Compression testing

Jump On It · 03-11-2010, 02:17 PM

Harry,

A Group K article states something like this: contrary to popular belief keeping a spark plug in the other cylinder not being tested will allow the motor to spin faster during testing. I believe this to be true and do it this way also but I am trying to understand the logic behind this ? One would think there would be less labor on the starter with having the other plug out ?

Thanks for your input...

Big Vin · 03-13-2010, 03:48 AM

maybe the balance in pressures makes it spin more "even"?

Group K · 03-15-2010, 02:27 PM

There is disagreement among techs about why this happens .... but the tach tests we have done on every platform we tested with showed higher cranking rpms with the plugs "in" the holes not being measured ... and those added rpm speeds resulted in higher indicated readings (just another variable that complells us to not quote PSI compression numbers).

Respectfully, Harry Klemm

Quote:

Originally Posted by Jump On It

Harry,

A Group K article states something like this: contrary to popular belief keeping a spark plug in the other cylinder not being tested will allow the motor to spin faster during testing. I believe this to be true and do it this way also but I am trying to understand the logic behind this ? One would think there would be less labor on the starter with having the other plug out ?

Thanks for your input...