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post #1 of 39 Old 07-17-2013 Thread Starter
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Yanmar hard starting question

Hi all, I have 3gm30 in my C&C which when cold or simply not run for awhile is difficult to start and requires quite a bit of throttle to get it going. It thens runs a bit rough (5-10 sec) until it seems to "clear out" and then runs good. When started it smokes quite a bit (black) but then stops smoking. Overall a good running motor except when starting up.

Thoughts??

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post #2 of 39 Old 07-19-2013
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Re: Yanmar hard starting question

3GM is probably much like 2GM. Because it has no glow plugs, mine was reluctant to start from cold until I learned the technique.

With sea water **** CLOSED, throttle CLOSED, crank it on compression for about 5 seconds. OPEN sea water ****, FULL throttle - and with one hand on the throttle to catch it before it over-revs - hit starter. As it fires and accelerates through 1000-1200 rpm, smoothly reduce throttle to a fast idle (about 1100 to 1200 RPM - any less and it will probably stall if it's really cold).

Maybe if the engine has been idle for a while you will want to initially turn it over (with the seacock CLOSED!) with the decompression lever actuated just to circulate the oil. But to get it running, it needs some heat in the cylinders, and the quickest way to get that without glow plugs is to crank it on compression for about 5 seconds before putting in fuel. Personally, I think that just cranking it gets the oil moving enough without the decompression thing being necessary. I only use the decompression lever after an oil change to make sure the filter is primed.

footnote: I see the English word for a valve, starting with 'c' having an 'o' and another 'c' before ending in 'k' is automatically censored to four **** Unbelievable prudery.......

Last edited by arvicola-amphibius; 07-19-2013 at 01:31 AM.
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post #3 of 39 Old 07-19-2013
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Re: Yanmar hard starting question

Same engine in my C&C 35/3!
Yanmar recommends a lot of throttle when starting - at least half and possibly more. Back smoke is unburned fuel. Its possible that the injectors are in need of servicing, but if it runs fine otherwise I would not worry about it.
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post #4 of 39 Old 07-19-2013
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Re: Yanmar hard starting question

My 3GM30F sometimes does that. I have assumed it gets a little air into the fuel system when it sits for some time. Haven't been able to prove that however. No leaks evident.
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post #5 of 39 Old 07-19-2013
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Re: Yanmar hard starting question

If you have followed the troubleshooting steps for the problem, and it is not low compression or injection timing, or one of the other mechanical issues try running the Power Service Diesel Kleen product through it. A lot of times you get some minor injector nozzle buildup that keeps the swirl pattern from being just right until the cylinders heat up a bit, the Power Service will help this a lot.

Just in case you do not have your service manual..

http://www.yanmarmarine.co.uk/pdfs/s...al/EPB5494.pdf

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post #6 of 39 Old 07-21-2013
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Re: Yanmar hard starting question

I have a 2QM15, also without glow plugs. Your starting characteristics seem similar to mine.

Here's my method:

1. Crank for about 5 seconds with throttle closed. This pre-heats the cylinders from compression, but without loading up unburned fuel (which will cause smoking and fuel on the water when it starts).

2. Advance the throttle to full open, still while cranking. As engine begins to catch, pull back on the throttle to avoid high revs. Settle into a moderate idle, and observe oil pressure rise and cooling water flow.

I keep the seacock open for this entire evolution (I don't like running the impeller dry), but be careful of excessive cranking with the seacock open, since you'll eventually fill the exhaust line and muffler with water and it will enter your engine.

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post #7 of 39 Old 07-21-2013
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Re: Yanmar hard starting question

If you had a tractor with a yanmar, you would use this LOL

GLOW PLUG (THERMO-START PLUG)

Pretty dangerous on a boat imho.

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post #8 of 39 Old 07-21-2013
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Re: Yanmar hard starting question

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Originally Posted by deniseO30 View Post
If you had a tractor with a yanmar, you would use this LOL

GLOW PLUG (THERMO-START PLUG)

Pretty dangerous on a boat imho.
There really is nothing at all wrong with having glow plugs on a boat, most diesels from other manufacturers do have them. Yanmar chose to leave them off on their older models for who knows what reason, however, the newer Yanmar engines have the glow plugs, and no compression release valves. Small diesels under 10 liters generally have them, except for the very small and the very old ones. All automotive diesels currently installed in cars for sale in the US that I know of have them, and I believe that is the way they come worldwide.

Even though you may think having fuel and heat come together in the same place sounds like a bad idea, it is the only way you get combustion, which is kind of important in the internal COMBUSTION engine. The trick is that the combustion stays internal, and the Yanmar glow plug does not risk external combustion any more than any other glow plug system would do.

This is a UNiversal/ Westerbeke pencil type glow plug. All Universal/Westerbeke engines use them, though the type and style vary. Unfortunately I have not seen a way to install glowplugs on the Yanmar Marine Diesels.



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post #9 of 39 Old 07-21-2013
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Re: Yanmar hard starting question

Building a diesel without glow plugs is cheaper than building it with them. And since recreational boaters are cheap and tend to not use their boats in cold weather...It sadly makes good sense to build cheap engines without glow plugs.

It also would make sense to check the options for the engine oil. Most old manuals will spec a single-viscosity oil because motor oils weren't very talented 30 years ago. These days? Odds are you can use a good synthetic, and those are available in multi-viscosity ranges like 0W40 or 0w30 which make cold starts real easy. Much kinder to the engine.
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post #10 of 39 Old 07-22-2013
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Re: Yanmar hard starting question

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Originally Posted by hellosailor View Post
Building a diesel without glow plugs is cheaper than building it with them. And since recreational boaters are cheap and tend to not use their boats in cold weather...It sadly makes good sense to build cheap engines without glow plugs.

It also would make sense to check the options for the engine oil. Most old manuals will spec a single-viscosity oil because motor oils weren't very talented 30 years ago. These days? Odds are you can use a good synthetic, and those are available in multi-viscosity ranges like 0W40 or 0w30 which make cold starts real easy. Much kinder to the engine.
Actually most marine diesels are not Yanmars, and everyone else uses glow plugs. Yanmar chose not to do so, and the cost at time of fabrication would have been miniscule, in fact Yanmar went to glow plugs after the GM series, the YM and JH series and I believe the QM series as well have glow plugs. It was a design flaw, probably due to an engineer not thinking about the fact that not all sailing is done in the tropics LOL.

The flaw is what it is, and the best way to deal with it is to treat the fuel, the tanks, and the entire system and make sure that the engine is well lubricated and maintains good compression. The Yanmar is very ticky about compression being high enough, so a slight loss in compression makes them a total pain in the arse to start when cold. Power Service additives will help this problem tremendously, and help more than you might imagine. Also the Lucas Oil additive which improves all temperature viscosity is worth using.

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