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Go Back   SailNet Community > On Board > 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 04-17-2010
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Yanmar 2GM20F Work...

Hey All;

This will be an ongoing thread as I continue to do work on my engine.

So today I get down to my boat and the first order of business is to get the engine running. I have serious doubts that it will run and if it is a write off I will have to cancel my planned sail back to Canada and have the boat trailer back to Toronto. I have budgeted my refit and have set aside plenty of money for work on the engine if needed but I am mechanically inclined so I want to see what I can do first. Maybe it will be straight forward and everything will be OK... I grab my Selco Yanmar Inboard manual and start at the beginning of the Maintenance & Tune Up section.

Engine Oil - Pull the dip stick and check, the oil level is a little high which seems OK as the engine hasn't been turned on in some time so all the oil has drained to the pan. Oil is black but manual says that is ok, the smell will give me more of an indication so I smell it. Smells like oil, no burned smell that I can detect.

Transmission Oil - Check the level, it is barely touching the dip stick... Seems to be in good shape, just not enough of it.

Coolant level - all looks good to me...

At this point the manual wants me to start pulling pieces off the engine to check them, no problem but I wonder to myself... would the engine even turn over? Well I grab the key, flip the battery selector to both, climb into the cockpit put the key in and turn it. I get the warning alarm and with my breath held I press the start button...

Chug, chug, chug, chug... It is trying to start... Chug, chug, chug, BANG!!!! It STARTS!!! It's actually running... wait a minute, its starting to run faster, the RPMs are getting quicker... I pull the engine stop and it sputters but doesn't stop, pull it a second time and another sputter but no stopping and the RPM's are still picking up. By this time only 5 or 6 seconds had gone by but it felt like hours as I tried to race through my mind how to stop it since I had not hooked up any water to the cooling system, holy fudge tarts the engine was going to BLOW UP!!! That's when I realized I had not checked the throttle, once I dropped it the RPM's slowed and pulling the engine stop successfully killed the engine.

WOW!!! I have a working diesel engine, well it worked for about 10 seconds before I stopped it! Once started there was no sputtering or hesitation either, it just ran.

So onto the checklist:

Air Filter & Crank Case Breather:

Things get weird at this point... I remove the silencer to inspect the foam element and screen. There is no foam element and the screen is covered in residue. The inside of the silencer has the same residue and some build up.

Screen:


Silencer:



The manual mentioned nothing about potential buildup, at first I thought it was rust and that the engine had water in it but it's more like burned oil... Any guess as to what this build up is? I am going to clean it and put it back on. Why would the PO not have a foam element?!?! Any number of nasty things could have been pulled into the engine...

As for the Crankcase breather, it has a couple drops of oil on the shelter plate but other than that it is clean.

I'll keep updating as I go along.
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Old 04-17-2010
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I think the buildup is just carbon but whats the safe way to remove it?

On with the inspection:

Fuel filter : looks great, and I learned how to bleed the system when I put it all back together. BUT..

Buildup in the filter cover, I have scrubbed at it with a shop rag but it is stubborn... How do you get this gunk out safely?



Belts : are in good shape.



Next is the raw & fresh water cooling systems, but I am going for lunch first...
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1971 Contest 33 Hull Number 24

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Old 04-17-2010
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Quote:
Originally Posted by krozet View Post
....but it's more like burned oil... Any guess as to what this build up is? I am going to clean it and put it back on. Why would the PO not have a foam element?!?! Any number of nasty things could have been pulled into the engine...

As for the Crankcase breather, it has a couple drops of oil on the shelter plate but other than that it is clean.
.
The build up is likely rubber dust from belts oil soaked from engine fumes and baked on from residual engine heat. That's my guess.

The PO likely had a "professional" look at or work on his engine. They often remove elements rather than clean them. It helps the engine breath but as you point out filtered air is better than non-filtered air even though it isn't much of a filter. Silencer is the correct term for that bit of plastic.

I would expect new modern engines to have air filters but maybe not on the small ones. Filtering the air was one of the biggest steps in extending engine life.
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Old 04-17-2010
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Quote:
Originally Posted by krozet View Post
By this time only 5 or 6 seconds had gone by but it felt like hours as I tried to race through my mind how to stop it since I had not hooked up any water to the cooling system, holy fudge tarts the engine was going to BLOW UP!!! That's when I realized I had not checked the throttle, once I dropped it the RPM's slowed and pulling the engine stop successfully killed the engine.
You obviously did the right thing to stop the engine. Just for future reference however their are conditions in which a diesel engine can run away with itself.

The most common solution in this case is to block the airflow. Paranoid folks have the air filter off and something that will plug the air intake but not get sucked into it available when starting a suspect engine.



