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Old 02-10-2012, 06:08   #16
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If fuel is draining back down the line then you have to refill the system.
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Old 02-10-2012, 08:27   #17
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Re: Yanmar 3GM 30 Hard Starting

Well, my last post yesterday went AWOL, so I'll try again.

I tried a crude compression test that I just read of: try rotating crankshaft with 2 cylinders at the time decompressed to compare and evaluate compression resistance. Was told that this could be done with some difficulty, and that's what I found. So I think compression is OK. Allowed me to go to next step, where I suspect the problem is, removing and testing the injectors.

First pulled out easily. Second with difficulty. Third wants to stay there. I have retreated.

Anyone have any suggestions or know of a special tool/puller? I see that there are flats on the injector that perhaps a crowfoot wrench could fit and give it a little twist. Didn't notice or explore this option last night (because I didn't have one anyway), but I hope there is room for one. Looks like 24 mm, which sounds unusual, and 15/16" might be closer.
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Old 02-10-2012, 19:31   #18
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Just losen the nuts on the injector do not remove them. Then crank the engine and it should pop up. If you remove the bolts your injector will come shooting out and you may loose it or put your eye out.
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Old 03-10-2012, 01:10   #19
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Quote:
Originally Posted by ScuzzMonkey
Just happened across this thread and got very curious as I have been having a similar problem recently with my 3GM30.

Something that no one else has mentioned, however, is whether they are having a hard start every time, or only sometimes?

On mine, it starts hard the first time I start it on a given day. After that, it starts up normally and easily.

I thought at first that it was simply having trouble with a cold start, but that's not it... although it will start easily if warm, it starts equally easily when cold (after, say, eight hours of sailing). But let it sit for a day or two, and it's a hard start all over again.

Thought at first it was the stop knob, as someone mentioned, but I've been checking it closely since this started and that doesn't appear to be it.

So, does that sound like the compression problem, or something else? I am guessing it could be, since if David is correct about the fuel sealing the rings during the first start, it might continue to seal them for some hours later but have evaporated/pooled by the next day. I'll definitely pull the hose and check for blow by.

On the other hand, like ggray, I don't notice any particular drop off in power once it has started, even under heavy load, which is something I've always heard associated with compression problems.

Anyway, glad to find this thread, appreciate any feedback anyone might have on the hard first start/easy the rest of the day phenomena!
Hmmm if I'm the David quoted as saying "the fuel sealing the rings" I didn't mean that. My original owners manual specifies the throttle position when starting so itmismhard for me to imagine that diesel is going to create the kind lf seal necessary to fire off a cold engine. I could be dead wrong.

Earlier this year I was very concerned about our engine condition. Hard starts from cold; preheater, crank crank, fire, black cloud, Captain complaining. You get the picture. easier starts from warm but I always held my breath.

Over the summer we motored a lot; upward of 15 - 20 hrs in some nasty conditions. Because I was getting fussed about the engine, I was tried a fuel injector cleaner with a cetane booster. I ran through 20 gals of fuel treated with this stuff ( I can't remember the name but will take a photo of the container this weekend). Long story made some what short? She now runs better than ever, starts easily using the exact start procedure and the is no need to use the preheat.

My conclusion? I had some dirty injectors that we're not atomizing the fuel sufficiently. Perhaps the cetane boost makes a difference but if so the it is really amazing stuff based on the difference from the spring and now.
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Old 03-10-2012, 01:13   #20
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Whoops sorry I was the wrong Dave...
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Old 03-10-2012, 07:24   #21
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Re: Yanmar 3GM 30 Hard Starting

You are, but thanks for the tip to try the injector cleaner.

I shared your skepticism about the seal and the forces involved, but I've done enough forum reading since then to believe that indeed, something happens to allow engines with compression problems to start after the fuel gets flowing.

A trick mentioned elsewhere that I haven't seen in this thread yet is to crank for 15-20 seconds, then let it sit for a minute, then hit the starter again. That works on the same theory and a lot of folks report success (although the underlying problem is obviously only going to get worse).

But I'm still not sure compression is my problem and the more I read the less I know! I'm back to thinking it might be air in the fuel line. The surveyor reported a leak at the primary filter; I still haven't been able to locate it, but if he was correct, then from what I understand that could lead to similar symptoms.

Unfortunately won't have a chance to check most of this stuff until next month, but this has still been an excellent thread for things to try.
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Old 03-10-2012, 08:36   #22
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Re: Yanmar 3GM 30 Hard Starting

Quote:
Originally Posted by TheOffice View Post
If fuel is draining back down the line then you have to refill the system.
I like this prospect. I have the same symptoms. Hard starting after a day or more of no use.

