Subject: How do you hand start a Yanmar 3QMF
Here's my original question:
Date: Fri, 8 Jan 1999 10:52:29 -0800 (PST) Subject: lv-ab: How do you hand start a Yanmar 3QMFI have a hand-crank start option on my Yanmar diesel (came with the boat, installed 20 years ago when the first owner repowered). I've always thought that it would be a good back-up in case the starter gave up the ghost. The last time I was doing some maintenance and I had the cover off, I decided to give it a try. Suzy held down the decompression lever while I cranked madly, then she eased the lever back. Then I come to a dead stop. It is clear than I am not doing something right with this high compression diesel engine.
Has anyone else tried and succeeded in hand starting a diesel? How did you do it? The crank does have some other advantage for maintenance and repair, but I'm about ready to give it up as a starting method. I'm also afraid that my grunting and torquing might have knocked my engine slightly off alignment.
And here's what I've learned:
Although it is possible to start smaller engines (1, 2 cyl, <13HP, for example), or ones with a large flywheel, my 3 cyl, 27HP Yanmar (read the spec sheet!) is just too big for anyone not the size of a Redskins center forward. [successful examples were Yanmar 12HP, Volvo 13HP, Renault, Bukh] There was one dire warning to avoid kick back from the crank if you value your thumbs.
But! Several people suggested disconnecting the linkage between the three decompression levers (one for each cyl), hand crank one, then start #2 and #3. It will sound awful, but between the RPM governor and heartfelt prayer, it should work. I haven't tried it on my 3QM30, but others have said they've done it on their engines.
A few people suggested putting the throttle to "max." I talked to my local diesel guru and his reply was that diesels don't "like" too much fuel n the cylinder. First, any fuel that doesn't vaporize will leave liquid in the chamber, and you can't compress liquids. So only enough fuel to put a good fuel vapor mix into the chamber. Second, the injector pumps are designed to vaporize fuel at low RPMs, otherwise, the starting motor couldn't get things going either.
Easing the compression lever is the wrong thing to do. It must be switched off quickly.
It is very unlikely that I've changed the alignment of the engine with my hand cranking experiment -- given the forces that everyday use of the diesel exerts. One suggestion was that the decompression lever is "stuck" a little bit, thus changing the compression pressure. I've fiddled with it a bit and I'll see the next time I take her out.
So that's the gist of it. Thanks again everyone for all your help. I hope I never ever have to use this option, but if sh*t happens one day, it is nice to know that there's a backup -- also, perhaps that extra jolt of adrenaline will help. (Who was it that said the most effective bailing mechanism was a man with bucket afraid a drowning?)
Home Photo Gallery Tour Waypoints Wisdom Log Book Q&A Forum Search Contact Us
Copyright © 1999 Ken Mayer