Engine: Compression Test - Revision history

Stealthify: Added common problems + wet test + additional info to help members understand their readings

2013-03-09T01:51:35Z

Added common problems + wet test + additional info to help members understand their readings

Stealthify: Rebuilt tutorial using new photos and improved grammar/structure/instructions

2013-03-07T05:47:28Z

Rebuilt tutorial using new photos and improved grammar/structure/instructions

Stealthify: Created page with "Category:How To Category:Engine A compression tester is a gauge that screws into the spark plug holes so that cylinder compression can be measured. For the most part,..."

2012-06-30T02:11:42Z

Created page with "Category:How To Category:Engine A compression tester is a gauge that screws into the spark plug holes so that cylinder compression can be measured. For the most part,..."

New page

[[Category:How To]]
[[Category:Engine]]

A compression tester is a gauge that screws into the spark plug holes so that cylinder compression can be measured. For the most part, they are universal for gas power engines.

[[Image:Craftsman_compression_tester.jpg]]

This particular model can be purchased from Sears for around $60.00.

==Steps to Perform a Compression Test==
*Next you need to disable the cars ability to start this can be done one of two ways.
#Remove the [[ECI]] fuse
#Disconnect the coil wire for [[SOHC]]. Disconnect the [[Crank Angle Sensor (CAS)]] for [[DOHC]].
*You have to pull the intake manifold off to do the back 3 cylinders. If you just do the front just pull out the intake arm then have someone hold the [[Throttle Body]] wide open.
*Remove the Spark Plugs.
*Crank the starter for about 5 [[Compression]] strokes (you can see the gauge move 5 times).

Then it will either tell you a high number (good) or a low number (very bad). It is possible to have good numbers on some cylinders, but one or more with a very low number.

{| class="wikitable" style="text-align:center" border="1" cellpadding="0" cellspacing="0"
|+Standard Compression Numbers (PSI)
|-
! !! Standard (New) !! Lower Limit
|-
!SOHC
| 171 || 127
|-
!DOHC NA
| 185 || 139
|-
!DOHC TT
| 156 || 115
|}

@@ Line 31: / Line 31: @@
 |}
-# '''Warm the engine up'''. To get accurate readings, it is best to perform the test on a warm engine. ''Warning: use caution while completing the following steps, as some engine parts will be hot!''
+# '''Warm the engine up'''. To get accurate readings, it is best to perform the test on a warm engine. A cold engine will provide lower than expected results. ''Warning: use caution while completing the following steps, as some engine parts will be hot!''
 # '''Disable the car's ignition system'''. This is an important step that prevents the fuel injectors from firing, allowing you to safely turn over the engine to perform the test. You can do this one of two ways:
 #* Remove the [[ECI]] fuse, or
@@ Line 49: / Line 49: @@
 # '''Compare your PSI readings to the table to the right'''.
 # '''Repeat the previous four steps for each cylinder you wish to test'''.
@@ Line 55: / Line 58: @@
 == Understanding Your Compression Reading ==
-Once you perform the compression test, the gauge will read either a higher number (which is usually good), or a low number (which is very bad). It is possible to have good numbers (high) on some cylinders and bad numbers (low) on the others, as the compression of each cylinder is independent of eachother. Ultimately, there should be no more than 14 PSI difference between the highest and lowest cylinder compression readings.
+{| class="wikitable" style="float:right;margin-left:20px;"
-A low reading is usually a good indicator of an existing problem. When you receive a low reading, your next step should be to check if the pressure leaks downwards (piston/cylinder) or upwards (valve) and then invest in the necessary repair.
+A low reading is usually a reasonable indicator of an existing problem. When you receive a low reading, your next step should be to perform a [[Engine:_Perform_Leak-down_Test|leak-down test]] to check if the pressure leaks downwards (piston/cylinder) or upwards (valve) and then invest in the necessary repair.

@@ Line 1: / Line 1: @@
 [[Category:How To]]
 [[Category:Engine]]
-A compression tester is a gauge that screws into the spark plug holes so that cylinder compression can be measured. For the most part, they are universal for gas power engines.
+In order to perform a compression test on your engine, you will need a compression tester. This kit consists of a gauge and an extension tube with adapters, which screws into the spark plug hole in order to measure the compression of the cylinder you wish to test.
-[[Image:Craftsman_compression_tester.jpg]]
+Compression testers are generally universal for gas powered engines, so you do not need one specific to the [[Mitsubishi_3000GT/Dodge_Stealth|Mitsubishi 3000GT or Dodge Stealth]]. They can easily be purchased from AutoZone or Sears.
-==Steps to Perform a Compression Test==
+==== Tools Required ====
-*Next you need to disable the cars ability to start this can be done one of two ways.
+* 8mm socket w/ wrench
-#Remove the [[ECI]] fuse
+* Compression tester kit
-Then it will either tell you a high number (good) or a low number (very bad). It is possible to have good numbers on some cylinders, but one or more with a very low number.
+<br style="clear:both;" />
+== Perform a Compression Test on a Mitsubishi 3000GT and Dodge Stealth ==
-{| class="wikitable" style="text-align:center" border="1" cellpadding="0" cellspacing="0"
+[[Image:Compression_Tester_Gauge-Reading.jpg|thumb|right|240px|Compression test being performed on a Mitsubishi 3000GT/GTO or Dodge Stealth]]
-|+Standard Compression Numbers (PSI)
+{| class="wikitable" style="text-align:center;clear:right;float:right;margin-left:20px;" border="1" cellpadding="0" cellspacing="0"
 |-
-! !! Standard (New) !! Lower Limit
+! !! Standard !! Minimum
 |-
-!SOHC
+! SOHC
 | 171 || 127
 |-
-!DOHC NA
+! DOHC NA
 | 185 || 139
 |-
-!DOHC TT
+! DOHC TT
 | 156 || 115
 |}