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Old 09-03-2013, 16:51   #1
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Yanmar 3gm30F hard starting and high blowby

So the last few weeks my yanmar 3gm30f has been hard to start. Yes its been cold out. But its harder starting then normal. Seems like one cylinder fires off right away, But then it dies when I let off the starter, maybe after a few seconds, as the other two are not working yet. Its taking 3/4 throttle to really get it going. Then I can hear the other two clyinders start working.

Today after running for hours and after a few hours off, it was again hard starting, where only one cylinder seemed to be turning. This is not normal as it had always started quickly if it had been running that day

Then Yesterday I found out that I have high crankcase pressure. In checking the CCV hose and fittings I found the orifice in the intake manifold plugged, but after cleaning the orifice the crankcase is still building up pressure with the hose attached.

One last test: I started it up and at idle opened the decompression lever for each cylinder. #2 and #3 sounded about the same (rough idle with a knock with level pulled) but #1 did not make much difference. (No knocking at all).

The engine only has maybe 1000 hours on it.

I'm thinking that #1 injector might not be working very well if at all. Will be looking at that the next few days.

When running it runs fine and runs up to 3400 rpm in forward. A bit more in reverse.

I'm worried that the high blowby is due to wore or more likely a broken ring. Please tell me it ain't so.....

Coolent level is fine. Oil had been going down some but that could have been from high crankcase pressure sending oil down the guides.

I had just changed the oil and filter a week or so ago. Everything was fine then..

Thoughts.
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Old 09-03-2013, 17:11   #2
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Re: Yanmar 3gm30F hard starting and high blowby

Injector rebuild and compression test are where you need to start. Good luck. Any chance you can get the loan/rental of a leak down kit?

Oh, any possibility of water in the fuel?

Good luck...
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Old 09-03-2013, 17:14   #3
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Re: Yanmar 3gm30F hard starting and high blowby

Cheep method of test is to buy some injector washers and trade the number 1 injector with another one and see if the decompression test follows the injector or still is on number 1 cylinder. If the miss follows the injector, have it rebuilt. If it stays on number 1 expect large sums of money to be spent.____Good Luck____Grant.
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Old 10-03-2013, 10:23   #4
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Re: Yanmar 3gm30F hard starting and high blowby

I hope you haven't burned a hole in the piston, another potential cause of oil loss.
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Old 10-03-2013, 11:25   #5
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Re: Yanmar 3gm30F hard starting and high blowby

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I hope you haven't burned a hole in the piston, another potential cause of oil loss.
I don't think so. The engine once started runs well and sounds fine. No oil/fuel in the exhaust, etc. I was thinking last night that I don't know how much bypass a diesel should have. With the small orifice in the intake manifold, I'm thinking yanmar wanted positive crankcase pressure....

I'm thinking as I don't have money to fix it if its serious, that I'm going to let it ride until it dies. From what I gleamed on other diesel sites, it can run another 1000 hours or so like this., if it is bad rings

As the end result is the same money wise, I'm going to just relax. Besides if the engine does die, I may just junk it, get a long sweep oar and go sailing.....
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Old 10-03-2013, 11:53   #6
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My boat, recently purchased, has the same engine and when the cold weather hit the engine went from a quick start, (throttle at idle), to hard starting. I talked to a mechanic at List Marine Services in Sausalito and he recommended setting the throttle to 3/4 for starting the engine, regardless of the weather. It seems to work. I hope you problem is as simple to fix...

Regards
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Old 10-03-2013, 11:58   #7
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Re: Yanmar 3gm30F hard starting and high blowby

Sounds like the 3GM30 I had that had a broken piston ring land. Hard starting, sounded fine at high rpm. No other symptoms, no smoke, no burning oil... juts real hard starting...Incidentally these engines (catamaran) were built in the early 90's and both failed prematurely. The first one at 800 hours. It took me 3 mechanics to find the issue. I debated with him but he was right! I dont know why some mechanics tell you to run them at 3500 rpm!
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Old 12-03-2013, 16:18   #8
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Re: Yanmar 3gm30F hard starting and high blowby

OK did a little more testing. The engine is hard starting cold and also hot. I got it started today by pulling #1 decompression lever. Do that and it will start on the other two cylinders. If I close the decompression lever on #1 right after it starts the engine will die. If I wait 20-30 seconds, it runs and after a few second or so I hear the cylinder pick up. However found out today that even hot I have the same problem.

Once it runs and warmed up it will pull to 3500 Rpm with prop engaged in reverse. No unburnt fuel in water. I may be slightly overproped as when moving it will pull 3200-3300 rpm forward

I'm wondering if maybe the fuel lift pump or a partly clogged discharge ell could be the problem. Think the discharge ell would cause excessive back pressure too.

Going to check that the next few days. It does sound like #1 takes a long time to fire, that is get fuel to the cylinder....
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Old 12-03-2013, 18:49   #9
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Re: Yanmar 3gm30F hard starting and high blowby

Next cheapest test, Pull #1 injector and take it to an injection shop and have it POP TESTED. That will tell you right away if it is the injector or something more complicated. If 2 cylinders start reliably, I would not worry about the lift pump. If it is only the injector, but you run it for a long time, you could do more serious damage to the engine. Do the cheapest things first.____Grant.
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Old 12-03-2013, 18:54   #10
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Re: Yanmar 3gm30F hard starting and high blowby

High blowby, burning oil, hard to start. That all sounds like low compression, doesn't it?
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Old 12-03-2013, 19:14   #11
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Re: Yanmar 3gm30F hard starting and high blowby

So the answer to the question to why my engine was hard starting and had low compression on #1 was.......

OK I was going to pull the #1 injector and take a look at it. As I started loosening the nuts I found that one nut was a little loose and the other was way loose, over a turn.

So after checking the other two injectors, which were both tight, I tighten up the hold down nuts on #1 injector. Turned the key and the little bugger started right up...

I'm hoping the blowby issue will solve its self with the hot #1 cylinder. In any event I think I've found my starting issue. Least wise its starting far far easier now...
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Old 12-03-2013, 19:40   #12
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Re: Yanmar 3gm30F hard starting and high blowby

Isnt it wonderful when a potential disaster is solved with a little effort!!!. I would clean around the number 1 injector to see if the leaking might have cut a groove in the copper washer. Just watch it for a while. I know there is a lot of debate on how to run diesels, but I would not run that poor old beast at 3500 RPM except in an emergency. Glad to see an easy solution. ____Grant.
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Old 12-03-2013, 19:47   #13
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Re: Yanmar 3gm30F hard starting and high blowby

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Isnt it wonderful when a potential disaster is solved with a little effort!!!. I would clean around the number 1 injector to see if the leaking might have cut a groove in the copper washer. Just watch it for a while. I know there is a lot of debate on how to run diesels, but I would not run that poor old beast at 3500 RPM except in an emergency. Glad to see an easy solution. ____Grant.
Oh except for testing in gear now and then, I don't even come close to 3500 rpm. Most of the time I'm down at 2000 to 2500 rpm. Really the 3gm is almost too much engine for my little boat.. 2200 rpm is where its happy most of the time...
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Old 12-03-2013, 20:21   #14
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Re: Yanmar 3gm30F hard starting and high blowby

Good job Chic
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Old 12-03-2013, 20:41   #15
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Re: Yanmar 3gm30F hard starting and high blowby

Great trouble shooting!! it's just like when the won't turn over properly! ya ck the batt conections first! When they won't run right ya ck the fuel delivery system for leaks and looseness! works almost every time !! Great job! ya see you almost never need any help from what Ive read on here !! Just sayin ya do great !!
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