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Old 27-05-2015, 05:42   #1
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hard starting a yanmar20gm

i have been having trouble starting my engine. ( yanmar 20gm) i have a 1974 morgan out island 28'. i bought it 4 months ago. when i first started it would start . then the starter would turn over very hard like it wouldn't start. i started using ether. that helped a bit.then it would start and than not. now it won't start at all. i have checked the starter it's ok than the batterys no start. now i have about 1,000 cranking amps no start . i checked the injectors to see if i was getting water in the chamber no. i have been told that it's the head gasket. before i go any further i want to make sure before i tear it down. i also bled all the fuel lines from tank to injector. i am very new to diesel engines but i have worked on many gas engines so i do have some experance on engines.
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Old 27-05-2015, 07:01   #2
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Re: hard starting a yanmar20gm

Don't use ether, it's terrible for your engine. It will eat away at the piston crown and destroy your rings.

Have you changed your fuel filters since you bought the boat? Check your air filter too. If everything looks good there, check compression.

You say you've been told it is your head gasket. Who told you that and what led them to that conclusion?

These little Yanmars are pretty simple. All you need is clean fuel, air, and compression. Hope some of this helps.
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Old 27-05-2015, 07:53   #3
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Re: hard starting a yanmar20gm

^^ +1.

With air, clean fuel getting delivered into the cylinder and compression, these engines will start.
All of these items can be checked without tearing the engine apart.
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Old 27-05-2015, 15:24   #4
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Re: hard starting a yanmar20gm

It would be cheaper to have a diesel mechanic check out the motor than tear it down if that's not needed. A compression test would tell much. Starting fluid greatly increases compression and it's need could indicate low compression. It also breaks rings when used too heavily and then it is needed until overhaul. A block heater will often get a balky diesel to start in cold climates.
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Old 28-05-2015, 09:12   #5
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Re: hard starting a yanmar20gm

had the same proplem, yanmar dealer sold me a starter jump cylinoid. cured the problem 6 yr ago and now now starts with only 10 volts in battery. it buypasses lots of electrical load that goes thru the wiring harness. I did not use the wire from the kit as I had plenty of much larger marine wire from a rewire, solodered and shrinked wrapped all fittings with some kind of waterproof gunk that they told me to use. GREAT FIX
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Old 28-05-2015, 09:19   #6
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Re: hard starting a yanmar20gm

Does it turn over and not start?
Check to make sure your exhaust elbow is not clogged.
Had that happen to me several years ago. Went through all sorts of gyrations to figure out why it wouldn't start - head gasket, injectors, fuel filters, air filter, etc., etc., etc. Finally figured out it was the elbow. Purchased a new one, installed it. Engine started right up!!!!!!
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Old 28-05-2015, 09:29   #7
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Re: hard starting a yanmar20gm

If you MUST use fluid, use wd40 in tiny little spritzes.At least it will lube the top end instead of drying it out.If you slip the boat, install block heater. Warm mass of metal will start easier than cold hunk of engine.If you have glow plug (s), DON'T use starting fluid, no matter HOW desperately you want to start the iron monster!
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Old 28-05-2015, 09:57   #8
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Re: hard starting a yanmar20gm

Quote:
Originally Posted by jchock View Post
i have been having trouble starting my engine. ( yanmar 20gm) i have a 1974 morgan out island 28'. i bought it 4 months ago. when i first started it would start . then the starter would turn over very hard like it wouldn't start. i started using ether. that helped a bit.then it would start and than not. now it won't start at all. i have checked the starter it's ok than the batterys no start. now i have about 1,000 cranking amps no start . i checked the injectors to see if i was getting water in the chamber no. i have been told that it's the head gasket. before i go any further i want to make sure before i tear it down. i also bled all the fuel lines from tank to injector. i am very new to diesel engines but i have worked on many gas engines so i do have some experance on engines.
Ether bad. The engine gets addicted to it. Mainly because its so good at removing all lubrication.

It should never be used on a diesel due to runaway.

Most diesel problems are fuel related. What diagnosis have you performed.

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Old 28-05-2015, 10:17   #9
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Re: hard starting a yanmar20gm

I'm confused... does it turn over well and rapidly but not start? If so I would check the compression. (have it checked)
If it turns over slow, you need to test your starter cable connections etc. Including the ground to the motor chassis. Could be the starter too if those get cleaned and no love.


It could be a lot of things if it turns over well. If it's a 2GM20 those engines are famous for piston issues also.
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Old 28-05-2015, 12:56   #10
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Re: hard starting a yanmar20gm

New head gasket solved my no start problem. 1gm10

Check your compression.
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Old 28-05-2015, 13:55   #11
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Re: hard starting a yanmar20gm

If the starter is turning the engine over slowly when you have a well charged and good battery then it might be the starter. I had to have one rebuilt because it was just plain shorting out. It would turn the engine over but not fast enough.

Do you have compression release on your engine?

Have you checked the exhaust as well as the clean diesel.

You say you have bled the fuel lines but did you bleed them enough to get it to fire?

Just so many questions.
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Old 28-05-2015, 16:45   #12
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Re: hard starting a yanmar20gm

I would remove injectors & with them hooked up crank the engine over with the starter & decompression lever engaged & check they spray properly. If they do then check compression & exhaust elbow. A trick I use is to dribble a little engine oil in the air intake before starting if the compression is suspect & if it fires right up you can be reasonably sure it's a compression problem. In fact I need to do this to start my Yanmar YSM8 & I know the compression is below spec. Dont put too much oil in as you will bend a pushrod ( I did) or worse, I'd say about a teaspoon of oil. Far better to do a compression test if you can as this procedure is risky although I have been doing it for months. I just hammered the pushrod straight & it's been working fine.
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Old 28-05-2015, 17:35   #13
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Re: hard starting a yanmar20gm

Would almost guarantee if ether has been used then the ring land is broken on one piston. Little engines are too small for ether. Check to see if after running the oil level seems to have risen a little bit. Fuel will leak past the rings in the broken land and end up in the oil, this thins the oil and makes it even harder to start as there is less compression with the thinner oil. Changing the oil will help it start a little better in a pinch but there is only one way to fix it. About an hour will pull the head to verify. Good luck.
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