The following quote is from wikipedia

Unlike a gasoline engine, which has a butterfly valve controlled by the throttle mechanism to control engine speed, a diesel engine's speed is controlled by varying the supply of fuel.
In many vehicles, a crankcase breather pipe feeds into the air intake to vent the crankcase; on a highly worn engine, gases can blow past the sides of the pistons and into the crankcase, then carry oil mist from the crankcase into the air intake via the breather. A diesel engine will run on this oil mist, since engine oil has the same energy content as diesel fuel, and so the engine revolutions increase as this extra "fuel" is taken in. As a result of increased revolutions, more oil mist is forced out of the crankcase and into the engine, and a vicious cycle is created. The engine reaches a point where it is generating enough oil mist from its own crankcase oil that shutting off the fuel supply will not stop it and it will run faster and faster until it is destroyed.
The unwanted oil can also come from failure of the oil seals in a turbocharged diesel engine, from overfilling the crankcase with oil, or certain other mechanical problems such as a broken internal fuel pipe. In vehicles or installations that use both diesel engines and bottled gas, a gas leak into the engine room could also provide fuel for a runaway, via the engine air intake[2].
The only way to stop a runaway diesel engine is to block off the air intake, either physically using a cover or plug, or alternatively by directing a CO2 fire extinguisher into the air intake to smother the engine.[3] Engines fitted with a decompressor can also be stopped by operating the decompressor, and in a vehicle with a manual transmission it is possible to stop the engine by engaging a high gear (ie 4th, 5th, 6th etc), with foot brake & parking brake fully applied, and letting out the clutch quickly to slow the engine RPM to a stop, without moving the vehicle.
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Old 04-17-2010
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Before you start pulling parts off the engine, I wouldn't get too worried about her. She started and responded to the throttle. Did she make any nasty noises? If not, good enough. As a general rule of thumb, if a diesel starts easily, she is in decent shape. It is when she won't start easily that you have to start looking at fuel and/or compression related issues, like rings, valves, pumps injectors etc.

Replace the impeller and call up Torresens and order one of these:

Yanmar 2GM Major Kit Torresen

just for peace of mind. Jones's Rule #32 of Boat Maintenance- you will never require any of the spare parts you have on board, but the one part you don't have is always the one that fails, so always stock one of everything.
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Old 04-18-2010
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Raw water impeller looks good to go...

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1971 Contest 33 Hull Number 24

"Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover."

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Last edited by krozet; 04-18-2010 at 12:56 PM.
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Old 04-18-2010
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With everything put back together I decided to try something. So I ran a line from a bucket of water to the raw water pump. The bucket was filled with fresh, clean water and a garden hose to keep filling it. With water flowing into the bucket and filling the tube with water I turned on the engine. It started up without a struggle at all.



I turned it on and let it idle for about 4 minutes and then pulled the RPM's up for a couple minutes. Then I lowered the RPM's down and let it idle for another 5 minutes before turning it off. Everything ran like a champ! Water came out the exhaust and there was no black, blue or white smoke, there was very little in the way of exhaust at all (other than the water). Problem 1 is that the RPM's don't show up on the tach so I gotta fix that.

I left the transmission in neutral as I have not topped up the fluid yet but all in all I feel like I had a successful couple days.

[/b]So Should I have a mechanic come in to do a tune up?[/b] All signs are good so far as the engine didn't hesitate at all, turned on with no issues, stopped with no issues. No loud noises, no chuging, ran smoothly as I throttled up and down...
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1971 Contest 33 Hull Number 24

"Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover."

Mark Twain
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Old 04-18-2010
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If it ain't broke....
There really is no such thing as a tune up on a diesel- there are no plugs to change, no distributor cap or rotor, the only timing is the injection pump, and if it is working it is working. it either runs well with no smoke, no hesitation and no bogging or it doesn't, fiddling with a decent running engine won't do much. Make sure your fuel is clean, your fuel filter is clean, your coolant lines are clear, you raw water pump is good, the air intake is unobstructed, check the intake and exhaust valve adjustment, and run her. All of that you can do yourself in a coupe of hours with a manual. if you don't have a manual, and need the specs on valve clearance, let me know and I will scan the relevant pages from my manual.
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Old 04-18-2010
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I would agree with bljones recommendation. Once you have checked fluids and filters, the only normal adjustment required is the valves. This is something that you can learn to do quite easily if you have no previous experience. Very few diesels are designed as interference engines so even a valve that is badly out of adjustment is usually not a big problem.
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Old 04-27-2010
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Looks pretty familiar

This looks very familiar. My air cleaner cover looked very similar. I replaced the filter element and cleaned the housing with some solvent. I believe that the 'gunk' pictured in your photos are both 'dust' from the breakdown of the sponge in the filter element, and adhesive used by the manufacturer (on the metal screen) to adhere the foam to the screen. Nice to know that much of your sponge filter element probably went through your diesel before the previous owner tore it out, now allowing all sorts of even bigger particles to go through the motor. My engine ran, but I pulled the injectors and had them rebuilt. The company that serviced them remarked that they were surprised that the engine started at all, the injectors were so filthy. Even still, my engine only seemed to banging on 2 of three cylinders, which I discovered when I had to bleed the injector lines. After rebuilding my injector pump and adjusting the governor, my engine now runs perfectly. There's another post where I discuss a subsequent upgrade to my exhaust mixing elbow, after it failed at (of course) an inconvenient time.

Ah, the joys of rehabilitating an old diesel!!
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