View Full Version : Yanmar 3GM30F wont start

Marc Groves
03-23-2004, 05:04 PM
" Can anyone shed light on this please.
I have a 3GM30F which was extremely difficult to start. After having the head overhauled (incl 3 new exhaust valves), the head bolts tightened to the correct torque and the valve clearances set, the injectors checked, the outlet mixer cleaned, a full service done with new filters and new copper washers on ALL connections, the engine will not even attempt to start. "

03-23-2004, 07:53 PM
" Hi Marc! Been working on diesels all my live !
What makes them run , are the essentials!
That is Compression and fuel.If either one is missing ,they won,t go . "

03-23-2004, 09:32 PM

Marc Groves
03-24-2004, 10:40 AM
" Hi Holzralf & Marv, like you have been around diesels a long time, but only recently started on marine diesels.
Regarding my problem, I believe I have sufficeint compression, there is no blow back coming up the oil dipstick pipe, there is loads of fuel being 'spitted' from the pipes connecting to the injectors, the fuel limiter on the front of the engine casing has been asjusted in accordance with the manual, but alas, all to no avail. Any other ideas? "

Hunter User
03-27-2004, 10:17 PM
" My Yanmar 3GM30F is a bear to start as well. Two or three minutes of cranking are not unusual. People say that you should never crank for more than 30sec without draining the water lift muffler, but if I followed this advice I'd be doing that (however you do it) every time I start the engine. I think I need to add glow plugs to the engine -- there don't seem to be any. "

03-28-2004, 03:21 PM
" Hi Hunter User, yes, befoer all this happened the engine would need about 5x30 sec cranks. It would sound like that eventually 1 cylinder would fire then another then the 3rd, but the revs would have to be kept high or she would die out. I agree about the heater plugs since I cant keep starting the engine with a blow lamp!. My latest try is that I have removed the Inj pump and will send it away for testing - I dont expect they will find anything. "

03-28-2004, 04:56 PM
" A temporary remedy is to crank for a short while then wait a minute or two. Some fuel will then be able to settle in the cylinder giving the rings a better seal, increasing compression. Another aid in a pinch is to hold a rag soaked in WD-40 over the intake while you crank. The WD-40 is more volitile than Diesel fuel and might kick it off.
Eddie "

Joe Landrum
04-21-2004, 10:03 PM
Try this: it works on my 2GM20
Crank for 15 sec +- with compression release open (no compression) and throttle wide open. This soaks the interior of the cylinders with fuel.
Close compression release.
Start engine with throttle 1/2 open.

Howie Soule
05-07-2004, 11:07 AM
" Something is definately wrong. I have two boats each with the 3GM30F (one is chartered) and each starts within 3-5 seconds...very reliably. Occasionally, one may stall out but immediately restarts. I wonder if there is a fuel check valve somewhere or the pump that's leaking. In theory, after you shut the engine down, there should still be pressure. "

12-03-2005, 01:04 AM
"Was there ever water injested into this engines cylinders? If so, then one or more of the conrods have hydrauliced and become shorter. When you had the head off, did you see any water marks. That will cause hard/ no start. Usually hits the exhaust elbow side first as that is the end closer to the mixing exhaust elbow, and lowest in the boat. Compression should be around 380 to 410. Yanmar say about 460 but I have never seen it happen. Adjust valves to .008 How did the bores look? Could you still see cross hatch from the ball hone? Good luck. Let me know what u found?"

ken abrams
02-07-2006, 10:12 PM
First and foremost any Yanmar should start to fire in3-4 revolutions except in extreme cold. You most likely have LOW COMPRESSION. Svc limit on this engine is 396psi

poker casino695
03-06-2006, 06:16 PM
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01-04-2007, 04:54 AM
"Yanmars GM series are VEEEEERRRRYYYYY sensitive to their compressions. After repair and check of several engines, I marked up that piston rings are well used allready efter a few houndred hours... ( some allready at 400 hours... ). The cilinders themselves are quite resistant, a simple honing and new piston rings do the job in most cases!

Burned valves are more rare. A diesel engine flame is not THAT hot that you can easily burn exhaust valves. Check you have enough valve clearance ( better a little too much than too less... )

Let check and adjust your injectors frequently ( each 100 hours ). Adjusting is NOT expensive, and that will help a good start, less fuel consumption, less smoke, less noise AND a longer engine life!!!"

01-04-2007, 08:02 AM
"Just spray WD-40 directly into the intake as you are turning it over. Never mind the rag. WD-40 needs to be atomized, as does diesel fuel in order to burn. The rag will not let enough vapors off to start a candle never mind an engine. WD40 will not hurt the engine like starting fluid will. If your compression and timing is good it will start with WD-40 regardless of bad injectors, fuel pump, or glow plugs. If it stops when the WD-40 is stopped then your fuel system is at fault. This could be injectors, injector pump, fuel pump or bad fuel lines or bad fuel. If it does not start with WD-40 Then you have other problems. I am a professional with over 30 year’s in the business. Cranking any engine for extended periods of time is wrong. If any engine is not starting properly, then something is wrong. Cranking it until it eventually starts and then saying that Yanmars are like that is a load of crap. You have to systematically go through the systems to discover the problem. Good luck"

ted edwards
03-27-2007, 02:45 PM
"Looking for a used head for a 2GM20 Yanmar, can anyone help or point me in the direction of one?
Thanks for the help!

03-27-2007, 06:49 PM
"Ted, go to top of yanmar section and hit "start new discussion" maybe someone will see Your post. there is also a free classifieds at top of page. I have used it a couple of times, with good results. good luck."

