4.0L Compression Test Results - JeepForum.com

 
LinkBack Thread Tools
post #1 of 5 Old 10-18-2009, 01:25 PM Thread Starter
Runner6
Registered User
1991 XJ Cherokee 
 
Join Date: Mar 2007
Location: NC
Posts: 47
4.0L Compression Test Results

The 4.0L is actually in a 1987 MJ, but I thought I'd post it here as well. Hope to get some expert advice.

Had the fuel pump and all fuel injectors professionally replaced, and just completed a compression test. Here's what we came up with:

1 - 65 psi
2 - 90 psi
3 - 90 psi
4 - 60 psi
5 - 90 psi
6 - 80 psi

Although the engine only shows 97K, it was not well-maintained by the previous owner. We changed the oil immediately upon purchase, and the oil was the blackest I've ever seen. It even felt sticky. No telling when the last oil change took place.

Any opinions on what the readings above are telling us?

Thanks.

Runner6 is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 10-18-2009, 01:43 PM
blue96jeep
Registered User
1996 XJ Cherokee 
 
Join Date: Jan 2008
Location: Queens
Posts: 677
if i am not mistaken the spec is 120-150 since your specs are below the minimum spec i say you need to rebuild, piston rings are shot, did you do a wet test.

-ryan
blue96jeep is offline  
post #3 of 5 Old 10-18-2009, 02:36 PM
Rollin
Registered User
1998 XJ Cherokee 
 
Join Date: Feb 2007
Location: NH
Posts: 1,249
Quote:
Originally Posted by Runner6 View Post
The 4.0L is actually in a 1987 MJ, but I thought I'd post it here as well. Hope to get some expert advice.

Had the fuel pump and all fuel injectors professionally replaced, and just completed a compression test. Here's what we came up with:

1 - 65 psi
2 - 90 psi
3 - 90 psi
4 - 60 psi
5 - 90 psi
6 - 80 psi

Although the engine only shows 97K, it was not well-maintained by the previous owner. We changed the oil immediately upon purchase, and the oil was the blackest I've ever seen. It even felt sticky. No telling when the last oil change took place.

Any opinions on what the readings above are telling us?

Thanks.
Supposed to be 150 on a 4.0l. Time for a rebuild with 4.2 rods and a 4.2 crank

1998 Jeep Cherokee Classic: Bull Bar, TracLock Chrysler 8.25"
Rollin is offline  
post #4 of 5 Old 01-09-2010, 10:46 PM
KevinM90
Registered User
1998 XJ Cherokee 
 
Join Date: Jul 2008
Location: Maine
Posts: 262
rings and head gasket?

1996 Jeep Cherokee Sport. 3" lift/31" combo. Some lights. Flowmaster. 5 different horns. Full size spare. No rust. Daily driven. Will be...forever.

Last edited by KevinM90; 01-10-2010 at 12:02 AM.
KevinM90 is offline  
post #5 of 5 Old 01-09-2010, 10:49 PM
KevinM90
Registered User
1998 XJ Cherokee 
 
Join Date: Jul 2008
Location: Maine
Posts: 262
double post sorry

1996 Jeep Cherokee Sport. 3" lift/31" combo. Some lights. Flowmaster. 5 different horns. Full size spare. No rust. Daily driven. Will be...forever.
KevinM90 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

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 e-mail address for yourself.



Email Address:
OR

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.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
Compression Test Results! 1984XJ XJ Cherokee Technical Forum 5 07-24-2009 07:59 PM
advise needed on compression test results and headgasket crmaverick89 XJ Cherokee Technical Forum 12 07-19-2009 10:52 PM
bad compression results StokedXJ11 XJ Cherokee Technical Forum 1 10-04-2008 03:17 PM
Compression Results XJ4oh XJ Cherokee Technical Forum 0 07-06-2008 03:53 PM
Compression Test Results oj_584 XJ Cherokee Technical Forum 9 05-02-2007 02:17 PM

Posting Rules  
You may post new threads
You may 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
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome