On my 1985 Subaru DL, the EA82 engine would start up and die at idle. Since this has been a problem that been slowly getting worse, and after checking for a vacuum leak, I assumed that there was a problem with the engine. So I did a compression test before removing the engine to see what kind of compression I was getting. I screwed in the brand-new compression tester into the first spark plug hole and cranked the engine in the proper direction to see what the reading was.

 

The result? No compression at all. The needle didn't move a damn bit, and it was the same for the other three cylinders too. I checked the compression tester orally, and was able to make the needle move faintly, so no problem there.

 

What I'm wondering is if it is common for an old engine that hasn't been overhauled for a long time to have no compression when cranked by hand, or was I just using the tester wrong? Right now the engine is in pieces, and im preparing to put new piston rings and gaskets in, and clean the valves real good etc. Pics upon request.

i don't think you'll get a compression reading by turning the motor over by hand in my experience. maybe different motors, testers are more capable but my standard off the shelf compression tester won't read anything when i turn my motors over by hand. zero. need to use the starter to get the motor turning.

i don't think you'll get a compression reading by turning the motor over by hand in my experience. maybe different motors, testers are more capable but my standard off the shelf compression tester won't read anything when i turn my motors over by hand. zero. need to use the starter to get the motor turning.

 

Ah well theres my problem. Thanks for the heads up.

I've also heard it recommended to have the engine warm, remove all the plugs, and block the throttle plate open to get the best results.

On my 1985 Subaru DL, the EA82 engine would start up and die at idle. Since this has been a problem that been slowly getting worse, and after checking for a vacuum leak, I assumed that there was a problem with the engine. So I did a compression test before removing the engine to see what kind of compression I was getting. I screwed in the brand-new compression tester into the first spark plug hole and cranked the engine in the proper direction to see what the reading was.

 

The result? No compression at all. The needle didn't move a damn bit, and it was the same for the other three cylinders too. I checked the compression tester orally, and was able to make the needle move faintly, so no problem there.

 

What I'm wondering is if it is common for an old engine that hasn't been overhauled for a long time to have no compression when cranked by hand, or was I just using the tester wrong? Right now the engine is in pieces, and im preparing to put new piston rings and gaskets in, and clean the valves real good etc. Pics upon request.

jst by a new motor its much esyer but da rings sound ************ed eny way

SOmetimes the engine cant be warm. Procedure is to remove all the plugs, and have a wide open trhottle. Crank the engine 7 times and repeat. Once you have done this, you squirt some oil in the cylider and do it alll aover again and record those numbers.If there is a increase in pressure, you have a weak rings, no change you a vavle or valve timing issue.

 

 

 

nipper

Valves properly adjusted? I put some cams in one of my vehicles once, forgot to adjust the valves, and was getting 0 comp all the way across. Just a thought...

Valves properly adjusted? I put some cams in one of my vehicles once, forgot to adjust the valves, and was getting 0 comp all the way across. Just a thought...

 

Non adjustable;)

 

 

Nipper nailed it on procedure though

Check your timing belts before you run the compression test. I bought a Subaru for $100 from a shop that claimed it had no compression. I replaced the timing belts, and the engine was fine. The timing belts determine when the valves open and close- if they're not right, you won't get accurate compression readings.

well if it is the timing belts, he will get low or no compresiion weather its a wet or dry test.

 

This is very easy test to do and will tell you whats what very fast.

 

 

nipper