05-16-2007, 07:48 PM
"How you doing friends my name is Darron and i ran into a problem with my deasil engine we tried to bleed the injecters,no deasil came out of the injector pump. Can it be clogged with dirt,or is it broken. Can it be tested,if so, how."

Elaine Leonard
06-08-2007, 10:49 AM
Own a 35.5 Hunter with a 3GM30F Yanmar. Just had the injectors rebuilt - engine runs nicely but now the engine dies out at anything below 1300 rpm's. Used to idle at about 1000 - 1100 rpms. Any idea why this would suddenly occur and secondly will I harm transmission shifting gears at 1300 rpm's? Many thanks.

06-09-2007, 09:37 AM
Yes ---you will harm trany shifting at 1300 RPM . Also 1000 at idle is to hi . Should idle 600 in gear.
Would sugest you get the timing checked.
best luck

06-09-2007, 01:43 PM
"check your compression, timing. if they are good, look at injection limiter. any smoke, or other symptoms? also, start a new string. this one is getting very long, and has nothing to do with original question."

Marty The 1
06-27-2007, 08:06 PM
"I have the same engine with 380 hours (7 yr old) this year it started to build pressure in the valve cover and leak oil around the valve cover gasket. When I remove the vapour return hose to the intake manifold, I get a white smoke at idle.

I checked the valves and some were too thight borught them all to 0.008 as per spec. the engine is not hard to start but needs the throttle lever at 25% to do it. THen after 1 minute I can bring it back to idle at 775 rpm. no unsual smoke at exhaust, I can bring it to 3000 rpm and it will deliver good power almost no oil cuinsumption just small leaks. I think may be a burnt valve?

Any other ideas?"

Daniel Daoust
11-08-2007, 09:18 AM
"I own a Yanmar 3GM 700 hours. Oil and filter changed every 100 hours. For the first time at end of season while running at 2000RPM the engine suddenly went down to 1200 rpm, increasing the fuel throttle would not do anything except having it to lower even more (sensing it would die).

I then proceeded at decreasing the fuel input (throttle) for a while ( 5 minutes) then when i throttled it back up and it ran fine again.

This scenario happened a couple of times so far.

Any Idea?


Maji Tembo
11-15-2007, 08:33 AM
I would not be surprised if you mixing elbow is clogged. I had the same problem and found that I had only a hole the size of a pencil remaining for the exhaust! My engine has less than 500 hrs. Easy to check.
s/v Maji Tembo"

2xs Sailing Charter
02-13-2008, 08:23 AM
off to check our mixing elbow just incase


http://www.sail2xs.co.uk ("")"

06-14-2008, 07:44 AM
Hard starting is often caused by insufficient fuel due to an air leak between the engine-mounted fuel pump and the fuel tank.

georgia boater
06-25-2008, 01:33 AM
I have a 2QM 20 Yanmar that is very hard to start.
My current mechanic is telling me it needs new injectors and another I consulted stated the compression is probaably low and I need a new/replaacement engine. Would like to avoid the engine route if at all possible. Noticed much air when I bled secondary filter (very recently replaced)...still would not start.

03-03-2009, 09:24 AM
"Last year I bought a second hand sailing yacht but there is no user manual for Yanmar 3GM30F engine.
I appreciate if anyone send it to my following e-mail adress. [email protected] ("")
Thanks for interesting"

04-11-2009, 11:07 AM
"Manual cost about $100 but well worth the cost. Any Yanmar dealer will have one in stock or will order it for you.

As far as the "hard to start" problem. In older boats that had a gasoline engine then upgraded to a diesel engine like the Yanmar, the batteries, i.e, 550 CCA (Cold Cranking Amps) to 1120 CCA, need to be upgraded as well because of the higher compression in diesel engines."

05-24-2009, 01:42 AM
"I, too have a 3GM30F which was a pig to start. (Especially when the temps were down) In the w/shop manual, Chap 13, they say for a cold start, open throttle fully, this retards the fuel pump timing for an easy start, then hit the Start button. I do use an old, one cylider Volvo trick tho, first pull out the Stop cable, and then push back in. Then open throttle fully, in neutral, then crank until she fires, five or six seconds. Keep the button in until she starts running and then reduce the throttle as the engine speeds up. Works every time! A cloud of smoke from the Rich start, but, who cares, the things running! Success!"

01-22-2010, 01:40 AM
"Some info for those that have hard starting 3GM30F YANMAR'S. I have one in my Hunter 340. A recent starting problem was caused by the "water cooled exhaust manifold / goose neck" being blocked, full of carbon build up to the point of almost no way for the exhaust gas to escape, thus choking the engine.
Remove and clean throughly, ie, chip out all the hard carbon buildup so there is the maximum possible diameter for the exhaust gas to escape.
Mine is still a bit hard to start from cold, needs half throttle, however always starts, very reliable with instant start when warm. Our temps here in Western Australia vary from approx 8c to 38c
Good luck."

03-23-2016, 03:47 PM
Could use of starting spray cause any damage?
I have a 3GM30 Yanmar in a 1998 sailboat which I purchased two years ago. The previous owner acknowledged it had been rebuilt and wasn't always starting quickly. It is getting harder and harder to start sometimes requiring repeated cranking. I have had valves adjusted, compression checked, injectors replaced, fuel filters replaced, and of course fuel line bled. When it does start it runs fine. I have, at the suggestion of a slip neighbor, tried a very small puff of starting fluid, sold in spray can which says ok for diesel and gas engines. It doesn't require much and just a short puff in the air cleaner intake does the trick, and it immediately starts the engine every time on first crank.