Another hard starting 3GM-30f hard starting issue

[boeing1]

agree with 500 hours would Not tear into the engine
I would check it on a warmer day or preheat the engine compartment and recheck how it starts.
i see Boston has had some cold weather...

[Compass790]

I'd do the valve head clearances anyway as it's 'sposed to be done every 300hrs on our yanmar. No way you should need a head rebuild at those hours. Dont be frightened to use a bit of throttle.

[Diesel Bill]

I agree with the more throttle at start up crowd. Don't tear any thing apart till you know it needs it. Also agree to check valve lash. Have a spare cover gasket on hand as the cork ones sometimes disintegrate on removal.

[Matsubob]

If the engine has only 500 hours on it, does that mean it was overhauled? And if so, how far? Sounds to me like a stuck valve or one of the decmpression levers is in the wrong position. If it were a cracked piston, the issue wouldn't "go away" after warmup.
It could be one of the tiny little parts in an injector being partially stuck until it is run for a while, or same for the injector pump. But if the engine runs smoothly after warmup, the slow starting problem should resolve itself.
The 3GM is a sweet little motor!

[maxingout]

I have 4500 hours on my 3GM-30F engines in my port and starboard hulls, and I adjusted the valves every 200 hours. So far so good.

I have been told that the engines are good for about 10,000 hours of hard running under load.

[lateral]

Originally Posted by 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.


Thoughts?

I have 3gm30F that does not like to start at < 15°.
<1000hrs over 20yrs. Sat for last 12yrs.
My work around, Pump the lift vigorously before, 1/2 throttle,
Keep starter turning until it catches on all,< 10 seconds.
The last thing I'm not keen on, but I've heard others doing it. Once warm
starts instantly.

[01kiwijohn]

Assuming you have a "soft start" feature on that big alternator?
I always give mine a little throttle at start up, then quickly cut it back to about 1200 or so.
I'd check the valve clearances, as it's easy to do and does have an effect on starting; I've noticed. The cover has a "o-Ring" and so do the bolts, so you may want to have new ones on hand before lifting that valve cover. clean the crankcase vent while you've got it off; That doesn't affect starting but it may as well be done.

[Wotname]

Originally Posted by Matsubob

If the engine has only 500 hours on it, does that mean it was overhauled? And if so, how far? Sounds to me like a stuck valve or one of the decmpression levers is in the wrong position. If it were a cracked piston, the issue wouldn't "go away" after warmup.
............!

Back in post #9, I mentioned a possibility of a cracked piston. At the time, I could not recall the details but I should have said "broken rings and piston ring lands" the #3 cylinder (only). This results in hard starting when cold but OK when running.

Much more info and detail in this thread http://www.cruisersforum.com/forums/...ar-107705.html

I do agree this is not likely to be this OP's problem but there is some bad history with 3GM30s during a certain period.

[sazarac]

Originally Posted by 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?

The manual for my 3gm30 says full throttle start. I had trouble starting cold without full throttle.

[roverhi]

The 2GM20 with 250 hours in my new to me Sabre 28 is hard to start in 50 degree weather. If throttle is at idle, will start but run very rough and die. Very hard to get it to fire again. Give it a lot of throttle and it starts right up. Any thing less on the throttle and it will start but run rough but eventually smoothing out.

[geoleo]

I had a Yanmar 3QM30f for 15 years. Its a great engine. Here is what to do.1. after it starts and warms up bleed the 3 cylinders at the fuel injector line one by one just crack the nut 1/4 turn for 5-8 seconds and then tighten. 2.Then get a quart of Marvels Mystery OIL . When you open it don't completely remove the foil seal . Punch a small holt about 1/16th . get engine running at about 1800 rpm and warm -not hot. Remove air filter. Pour a stream of the marvels into air filter soits getting sucked into engine- for about 30 seconds. This will burn a whitish smoke out exaust and make engine stumble a bit. There you have just cleaned the valves .

[phantomracer]

Just an update.. went to the boat today, about 70f out . Nice and warm out. The motor did start on the first flick of the key and ran flawless again. So perhaps it was just cold out and I didn't goose the engine when i started it cold.

I will be visiting the boat a few more times before it gets launched next week, will give it a few more test starts before getting too worried about it.

[Lepke]

Before you start doing valve and ring jobs...
If it's 50° during the day, how cold was it last night? How cold is the block?
Besides fuel, diesels need to compress air (that causes heat) to reach above fuel ignition temperature. So while rings and valves can be part of a problem, temperature is a big consideration. The colder temp you start at, the harder it is to reach ignition. Block heaters are ideal in cold temperatures. Engines well past their prime can start easily with enough heat. Glow plugs that heat incoming air can usually be installed in the intake systems of diesels that don't have them. Also oil pan heaters help. In a pinch, a hair dryer near the intake can help. If you don't know what your doing, ether, too liberally applied can cause rings to crack.

[Compass790]

Originally Posted by phantomracer

Just an update.. went to the boat today, about 70f out . Nice and warm out. The motor did start on the first flick of the key and ran flawless again. So perhaps it was just cold out and I didn't goose the engine when i started it cold.

I will be visiting the boat a few more times before it gets launched next week, will give it a few more test starts before getting too worried about it.

Good that it ran ok, I'd still do the valve head clearances if they havent been touched as its only a matter of time before you run into problems if they get too small but it's your call. Did you use some throttle this time?

[phantomracer]

Originally Posted by Compass790

Good that it ran ok, I'd still do the valve head clearances if they havent been touched as its only a matter of time before you run into problems if they get too small but it's your call. Did you use some throttle this time?

yes ill have a look at the valve clearance ... i did give it some throttle when starting