DM6 and upwards actually use an entirely different solenoid. Pictures in the manual aren't clear (I don't actually own a PM6 myself), but they also appear to show the new type solenoid, and the PM7 definitely uses it.
DM4, DM5 and PM5 use the same solenoid as the Quest. Newer DMs and PMs don't.
As for the issue, I believe the ring that you are describing is a 'slip' ring, rather than an o-ring. It is an alignment guide rather than a seal, and these generally do have a gap in the circumference.
Is your battery fresh?
Is your dwell high enough?
Is the trigger definitely depressing the microswitch on the board, and is the switch able to reset after you release the trigger?
Do you have a spare harness that you can install? Quest harnesses are renowned for being brittle and breaking.
Last edited by Uziel Gal : 06-03-2011 at 10:05 AM.