I found this: One of the few maintenance procedures possible is to free the center plunger in case it is frozen in its channel. This will not necessarily fix the problem, but may only change the symptoms. A stuck plunger is typically observed as an air input metering flap that is either frozen in the closed position, or never develops any pressure with the engine running, and the very rich condition mentioned above.
With the fuel distributor removed from the engine, pull on the plunger with needle-nosed pliers. The plunger is VERY hard so this will not damage it. If the plunger does not come out with some effort, STOP and get another fuel distributor. If the plunger does come out, clean it up with solvent, use some cotton swabs to clean out the passage (DO NOT pour solvent into the unit!) and reassemble. CAUTION: dropping the plunger on a concrete floor will damage it and it will no longer move freely in the bore. Be careful!
My air metering flap moves up and down freely. Is it possible to test the air metering plate pressure if the engine wont start? I need to remove the fuel distributor to see if the plunger moves freely correct? Can I see the plunger once the fuel dist is removed?