Another hard starting 3GM-30f hard starting issue

[phantomracer]

Will be launching soon, so started up the motor on the hard, it is giving me a hard time!

Been super reliable all these years. Motor has about 500 or so hours (hour meter died, but its a reasonable gestimate)

Somewhat cool out - about 50F or so

Symptoms: upon cranking (new, fully charged battery), little or no throttle (never needed any), engine starts, a bit lumpy, for about 5 seconds. dies.

Cranking again, sounds like it wants to start, sputters, but doesn't catch. starter spins with gusto.

I am guessing it is getting fuel, as there are puffs of black smoke time to time coming out. eventually, after a few minutes of attempts (maybe 10 tries) it catches and runs like its brand new.

Bled the fuel lines - zero air comes out - just fuel.

Fuel is very clean - fuel from a high volume station, filtered when filling with mr funnel, electric lift pump has a filter - racor and engine filters are brand new.

Unsure if the engine is at the age that the injectors need to be rebuilt/replaced.... or the fuel injector pump is having gas pains... or something else (like fuel line mentioned on this post on this
THREAD

Not a hint of any smoke after running, like the engine is brand new, after it gets going. Maybe it was borderline cold for it to start??

Thoughts?

[hobopacket]

Maybe just having a hard time after the long lay up? How is it doing now? I mean after its run for the first time. Any better now that it's run some?

[SailsTeam]

Sounds like you need a valve job. Pull the cylinder head and take it to a machine shop for refurb. Take a look at your exhaust elbow too. If it gets really bad water can get into your cylinder head and cause this issue. You'll be running like new in no time.

[SailsTeam]

Originally Posted by hobopacket

Maybe just having a hard time after the long lay up? How is it doing now? I mean after its run for the first time. Any better now that it's run some?

Diesel engines in good condition start and run reliably even if you leave them sitting for 40 years. It's not a lawn mower.

[hugosalt]

err...before tearing motor down, try starting with 3/4 throttle, like Yanmar recommends for
cold starts. Then throttle back after she kicks in a few seconds.

[four winds]

Yep, more throttle per the manual. Though my old manual says "set engine speed lever to medium speed". I guess since it's not really a throttle.

With 3000 hours mine only starts at idle setting when warm after use. In cold weather half throttle and few more seconds cranking are needed.

Also with only 500 hours, do you know if the valves have ever been adjusted? Initial is at 50 hours and then every few hundred hours thereafter, or something like that. Didn't look it up. Your's may have been adjusted twice by now if up on maintenance.

[Hunter33]

My qm20 sat on the hard for two years and it started first time no problems it is 40yrs old now

[phantomracer]

Thanks, i will try starting with throttle. Something I have never done before though. Then again, haven't really read the manual Took a 3 day class at Mack Boring.. but never read the manual!

It always hesitated starting in the cold (30-40) but never 50+F

I have never adjusted the valves (had the motor since hour 20). I'll have a look at that if I have the time. I thought that inspecting the valves was at 1000 hours. but will have a look at it

mixing elbow is checked/cleaned every year. did that when i changed the oil in the fall.

Hopefully all it is that it wants more throttle at startup.

[Wotname]

I agree with most of the above

Difficult cold starting does suggest a decreasing compression and it might or might not be a problem yet.

Another possibility could be a cracked piston which was a problem with some 3GM30s - apparently there was dud batch that got pass Yanmar's Q control. Classic symptom was hard starting but ran well after that (I think). Other members (like SailorChic) will know more detail.

FWIW, my 2GM20 with 300 hours starts perfectly at 30 F with no throttle but I agree that cracking the throttle some more is a good idea when cold.

[SailsTeam]

Whatever you do don't use any starter fluid even if it says its ok for diesel engines.

[Jacko]

Hey guys n girls eazy on this chap you don't start pulling heads at 500hrs I had one of these babies ( 35 hp ) for 14 years and experienced all sorts of adventures during that time.
I might suggest get some use on the motor put it back in the water and run it on the dock in gear for an hour or so at 1500/2000 rpm . All sounds good with filters and fuel so the best thing for these fantastic motors is hard work they love it. I did 5k + hrs and the motor was like new run hard the whole time pushing a big boat, we seem to be getting a bit sooky about hours on motors we should ( and proven ) get many more hours than is the general perception. Biggest problem is lack of use and lack of putting the diesel motor under load.
I have up graded to a 75hp turbo Yanmar WOW My Boat is 20 ton so now I am living the dream Yaaaaar hoooooo

[sailah]

In the unlikely event you need engine machine work in the Boston area I had great help from Reids Automotive in Whitman and boston injection in Charlestown. Both were highly knowledgeable in their fields and delivered quickly without the marine markup.

[phantomracer]

will be visiting the boat at least 2x before launch day. hopefully it will magically work better, as the weather is supposed to be warmer (70f) and ill try to goose the engine a bit when starting as well

The only change since last year, I can't imagine it makes a difference, is I added the 'alt belt' serpentine belt kit from balmar, as the 100 amp alternator was eating v-belts for dinner. Perhaps now that the belt isn't slipping, the additional load may be part of the hard starting problem? Other than that, everything is Yanmar brand, down to the oil and coolant!

[Hunter33]

The biggest problem in starting is you must have clean fuel and no air in the fuel system

[phantomracer]

Originally Posted by Hunter33

The biggest problem in starting is you must have clean fuel and no air in the fuel system

yup. exactly. fuel tank is emptied and washed down every 3-4 years, fuel is filtered 4x before getting to the injectors. Fuel is purchased from a high volume station. don't know how to get cleaner fuel than that. fuel lines bled after changing the filters last year, bled a couple times this spring (not a single burp of air came out of the bleeder). Have an electric lift pump to ensure good fuel delivery