SailNet Community - Reply to Topic

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance > How to do compression check?
 Not a Member? 


Thread: How to do compression check? Reply to Thread
Title:
  

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

Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:
 

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:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below


Additional Options
Miscellaneous Options

Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below


Topic Review (Newest First)
08-04-2012 10:14 AM
dsmauney
How to do compression check?

Thanks Iron. Neat idea on oil fill cap. Appreciate other input.

Goodwinds
DaveM
08-04-2012 09:23 AM
IronSpinnaker
Re: How to do compression check?

Yes; use them. A Pre-chamber Diesel is designed with lower compression than a Direct Ignition Diesel, which is why they have glow plugs.

Ignition takes three things, fuel air and heat. In a Direct ignition diesel the compression of the fuel and air causes the heat for ignition. In a Pre-Chamber diesel glow plugs are used to gain the heat at a lower Compression. If you have glow plugs your engine was designed to be started with their use. It will start without them usually, but it will be much harder and that is normal.

You can see blowby if you remove the oil cap, you would have exhaust coming out the fill spout. That would be a very good indication that engine has significant wear.
08-03-2012 06:44 PM
Geoff54
Re: How to do compression check?

Quote:
Originally Posted by dsmauney View Post
Thanks Barry.

What I am asking Iron is the following. When he offers the opinion that a responsive start on a cold engine is a sign of good compression does that include using glow plugs on engines, like the M25xp, that have them. Response from anyone that has experience with diesels would be appreciated.

Goodwinds
DaveM
Yes - if you have glow plugs, use them. An engine with poor compression will usually be harder to start and often idle unevenly, although both conditions can be caused by other things.
08-03-2012 04:17 PM
BarryL
Re: How to do compression check?

Quote:
Originally Posted by dsmauney View Post
Thanks Barry.

What I am asking Iron is the following. When he offers the opinion that a responsive start on a cold engine is a sign of good compression does that include using glow plugs on engines, like the M25xp, that have them. Response from anyone that has experience with diesels would be appreciated.

Goodwinds
DaveM
Yes. If an engine has glow plugs, they should be used for a cold start test.

Barry
08-03-2012 03:09 PM
miatapaul
Re: How to do compression check?

Quote:
Originally Posted by IronSpinnaker View Post
They actually only tell you anything if done on a schedule with the data trended on a graph. All engines have wear metal present in the oil. The presents of wear metal means the engine works. The oil analysis only shows you the rate of deterioration if you have multiple points of reference over time.(like at scheduled oil changes) 10, 20, or 30 % increase in wear metal in a three months scheduled oil change is normal.... 100% increase in the same amount of time is bad.
They can tell you if something is out of wrack. Blackstone has a pre-purchase test kit (includes a pump to get oil out) and will give results same day they receive the sample. I agree it is not as good as a trend, but it could find coolant from a small leak in the head gasket, the most common issue. It will show very high levels of metals if there is a bad bearing. It can also indicate if the oil has not been changed in a long time. There is a lot of info in there. I have no interest in Blackstone, but have used there services in the past and found it to be useful information.
08-03-2012 02:16 PM
dsmauney
How to do compression check?

Thanks Barry.

What I am asking Iron is the following. When he offers the opinion that a responsive start on a cold engine is a sign of good compression does that include using glow plugs on engines, like the M25xp, that have them. Response from anyone that has experience with diesels would be appreciated.

Goodwinds
DaveM
08-02-2012 03:41 PM
BarryL
Re: How to do compression check?

Quote:
Originally Posted by dsmauney View Post
Iron

So if I understand what you are saying, a cold start with a diesel with pre-chambers ( universal M25xp) includes using the glow plugs?

Thanks
DaveM
Hi Dave,

I have an Universal M25. It has glow plugs and I always use them if the engine is cold. If the air temp is cold, like 50 degrees F, I energize the glow plugs for 1 minute. It the air temp is hot, like 80, 10 seconds of glow plug is enough.

The M25 glow plugs are designed to heat the combustion chamber. No fuel is injected at this time. The glow plug is just a heating element that is used to raise the temperature of the combustion chamber before the engine is running. It's pretty easy to remove a glow plug and test it - just supply 12V and it should glow red pretty quickly. Make sure to use at least 10 gauge wire because it draws a good amount of current.

Last but not least, many boats with M25 engines are wired so that the starter doesn't get power unless the glow plug is powered too. So you need to press both the glow plug button and the start button to start the engine.

Barry
08-02-2012 10:53 AM
dsmauney
How to do compression check?

Iron

So if I understand what you are saying, a cold start with a diesel with pre-chambers ( universal M25xp) includes using the glow plugs?

Thanks
DaveM
08-02-2012 06:38 AM
IronSpinnaker
Re: How to do compression check?

Quote:
Originally Posted by BarryL View Post

The glow plugs on my engine didn't work well (bad wiring) so the engine was hard to start.

Barry
Just so nobody is confused there are different types of diesel engines. The engine we are talking about in this thread is direct ignition and has no glow plugs.

Many modern small diesel engines are what is called pre-chambered diesel engines and they have glow plugs that pre-heat the fuel/air mixture in a small chamber prior to delivering it to the cylinders. They operate at lower compression and usually will not start if the glowplugs are not functioning.
08-01-2012 09:54 PM
BarryL
Re: How to do compression check?

Hey,

You should ask your surveyor how he will evaluate the engine. When I had my boat surveyed (in 2006) he said he would check all fluids (engine oil, transmission oil, coolant), check all hoses (fuel and coolant), perform a visual evaluation, and then test it during the sea trial. The sea trial included running it at wide open throttle (WOT) for a minute to make sure it didn't overheat (it didn't) or smoke (it did - due to being overpropped), and make rated rpm (it didn't, again because of the prop). He also performed an emergency stop to test the engine mounts.

The glow plugs on my engine didn't work well (bad wiring) so the engine was hard to start. It had 3600 hours at the time of the survey. I wasn't concerned because the engine ran fine, and I only put about 50 hours a year on it. It now has about 3900 hours and has worked very well.

Here is the surveyor's report on the engine:

ENGINE OPERATION
The engine started easily after pre-heat and ran without smoke. The volume of cooling
water was good. There was no oily residue on the water.
Due to the tachometer problems it was not possible to see if the engine ran up to the
manufacturer's specification of 3200 RPM. At wide open throttle the boat speed,
measured by GPS, was 6.7 kts, below the theoretical hull speed of 7.3 kts.
Engine temperature at WOT was 180°F. The temperature differential between the raw
water and the exhaust was 20º at cruise and 30° at WOT. No hot cylinders were noted.
The alternator was charging at 14.35V.
The engine ran without significant vibration. The emergency stop test did not disturb the
engine mounts.


==

Barry
This thread has more than 10 replies. Click here to review the whole thread.

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


All times are GMT -4. The time now is 01:51 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.