Full throttle needed to start Yanmar 2GM20F - Page 2 - SailNet Community
Reply
 
LinkBack Thread Tools
post #11 of 25 Old 12-18-2012 Thread Starter
Member
 
Join Date: Dec 2012
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Full throttle needed to start Yanmar 2GM20F

Quote:
Originally Posted by L124C View Post
I have the same motor as the OP. I always do a cold start at 3/4 throttle, throttling back to idle immediately after start, as directed in the manual. It's over 20 years old, does not have glow plugs, and has never had a starting problem (in the moderate SF Bay Area climate). Kicks on the first crank every time! Once warm, it starts immediately from idle position.
Sounds like a good Yanmar mechanic is in order for the OP. If he is in the Bay Area, List Marine will sort it out in short order. I'll bet they will also tell him to cruise at 3000 RPM when it is running properly. Makes for a happy 2GM20!
Opposite end of the country. I am in NY Long Island Peconic Bays area, pretty much the same climate. My engine at this point stalls after start if I pill back to idle immediately, I have to keep it in the 2000 to 2500 revs until it smoothes out. And, when warm when its running it sounds like there is a man with a hammer in the engine (mechanics called this fuel knock).
73Morgan is offline  
Sponsored Links
Advertisement
 
post #12 of 25 Old 12-18-2012 Thread Starter
Member
 
Join Date: Dec 2012
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Full throttle needed to start Yanmar 2GM20F

Quote:
Originally Posted by Faster View Post
I think OB and Minne are on the right track.. while 350 compression may be on the low side I don't think it's low enough to make starting problematic with good fuel delivery. And that means timing and proper atomization.

If you're cranking for excessive time periods try to remember to leave your RW intake closed until the engine catches. Flooding the exhaust system with RWC is never a good thing.

Having to use wide open throttle during starting seems to be SOP for some of these older Yanmars..
Ok, I am listening, does this apply to fresh water culled engines?
73Morgan is offline  
post #13 of 25 Old 12-18-2012 Thread Starter
Member
 
Join Date: Dec 2012
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Full throttle needed to start Yanmar 2GM20F

I looked into compression, and I see that the manual says the Compression Ratio should be at 23, multiplied by atmospheric pressure 14.7, this equals 338 PSI. Surprisingly 350 is above that. The Mechanic did say he took the compression with a warm engine. He also said that the rings might be stuck/frozen, this might make a difference with a cold start. It looks like he might be on the right track.
73Morgan is offline  
 
post #14 of 25 Old 12-18-2012
Senior Member
 
Faster's Avatar
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 19,488
Thanks: 160
Thanked 587 Times in 558 Posts
Rep Power: 17
     
Re: Full throttle needed to start Yanmar 2GM20F

Quote:
Originally Posted by 73Morgan View Post
Ok, I am listening, does this apply to fresh water cooled engines?
Yes.. in either case the RW is pumped through the engine (RWC) or a heat exchanger(FWC) and then is injected into the exhaust system to keep the noise level down and to cool the exhaust run out to the transom.

The water is driven out of the exhaust system by the running engine's exhuast gases. If the engine never catches, the rotating RWpump will fill the muffler, eventually possibly backing up into the exhaust manifold where it will find an open exhaust valve and run back into that cylinder. This can cause 'hydrolocking', where the engine won't turn because it can't compress the liquid pocket in the cylinder.

I'm still leaning toward a faulty injector, certainly it's the top candidate for the 'hammer' sound while running.

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Faster is offline  
post #15 of 25 Old 12-20-2012
Senior Member
 
aa3jy's Avatar
 
Join Date: Jul 2006
Posts: 2,433
Thanks: 3
Thanked 109 Times in 101 Posts
Rep Power: 14
 
Re: Full throttle needed to start Yanmar 2GM20F

Cold start procedures for a 3GM30F(an indirect injection diesel) is similar..full throttle as described in the workshop manual which retards timing. Decrease throttle after diesel starts.

DO NOT use any starting type of sprays/fluids as this procedure may result in bent con rods. I personally know what bent rods look like...
aa3jy is offline  
post #16 of 25 Old 12-20-2012 Thread Starter
Member
 
Join Date: Dec 2012
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Full throttle needed to start Yanmar 2GM20F

Quote:
Originally Posted by Faster View Post
Yes.. in either case the RW is pumped through the engine (RWC) or a heat exchanger(FWC) and then is injected into the exhaust system to keep the noise level down and to cool the exhaust run out to the transom.