Next time I'll prime the fuel system with the squeeze bulb before I hit the starter to see if it makes a difference.
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Old 03-10-2012, 09:59   #23
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Re: Yanmar 3GM 30 Hard Starting

Ggray, if you have checked your cylinder compression,leaks in the fuel pathway to the injectors(check the connections to your lift pump and primary and secondary fuel filters), fuel quality and injectors and everything is fine, there is one last area that could cause the problem--injection pump. I had the identical problem and replaced the injectors, cleaned and treated the fuel and it still barely started with smoke on ignition. There are seals and check valves in the injection pump that go bad and allow drain back of fuel from the cylinders. If you haven't rebuilt your pump, it would be my next step before calling a mechanic. My pump rebuild cost about $250. from a certfied injection shop and it is not difficult to remove/install. My engine has started perfectly ever since. Hope that helps. Good luck and good sailing.
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Old 03-10-2012, 10:14   #24
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Re: Yanmar 3GM 30 Hard Starting

I had that exact problem on the same engine. After 3 mechanics etc, we discovered that one ring land on one piston was cracked... just floating in there. Evidently this is not uncommon on the older GM series...
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Old 03-10-2012, 19:36   #25
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Re: Yanmar 3GM 30 Hard Starting

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Originally Posted by Cheechako View Post
I had that exact problem on the same engine. After 3 mechanics etc, we discovered that one ring land on one piston was cracked... just floating in there. Evidently this is not uncommon on the older GM series...
So, since I'm in the same neck of the woods, would you be comfortable posting the name of the golden mechanic who figured it out, so I can avoid going through the first two myself?
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Old 03-10-2012, 19:57   #26
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Re: Yanmar 3GM 30 Hard Starting

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Originally Posted by ggray View Post
Anyone have any suggestions or know of a special tool/puller?
If you don't already have them out (since I am late returning to this thread), and if you don't want to crank the engine to blow them out, diesel mechanics have a slide hammer puller that screws onto the top of the injector (where the fuel feed line goes). The injector shop I go to is happy to loan theirs out for a couple of hours in return for the injector rebuilding/purchasing. Last time I had a stuck injector took two strokes with the slide hammer.
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Old 03-10-2012, 21:02   #27
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Re: Yanmar 3GM 30 Hard Starting

Guys I came across this on the Torresen Marine website,

NOTE: If your European version 3GM30/F series engine is starting hard it is due to a check valve failure between the fuel feed and injection pumps. The check valve can "dry out" and either allow air into the fuel system, or allow fuel system pressure to "bleed off" into the return system. It is recommended that you remove this late model fuel line and check valve, amd replace it with an earlier style fuel line, #128390-59010. Replace the long bolt that secured the check valve housing with a shorter, #26106-080142. Be sure to replace all the washers, 23414-120000 at the fitting also.

It will be necessary to remove the fuel line that ran from the check valve housing to a "Tee" fitting that connected this return line to the return coming from the injectors. Remove the return line, "Tee", and short hose from "Tee" to the output nipple on the fuel injector return line. Connect the fuel tank return line directly to the output nipple on the fuel injection return line.

It might be worth investigating.
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Old 03-10-2012, 21:22   #28
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Re: Yanmar 3GM 30 Hard Starting

On cold mornings (<50-degrees F) I use a bit of WD-40 sprayed in the air intake to start my 3gm30F engine. Works like a charm and easy on the engine too.
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Old 03-10-2012, 21:34   #29
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Re: Yanmar 3GM 30 Hard Starting

Quote:
Originally Posted by Cheechako View Post
I had that exact problem on the same engine. After 3 mechanics etc, we discovered that one ring land on one piston was cracked... just floating in there. Evidently this is not uncommon on the older GM series...
This could be the problem, if one of the injectors is defective and lets too much diesel into the cylinder, the temperature goes way up and will cause excessive wear. A taper forms in the cylinder wall and causes excess flex of the upper most piston ring resulting in blow by and ring wear in the piston grove. I sure hope I am wrong as the fix for this is expensive.
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Old 04-10-2012, 10:17   #30
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Re: Yanmar 3GM 30 Hard Starting

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Originally Posted by ScuzzMonkey View Post
So, since I'm in the same neck of the woods, would you be comfortable posting the name of the golden mechanic who figured it out, so I can avoid going through the first two myself?
Actually, this was in the carribean. a mechanic in St Thomas finally figured out after one in Antigua rebuilt the head to no avail!
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