Yanmar 2qm15 starts hard

[Mike8221]

Yanmar 2QM15 starts hard
Engine turns over nicely and has spark, but acts like it may be getting too much fuel. Some black soot/oil coming from exhaust but only at startup. I use about 75-80 pct throttle when starting. I have also experimented with less throttle with no improved results. Last year i had injectors rebuilt. New fuel /air filters. This year i cleaned the ground wire connection which helped a lot. Is it possible i may still have a weak ground connection?
I hate to leave an oil slick evertime i startup!

 

[navigator97]

How old is the Starter Motor? It has brushes which do wear some over time, and the Magnetic Switch (Solenoid) which can get pitted contacts over time. This of course should not affect how much black smoke you are getting, unless you have to turn over the starter a lot before it fires up. The mixing elbow will "coke up" over time. If its been about 500 or 700 engine hours since it was replaced (or cleaned), that build up in the elbow will cause back pressure which will make the engine perform inefficiently and unburned fuel will come out as black smoke. How long since the mixing elbow was changed?

 

[Mike8221]

How old is the Starter Motor? It has brushes which do wear some over time, and the Magnetic Switch (Solenoid) which can get pitted contacts over time. This of course should not affect how much black smoke you are getting, unless you have to turn over the starter a lot before it fires up. The mixing elbow will "coke up" over time. If its been about 500 or 700 engine hours since it was replaced (or cleaned), that build up in the elbow will cause back pressure which will make the engine perform inefficiently and unburned fuel will come out as black smoke. How long since the mixing elbow was changed?

Never replaced. Once started, there is no smoke.
I forgot to add that i do need to give the motor extra boost by holding the starter button longer tha normal, as much as 10 seconds.

 

[kloudie1]

How many hours on the engine, Mike?? I am assuming fresh, clean diesel.. Hard starting producing an oil slick can be many things, some very expensive to correct. Make sure the fuel lines have been bled of air recently. Next, check the valve clearance to make sure the valves are closing completely; correct that and test before going any further. If the clearances are too tight, the compression pressure will be decreased and the engine will be hard to start. .. that one is really cheap and easy to fix.. The next thing to do is to have a diesel mechanic do a compression check to see if the rings are getting too worn, or the valve seats are leaking. When he does that, get the injectors rebuilt or replaced.. A dirty/fouled injector tip can cause a poor spray pattern that is hard to ignite.. The results of the compression test will tell ya if the engine should have the piston rings replaced or the valves re-seated. Get a good, trustworthy, real diesel mechanic to do this work unless you are comfortable doing a compression check and have the correct tools to do that and the injector work. Good Luck

 

[bria46]

Start with replacing the glow plugs. This info came from a Westerbeke mech. I did mine and the black diesel smoke was greatly reduced. Much cheaper than doing other service on the Yanmar

 

[kloudie1]

OK, that engine doesn't have spark nor does it have glow plugs.. Only newer Yanmars have glow plugs..
The other thing is that I am assuming, besides good clean fuel, is that the starter is spinning the engine at a "normal" speed.. sounds kinda like a car starting speed..

 

[healeyman]

Mike, ..1 you say that it 'will' eventually start and run. then I doubt that you have air in the line. but you might have a weak fuel pump 2..check the fuel pump by removing the fuel line at the secondary filter on the engine and turn it over... if a goodly amount of fuel is pumped then pump is ok. 3. Then a compression check would be in order.. (you mentioned 'has spark' this is a diesel right?) good luck...

 

[Stephen Trapani]

Had trouble starting mine until I got a bigger CCA battery to turn it over faster. Also, different throttle will work best for starting depending upon how much it has been sitting. When cold I "pump" it from 100% to 65% to find the starting sweet spot.

 

[Mike8221]

Kloudie, when the injectors were rebuilt last year the mechanic, also a sailor, did a compression check and fuel pump check and said both were ok. I like your suggestion about the brushes and solenoid and will look at those.

 

[Mike8221]

All of your suggestions are good and I appreciate them. I will be back onboard this coming Thursday and will post results.

 

[BobM]

2QM15 owner here

Check the connectors on the back of your alternator. I was having an intermittent starting problem I traced to a loose alternator wire. It likely vibrated its way loose.

Don't forget the compression release. I rigged a line to mine for cold starting. Release compression, hit the starter button for a few seconds than let go of the compression release. Big difference. I have have to use it in cold weather (sub 50F), but have never had a warm starting problem.

 

[BobM]

Another thought. How are you shutting her down? After running at low speeds through the mooring field to pick up my mooring I wait until I am all secure that rev up to 2800rpm in neutral for a minute before shutting her down. That burns out any deposits accumulated during the sustained period at low RPM.

There is also a known problem with the substandard wiring on these early Yanmars. It can be fixed by adding a relay closer to the engine and replacing the wires to and from the key with wires to and from the relay and larger wires to from the engine/battery. I should do this, but it hasn't been too much of a problem. The intermittent thing has been a bigger headache. Hopefully the loose alternator wire was it. Seems to happen only after the boat has sat a while.

 

[Mike8221]

I have tried shutting down as you suggest, but have never held the high rpm for more than about 5 seconds. I will try it this weekend
I will double check the connections on the back of the alternator. Thanks.

 

[bbowman294]

I had to install an additional solenoid on my Yanmar 3GM30F engine in my Island Packet 29. made all the difference in the world in starting. I got it from Napa. Also, check your exhaust elbow. Several years ago I couldn't get my engine to start. It turned over and did everything it was supposed to do except start. Called in the experts - they were stumped......until we hit upon the engine exhaust side of the elbow. I replaced it (it could have been cleaned) and the engine started right up.

Bill

 

[nutheastah]

Yanmar 2QM15 starts hard
Engine turns over nicely and has spark, but acts like it may be getting too much fuel. Some black soot/oil coming from exhaust but only at startup. I use about 75-80 pct throttle when starting. I have also experimented with less throttle with no improved results. Last year i had injectors rebuilt. New fuel /air filters. This year i cleaned the ground wire connection which helped a lot. Is it possible i may still have a weak ground connection?
I hate to leave an oil slick evertime i startup!

Diesels need to crank at at least 300 RPM to fire. so make sure you have good batteries and cables. Some sandpaper and baking soda and water and clean all connections. Throttle position at starting should not cause the black smoke as the throttle only allows the governor to go off idle it wont hurt to go to full throttle during starting and once it lights drop it back. the black smoke is probably caused because of long cranking time and the cylinders getting wet. make sure that the shut down cable or solonoid is fully going to the start position as this can cause insufficient fuel supply to the pump. Diesels need high compression to heat the air in the cylinder to fire(compress the air molicules). 3 immideate causes to look for are cranking speed, fuel supply and air intake restriction. I would suggest a full throttle run occasionally as it keeps soot and unburnt diesel from building up in both the intake and exhaust.Also allow a couple minutes of fast idle before shutdown.

 

[dentonflyer]

You talk about the ground wire connection. Dumb question but what does that do for the start?

 

[Peppercorn]

Same problem same engine, I found the air filter had been sucked into the intake! Never saw that coming. During my extensive research two things really stand out. First compression, or lack of, will create a multitude of problems with starting. Second the mixing elbow will cause the smoke / black carbon gunk and the hard to start issue.