickly?

When I had that it was a loose capacitor but it might br something else.
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Old 01-02-2020, 03:09   #4
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Re: Hard to start

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When I had that it was a loose capacitor but it might br something else.

Sorry that should be loose Solenoid
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Old 01-02-2020, 06:46   #5
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Re: Hard to start

The feeling I get from your description is that you mean that it takes longer to start if the engine sat for a month than it does if it sat for a week. If this is the case, then you likely have a 'leak down' situation, where the fuel drains back into the tank, and the lift pump has to rebuild pressure to the injection pump. This could be caused by loose fittings, old leaky (semipermeable) lines, loose hose clamps, loose or leaky filters or filter seals, worn primer components (if fitted) etc.

Otherwise, see Wotname's post.
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Old 01-02-2020, 12:35   #6
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Re: Hard to start

Thank you all so much for your replies.
I will start with checking the battery, leads, connections, volt leakages and then solenoid.
If this does not fix my problem I check the exhaust and look for air leakage in the fuel system and check the fuel pump ect.

Safe sailing everyone.
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Old 02-02-2020, 21:03   #7
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Re: Hard to start

Quote:
Originally Posted by jimbunyard View Post
The feeling I get from your description is that you mean that it takes longer to start if the engine sat for a month than it does if it sat for a week. If this is the case, then you likely have a 'leak down' situation, where the fuel drains back into the tank, and the lift pump has to rebuild pressure to the injection pump. This could be caused by loose fittings, old leaky (semipermeable) lines, loose hose clamps, loose or leaky filters or filter seals, worn primer components (if fitted) etc.......
You make an astute point jimbunyard.



And to my mind, this is the beauty of CF; someone always has an insightful post on most subject matter.
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Old 18-05-2020, 23:40   #8
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Re: Hard to start

thanks everyone for your comments. at the end of the day I up graded my battery to a 850cca and this has improved the time it takes to start. I am still using the decompression to spin the motor but she kicks in in a relatively short time.
Cheers everyone
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Old 19-05-2020, 12:24   #9
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Re: Hard to start

A leaky diaphram in the lift pump can also contribute to this issue, as can valves needing to be lapped and lash adjusted.
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