How I do it:

Pull ALL the plugs so the engine will crank faster with less stress on the starter. DO NOT pull the plugs with the engine hot - too much risk of galling the threads in the head ($$$) due to differential expansion of the aluminum head and the steel plugs. Warm is OK.

If you can find the remote starter pickup use it. On my 83 and 81 it is the blue wire emerging from the harness on the firewall almost directly behind the cyl head. It has a red plastic sleeve covering the last few cm's of the wire before the connector at its end. Connecting this to battery+ cranks the starter. Battery must be in good shape.

Pull the coil wire out of the distributor and stick an old spark plug into that end. Ground the body of the plug to the PS or AC mounting bracket. Hold it in place with a twisted piece of mechanic's wire or coat hanger. This simulates ordinary ignition action as far as the primary and secondary ignition circuits can tell, and won't damage anything electrical.

Find something to block the throttle open about 1/4-way or so. You don't want the tested cylinder pulling against any vacuum.

If you can't find the above remote starter wire, remove the 25A fuse for the injection system relay, as you will be using the ignition switch.

The push-in compression gauges are very prone to "operator error" I wouldn't use anything but a screw-in type. These also allow a one-person procedure.

If you have the remote starter setup you can hold the gauge in your hand as you crank the engine. If not, you'll have to use the ignition sw. which means either a second person, or somehow place the gauge where you can see it from the driver's seat. You need to watch the pressure behavior, not just the max reading.

The gauge should get to its maximum on the fourth stroke. I've found it goes something like: 60%/90%/98%/100%. More cranking results in no more movement of the needle on a good cylinder. If the pressure does not rise as I've described - such as it seems to rise in smaller increments and takes 6-8 strokes to get to max - you have a leaky cylinder, probably around the rings. You only want about 15-20 psi max variation between best and worst cyl on a high mileage, but good condition engine. Less on a newer one. Have a piece of paper handy and WRITE DOWN the readings as you take them, and any remarks on how they arrived. You WILL forget which cyl was which. Short pencil beats a long memory.

Your pressure readings are not too meaningful in comparison to other people's. You are using a different gauge and different techniques than they did. But each of your cylinders saw the same gauge, the same techniques, and the same engine temp, etc. So don't worry if you get 150 psi and someone else gets 180. Worry if you get 150/150/100/150....and ask back here what it may mean.

Bob


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Bob (81-244GL B21F, 83-244DL B23F)