[Public-List] Diesel Help

[Tim Adelman]

There are two types of compression checks.  For lack of a better description, a dry and wet check.  Essentially, you do a compression check and record the numbers.  Then add a little oil to the cylinders and repeat.  IF the numbers go up, then the decrease in compression is due to space between the piston ring and the cylinder wall.  This will require at least a top end overhaul.  

If the number stays the same, then the culprit is likely a valve.  While this still requires attention, it is a lot less expensive.  I would find out if they did both to verify the decrease in compression is P&C related and not valve related.

As for running the engine with low compression, it usually isn't a fatal event.  The engine will just get crappier and crappier over time in terms of starting, idle and power output.  Keep you starting strokes short.  During keep cranking for any one session too long.  Al has a diesel mechanic he has been happy with and is reasonable. I will get the info for you.

p.s. Since you are registered for the WNR in my name, try not to lose the engine at a critical time and hit the Spa Creek bridge.

-----Original Message-----
From: public-list-bounces at lists.alberg30.org [mailto:public-list-bounces at lists.alberg30.org] On Behalf Of Jonathan Adams
Sent: Monday, April 11, 2011 1:20 PM
To: public-list at alberg30.org; Alberg 30 Member List
Subject: [Public-List] Diesel Help

Well I finally have a question that I really need an answer to - versus one where I am looking for an opinion!

I have a Yanmar 2GMF. It is between 20 and 25 years old, and for the last couple of years has been having a hard time starting - I might have to crank the engine for a number of extended periods - minutes. This spring, I had Bayshore Marine look at the engine, and they checked injectors and performed a compression test. 
The injectors are fine, and the engine once started runs well. If it is warm, it starts immediately no problem. Once running, it can hit its top revs (~4k+) under no load - which indicates that the fuel pump / timing is good.

The result of this visit - other than lightening my wallet - was that the lack of compression was creating the problem. It is meant to be 469lbs and is 400 in
#1 and 415 in #2. The only way to deal with this is to check either the head or the piston rings. Either way it is an expensive proposition. can I get it to last the season? It is only a matter of time before I burn out the starter motor and / or drain my batteries.

The mechanic recommended:

1. release the compression on the cylinders, and crank the engine to warm things up, and then start

2. While doing this close the water intake valve, as the  muffler has no exhaust to speak of when you are cranking and will fill up with water which could back into the engine.

3. He recommended putting CRC into the air intake to help seal the pistons. He did not recommend starting fluids as these damaged seals. Someone else has recommended putting in heavier oil.

Any advice from the crowd? If I send the engine to Bayshore, I essentially get a new engine, as they will warrenty it, and totally overhaul it while it is out. 
However, this is sure to seriously impact the boat fund. Any recommendations for a good mechanic that is not a crack head? The reason I went back to Bayshore was I kept running into crack head mechanics.

Jonathan
197
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