The water is driven out of the exhaust system by the running engine's exhuast gases. If the engine never catches, the rotating RWpump will fill the muffler, eventually possibly backing up into the exhaust manifold where it will find an open exhaust valve and run back into that cylinder. This can cause 'hydrolocking', where the engine won't turn because it can't compress the liquid pocket in the cylinder.

I'm still leaning toward a faulty injector, certainly it's the top candidate for the 'hammer' sound while running.
You just gave an excellent reason why I need to fix the starting issue. Water in the head at the valves and hydrolocking can result in some costly damage, aside from getting stuck somewhere and losing a good part of the season. Thanks, for the input.

I agree about the injectors. The way I understand it the injectors are the only thing that could be allowing too much fuel to get in the engine and cause fuel knock. If the Injection pup was failing that would result in not enough fuel. Are my assumptions right?
73Morgan is offline  
post #17 of 25 Old 12-20-2012
Senior Member
 
Faster's Avatar
 
Join Date: Sep 2005
Location: New Westminster, BC
Posts: 19,488
Thanks: 160
Thanked 587 Times in 558 Posts
Rep Power: 17
     
Re: Full throttle needed to start Yanmar 2GM20F

Quote:
Originally Posted by 73Morgan View Post

I agree about the injectors. The way I understand it the injectors are the only thing that could be allowing too much fuel to get in the engine and cause fuel knock. If the Injection pup was failing that would result in not enough fuel. Are my assumptions right?
That's been my experience.

On our last rebuild I ordered a full set of 'reconditioned' injectors. During the break-in period we got some fuel knock that scared the H out of me because it sounded like metal-to-metal contact.. gladly discovered eventually that one of the 'new' injectors was breaking over at under 500 psi = wet fuel = serious knock. Replaced injector and off to the races.

Ron

1984 Fast/Nicholson 345 "FastForward"

".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Faster is offline  
post #18 of 25 Old 12-20-2012 Thread Starter
Member
 
Join Date: Dec 2012
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Full throttle needed to start Yanmar 2GM20F

Quote:
Originally Posted by Faster View Post
That's been my experience.

On our last rebuild I ordered a full set of 'reconditioned' injectors. During the break-in period we got some fuel knock that scared the H out of me because it sounded like metal-to-metal contact.. gladly discovered eventually that one of the 'new' injectors was breaking over at under 500 psi = wet fuel = serious knock. Replaced injector and off to the races.
That is exactly what my knock sounds like right now.
You and a number of other people are saying the same thing about rebuilt injectors. Surprising that anyone even bothers with them.
73Morgan is offline  
post #19 of 25 Old 12-20-2012 Thread Starter
Member
 
Join Date: Dec 2012
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Full throttle needed to start Yanmar 2GM20F

Quote:
Originally Posted by aa3jy View Post
Cold start procedures for a 3GM30F(an indirect injection diesel) is similar..full throttle as described in the workshop manual which retards timing. Decrease throttle after diesel starts.

DO NOT use any starting type of sprays/fluids as this procedure may result in bent con rods. I personally know what bent rods look like...
If your engine was built after 1997 that might explain the difference. My manual covers the 1, 2 & 3GM models.
Normal start positing is at medium speed.
The exception is starting in cold weather the throttle should be in high speed with the decompression handle in the decompression position, start cranking and push the lever to the compression position, after it starts pull back to medium speed. There seems to be a conflict because there is a "caution" which states to pull back to idle immediately when the engine is started at high speed. We all know you should not rev a cold engine any more than necessary . The injection timing being delayed at high speed is also there.

I would actually be happy if the engine started right away on a 80 degree day, and came right back to idle without stalling.

Last edited by 73Morgan; 12-20-2012 at 05:03 PM.
73Morgan is offline  
post #20 of 25 Old 12-20-2012 Thread Starter
Member
 
Join Date: Dec 2012
Posts: 45
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
 
Re: Full throttle needed to start Yanmar 2GM20F

Ran some tests, cranking and playing with the decompression lever with a cold engine does not feel like it changes anything, it only feels like the compression builds up after the engine warms up. This just might be explaining the hard start problem.
73Morgan is offline  
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Yanmar 2gm20f RPM RobGallagher Diesel 2 06-30-2012 03:24 PM
Yanmar 2GM20F Suave Gear & Maintenance 2 05-16-2011 10:33 AM
Yanmar 2GM20F Work... krozet Diesel 15 04-28-2010 11:41 PM
Yanmar 2GM20F Petar Gear & Maintenance 13 10-02-2009 06:49 PM
Oh... the noise, running full throttle deniseO30 Diesel 2 06-29-2009 11:19 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome