Hi, I have a 1990 420se, I have noticed that there is no advance or retard shown when using a timing light.........any clues techies

What exactly are you doing?

If you blip the throttle, you should see the timing advance quickly and then return. If you increase the RPM gradually you should see the timing advance as RPM goes up. If this doesn't happen, you probably have an (expensive) problem with the ignition module.

But you should not see the timing change when turning the distributor, because it is controlled by the ignition module.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe