Skip to main content
Gerry | Vanagon
Checking account...
← vanagon.com home · Continue the discussion in the forum
Subject:Re: How to Test Compression in Out-of-Vehicle Engine?
From:Bulley-Hewlett & Associates
Date:Tue, 6 Oct 1998 14:56:54 -0400

Can any Listee tell me a method for a DIYer ( do it yourselfer) to test the
compression in an out-of- vehicle engine?  Assume that I have a compressor,
and a compression gauge.
Thomas-

Simple. In a bug shop where I used to work, we built a lot of motors. We
chose to "hot run" the motors for a half hour before installing them so we
could re-torque the heads and adjust the valves after a heat/cool cycle.
Required the precise set-up you need.

You will need a dud tire (off the rim), a working starter, and bell housing
to fit your motor. You *may* be able to borrow same from a local bug shop,
or possibly a junkyard.

Set the motor on the tire. Not sure if you have exhaust system on or off.
This set up (tire on the floor) is designed for the exhaust system ON. Hook
jumper cables up to your car or van's battery, ground the black jumper
cable solidly to the testing engine block.

You MUST now have someone hold the motor, as it may want to scoot around as
you crank it. Carefully touch the red Jumper cable to the two points on the
back of the starter to engage the solenoid and rotate the starter. Be
prepared for a BIG spark when you do this, hold the cable tip firmly to the
points on the back of the starter to prevent further arcing.

Follow all the regular compression test frabbitz: (block throttle open,
partially remove the spark plugs, using the starter as described--turn
motor over for 10 revolutions or so, fully remove plugs, using the starter
as described--compression test each cylinder, drink a beer, scratch
yourself, replace plugs).

Hope this helps.

G. Matthew Bulley
Principal
Bulley-Hewlett & Associates
Communications for Organizational Development
www.bulley-hewlett.com
(888) 468-4880 toll free