Go Back   986 Forum - for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Performance and Technical chat

Reply
 
LinkBack Thread Tools Display Modes
Old 04-06-2019, 08:32 AM   #1
Registered User
 
Join Date: Oct 2009
Location: Florida
Posts: 10
Weird compression test results 2000 986 S

Canít make out what it could be, The needle on the gauge does not move when cranking but when you push air into the cylinder, it holds pressure and you canít hear it leak out of the exhaust or throttle body. Took the oil cap off, no noise anywhere. Cyl #1 misfire on obd II. Changed coil and plug, nothing. Engine shakes badly, very down on power, raw fuel smell from exhaust. Quit working under light load at 2000 rpm, just cruising. Iím lost, any ideas???
kiosko is offline   Reply With Quote
Old 04-06-2019, 08:55 AM   #2
Who's askin'?
 
maytag's Avatar
 
Join Date: Mar 2018
Location: Utah
Posts: 1,272
Quote:
Originally Posted by kiosko View Post
Canít make out what it could be, The needle on the gauge does not move when cranking but when you push air into the cylinder, it holds pressure and you canít hear it leak out of the exhaust or throttle body. Took the oil cap off, no noise anywhere. Cyl #1 misfire on obd II. Changed coil and plug, nothing. Engine shakes badly, very down on power, raw fuel smell from exhaust. Quit working under light load at 2000 rpm, just cruising. Iím lost, any ideas???
How are you pushing air into the cylinder? Are you using a leakdown tester? If yes, does the needle move THEN?


Sent from my SM-G970U using Tapatalk
maytag is offline   Reply With Quote
Old 04-07-2019, 02:07 AM   #3
Registered User
 
Join Date: Oct 2009
Location: Florida
Posts: 10
Quote:
Originally Posted by maytag View Post
How are you pushing air into the cylinder? Are you using a leakdown tester? If yes, does the needle move THEN?
I used a tire fill rigged to the same hose of the compression tester. The tire fill gauge goes up to 100 psi and no air escapes out the exhaust or through the intake. Not a leak down check per say but i think it would be similar in nature. Ready to call it dead, unless someone can help me figure it out.
kiosko is offline   Reply With Quote
Old 04-07-2019, 05:18 AM   #4
Who's askin'?
 
maytag's Avatar
 
Join Date: Mar 2018
Location: Utah
Posts: 1,272
I've seen this once before, on a pushrod V8. I don't know why it wouldn't be plausible here as well. That motor had a broken valve spring, so when the motor was cranked, no compression. When air was introduced at 100psi, it was enough to slap the valve up into place and hold it there. I surmised then that this is one reason why a leakdown tester has a valve that allows one to introduce air more gradually.

If I were you, I'd get a borescope in there and have a look around.

Sent from my SM-G970U using Tapatalk
maytag is offline   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 On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -8. The time now is 08:05 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page