Yanmar 3GMF starting hard

[Charlie98117]

I have a 3GMF that is beginning to have some issues when starting when it is cold. Previously I would give it full throttle when cold and it would take off fairly quickly. Lately it has been getting harder to get all 3 cylinders going, and when it finally does, it blows out a cloud of black smoke. After an initial run there are no problems starting - I run it for a few minutes to get out of the marina then go sailing for several hours and it will start in a couple revolutions with even no throttle.

Any ideas on what could be causing the difficulty starting when cold?

 

[walmsleyc]

My 30 year old 3GM30F always requires close to full throttle for starting in spring and in fall (when it's cold/cooler) and it take a 3-5 seconds maybe. During the summer, I still give it 3/4 throttle, but is starts very quickly. It usually kicks out a puff of black smoke upon starting too.

Chris

 

[seadaddler]

When did you check or change Mixing Elbo and mine was hard starting until I
changed out the mixing elbo.
Nick

 

[Charlie98117]

I had a new elbow installed in the fall of 2014 so hopefully that is still clear.

 

[druid]

Yanmar recommends full-throttle starting for the 2GM/3GMs. Remember they have no form of pre-heating (like a glowplug) so yes, in cold weather it will take a bit before the cyls get hot enough. If one or two cyls are much harder to get going, I'd suspect "the usual suspects": clogged injectors or low compression. I'd say probably NOT clogged exhaust because that would affect all cyls. Pull the injectors and have them checked/cleaned/rebuilt. If the injectors are fine you'll have to look at more serious stuff, like valves not seating or just plain wear on the rings/cyls.

druid

 

[Charlie98117]

Thanks for the reply Driud. I was thinking it could be injectors but unsure why it would only be a problem when cold since it starts right up after cooling down during 4 or 5 hours of sailing. Once running it seems to have full power, 7+ knots at 3200 rpm. Low compression would translate to low power, correct? I'm a decent mechanic but new to diesels so still learning what makes them tick.

I sail all year round and didn't have this much trouble getting it started even last winter when it was 35 degrees out. Something has definitely changed or become clogged.

 

[Allan12210]

Mine started doing that. Turns out there was an air leak and the fuel would drain down somewhere after sitting awhile (1 week +). I'd have to crank for a long time before it would fire off. The fix was to replace all the copper crush washers on the primary filter and where that line goes into the injector pump. It solved the problem and I always start in the idle position. A couple of weeks ago we went to the boat and I had to start it after 6 months of sitting (that's another story). It probably had to crank about 1/8 revolution and it was running. I couldn't believe it. So, check for air egress too.

 

[NYSail]

Before you pull he injectors, have you cleaned them? Try a can of sea foam.... Auto parts stores sells the stuff. Will clean the injectors..... I noticed significant improvement.

 

[Charlie98117]

That's why I love this place, great suggestions. Thanks, gives me someplace logical to start.

 

[mz4wheeler]

Any ideas on what could be causing the difficulty starting when cold?

Crazy as it sounds, I ALWAYS start at minimum throttle. Just a light click and it's gong. Starts (almost) every time. Starting with a puff of black smoke indicates too much fuel.

 

[Sailm8]

Same problem, new injectors fixed it.

 

[Benny17441]

Diesel fuel is ignited by compression. On startup compression is built up gradually by a number of revolutions. These revolutions need to happen relatively quickly as not to loose too much of the compression already built up by previous revolutions. The causes for slow cranking can be low batteries, poor connections, faltering starter, cold thick oil, restriction in the intake or exhaust. If the engine is cranking fast enough but compression is not building up then there is a poor seal in the valves or piston rings. Contrary to fast cranking a thick oil can enhance piston ring seal and thus compression. For a well worn engine I would recommend 15W40 with an additive. As far as the black smoke it just points to incomplete combustion of the excess fuel that had been accumulating in the cylinder. Another possibility is poor fuel condition. Maybe a tankful of diesel with high water content.

 

[Charlie98117]

Thought I would add an epilogue to this thread. It kept getting worse until one day it just wouldn't go. Decided to bleed it starting from the bottom. The second bleed point is at the high pressure pump and when I got there I noticed a bit of fuel on top of the cover. I bled that location with my wife cranking and it started up as soon as I tightened the screw. Apparently the bleed screw was leaking just enough to allow some air to enter when it sat for a few days. It now starts within 5 seconds with no throttle.

 

[MitchM]

yan mar recommends you install new copper crush washers when you change the primary filter. the old washer takes a 'set' and when you reinstall it, it may not seal well. then you have a brand new fuel filter but a tiny air leak so s trying is very hard. you c an rx the copper crush washer by heating it red hot then flattening it out if you are desperate and have the inclination. (that always seems like a lot of work to save 50 cents..) look up full instructions on how to do that and make sure its flat if thats your choice.. i just carry some extra copper crush washers...