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Forum namePerformance/Engine
Topic subjectcompression test question
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i5&topic_id=46502
46502, compression test question
Posted by nappyjim, Mar-11-03 10:36 PM
Just got a kinda stupid question on testing my compression. I know i unhook all spark plugs wires and take out all 4 plugs. Then disconnect the ignition system.

But then i get confused and my stupid questions come in. With the igntion system disconnected...the car will not start obviously....right?

So reading Chiltons it says to have someone else fully press the gas pedal (WOT) . Do i then have them attempt to start the car while pressing the gas down all the way? or what?
46505, RE: compression test question
Posted by Matt_95tgs, Mar-12-03 01:04 AM
First, you want to start the car and let it get up to operating temp and shut it off. Next, take off all of the spark plug wires and spark plugs. Now disconnect the 2 relays on the drivers side of the firewall. Those 2 relays control the ignition and the fuel pump. By disconnecting these, the engine will not see any spark or fuel. Now, screw in the compression tester so its snug (do not tighten with a tool, only hand tight) and crank the motor over for about 5 seconds. Repeat the last step with the remaining 3 cylinders and thats all there is to it.
46506, RE: compression test question
Posted by nappyjim, Mar-12-03 01:29 AM
so i dont neeed to be at wot when crankin?
46512, RE: compression test question
Posted by 98Talon, Mar-12-03 04:02 AM
being at WOT will do you no good since you have no fuel or spark anyway, just turn over the motor. Also, I prefer to do the plugs one at a time while I change them rather than pulling them all out. This is because I'm the kind of dumbass who'd accidentally drop a rock or something down in one of the plug holes.
46615, RE: compression test question
Posted by Remy, Mar-13-03 09:30 AM
Crank motor 5-6x and just make sure you dont get the plug wires mixed up.

95 gs-t
To much shit to list !!

Pic coming in a few weeks.
46630, RE: compression test question
Posted by XtremeRS, Mar-13-03 11:31 AM
You actually want to have ALL plugs out when you do a comp test, as this gives more accurate readings. If you do this alone, set the comp tester so that you can see the needle when you crank it over. As you crank it, look at the gauge and stop cranking when the needle moves up no more. This is important! If you stop cranking too soon, then you may not get the total compression, as it might have been still builing up. Usually will take about 5 compression strokes of the piston to get to its full reading. And no, its not necc to hold the gas to wot. It may only benifit to help build compression a tad bit faster (less cranking).