Yanmar 2qm15 fuel problem - SailNet Community

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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance > Engines > Diesel
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Diesel This is a new forum dedicated to diesel engines and their applicable accessories.


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Old 04-05-2011
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Yanmar 2qm15 fuel problem

I have a 2qm15 which had gotten water in the tank several times before I figured out what was going on. I cleaned the tank, lines, replaced filters and it ran fine for awhile. Now it is difficult to start when cold, dumps raw fuel out the exhaust with black and white smoke, then mostly clears up, and will power up in or out of gear to almost full power. However, when I throttle back, then up again, it belches raw fuel, black and white smoke. I pulled the exhaust elbow and found the smaller line coming from the cylinder head into the elbow almost blocked. Cleaned it out and replaced the elbow, but still has raw fuel, black and white smoke out of the exhaust.

Received several suggestions from this forum that it might be injectors. I pulled them, sent to shop but the nozzles were fine. Noticed one nut on each retaining bracket was finger tight. I think they should be torqued to 12 lb. Could this be the problem, or any other suggestions? Shop guy didn't think it was the injector pump.
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Old 04-05-2011
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Providing your injectors performs as to specs when it comes to opening pressure, no 'drips' and spray pattern, I would do a compression test.
The pump clearly gives fuel needed and a bit more, engine does not burn it!
That pump can not start giving more than it is set to deliver, however it might give it later.
Suggestion:
1: Do an injection timing check.
2;Do a compression check on both cold and hot engine.
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Old 04-05-2011
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The line that was clogged, are you refering to the cooling water line that goes to the exhaust elbow?

Maybe you should check that the entire exhaust system after the elbow to the stern of the boat is clear and not clogged causing excessive back pressure on the engine exhaust.
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Old 04-06-2011
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Just replaced the injectors. Engine started right up with a little starting fluid, ran better than in a long time, but still dumping a lot of raw fuel through the exhaust, so could only run it momentarily. Is compression test and injection timing check something I can do?

I'll try checking the rest of the exhaust system, but seems to run too well for much back pressure.
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Old 04-06-2011
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Will it not start at all without starting fluid? Interesting that it ran better, but you really didn't change anything, right? The injectors were not rebuilt? There could be a lot of diesel in the muffler that is still puking out, but that should clear up fairly quickly.
Unless you have access to a diesel compression gauge and the correct fittings you won't be able to do a compression check yourself. Some shops prefer to do a bleed down test using compressed air and measuring how long the cylinders will hold a certain PSI.
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Old 04-06-2011
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Quote:
Originally Posted by pfirth View Post
Noticed one nut on each retaining bracket was finger tight. I think they should be torqued to 12 lb. Could this be the problem, or any other suggestions? .
Yes, loose mounting bolts would cause a compression leak.
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Old 04-07-2011
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Please let us know final out come. It would be interesting. If you have unburned fuel and injector spray patern is good, sounds like either worn piston seal or bad valve seal. A compression test ( or pressure drop test) should tell you if this is the problem. Sounds likely as when piston is compressing, leak by would allow unburned fuel into the exhaust. Could try adjusting valves- very basic procedure and instructions in the Yanmar operation manual.
Good luck.
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Old 04-08-2011
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One other observation....as I was bleeding the lines after replacing the injectors, noticed the front cylinder had considerably less volume coming out of the injector fitting than the rear cylinder. Could this cause improper or no atomization leading to a drip? If so, do I get the injector pump rebuilt?
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Old 04-08-2011
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Quote:
Originally Posted by pfirth View Post
One other observation....as I was bleeding the lines after replacing the injectors, noticed the front cylinder had considerably less volume coming out of the injector fitting than the rear cylinder. Could this cause improper or no atomization leading to a drip? If so, do I get the injector pump rebuilt?
Sounds logical if the injection fuel pipes were bothed loosened the same amount to bleed. Probably be worth having a shop test the pump the reinstal and check injection pump timing. On my Yanmar you need to shim the pump to set the timing.
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That "could" mean the pump is weaker on one cyl..

An easy test is to take the injectors out and put the fuel lines on them (off the engine) so you can see the spray pattern. Use 2? plastic/glass see through cups and have someone crank the engine so you can look at the patterns.

DO NOT put your hand in front of a firing injector or it will inject you with fuel and you will need a hospital!! Use see through plastic/glass cups to get the visual on a pattern

Patterns should be the same on both if the pump is good.
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