Return to the home page...

Go Back   Moyer Marine Atomic 4 Community - Home of the Afourians > Testing Protocols

Reply
 
Thread Tools Display Modes
  #1   IP: 24.152.132.140
Old 07-17-2019, 10:16 PM
ndutton's Avatar
ndutton ndutton is offline
Afourian MVP
 
Join Date: May 2009
Location: Torrance, CA
Posts: 8,698
Thanks: 153
Thanked 1,297 Times in 872 Posts
Compression Test Notes

Compression test details from another thread:
Quote:
Originally Posted by Dave Neptune View Post
. . . . . . . Do a compression check again and then do another with a bit of oil sprayed into the cylinders like Al suggested.

Be sure the choke is open, the throttle is wide open, spark plugs removed and the ignition lead disconnected for a proper compression check.

Dave Neptune
__________________
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
Reply With Quote
  #2   IP: 71.38.107.125
Old 07-18-2019, 10:56 AM
roadnsky's Avatar
roadnsky roadnsky is offline
Afourian MVP
 
Join Date: Dec 2008
Location: Lake Mead, NV
Posts: 2,894
Thanks: 19
Thanked 234 Times in 168 Posts
I think I also got this from Dave:

Test the engine while its warm, as you'll get different readings hot and cold.
Your readings will be higher on a hot engine, but if it passes cold it will pass hot.

1. Make sure water intake is shut off so you don't fill exhaust system with water which will then enter the cylinders.
(You're not actually going to run the engine during the test so it won't need any cooling)
2. Remove spark plugs. Cover holes with a rag.
3. Remove coil wire, disable fuel pump if electric (remove fuse or disconnect wire)
4. Open throttle to wide open and leave it there.
5. Be sure choke is OPEN completely
6. Screw tester into spark plug hole 1 and crank engine with starter for a few seconds.
You'll see the pressure on the gauge go up in steps and max out. When it tops out, that's the reading.
7. Repeat on other cylinders.

If the readings are low or vary more than about 10% from one cylinder to the next, add a tablespoon of motor oil through the spark plug hole of the low cylinder(s).
If this increases the pressure significantly, it indicates worn rings or valve guides (the oil acts to seal the gap somewhat).
If it doesn't change it's more likely a valve that's sticking or not closing all the way.
__________________
-Jerry

'Lone Ranger'

1978 RANGER 30
Reply With Quote
The Following 4 Users Say Thank You to roadnsky For This Useful Post:
Dave Neptune (07-18-2019), GregH (07-19-2019), Sam (07-18-2019), thatch (07-18-2019)
  #3   IP: 107.77.97.92
Old 07-18-2019, 01:09 PM
lat 64's Avatar
lat 64 lat 64 is offline
Afourian MVP
 
Join Date: Oct 2008
Location: Fairbanks, Alaska
Posts: 1,905
Thanks: 30
Thanked 172 Times in 115 Posts
I can add one more thing to the list:

Make sure the cranking battery is up to charge for all the tests. Even a change in cranking rpm can affect accurate comparisons of each cylinder's pressure readings.
__________________
Whiskeyjack a '68 Columbia 36 rebuilt A-4 with 2:1

"Since when is napping doing nothing?"
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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 Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Valid Compression Test jkenan Troubleshooting 11 12-18-2013 10:14 PM
Compression Test Procedure seapadrik Overhaul 2 07-15-2011 02:50 PM
Compression test and general questions mpahl Overhaul 6 03-22-2011 03:20 PM
compression test while partially disassembled boater tom General Interest 0 11-09-2008 12:29 PM
Compression test baileyem General Maintenance 2 06-18-2007 04:16 PM


All times are GMT -4. The time now is 08:48 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2019, vBulletin Solutions, Inc.


Universal® is a registered trademark of Westerbeke Corporation

Copyright © 2004-2019 Moyer Marine Inc.

All Rights Reserved