If you undo the three screws holding the fuel distributor to the metering plate you can lift it off and get to the plunger. It should move up and down freely. If not, carefully remove it and clean it and the inside with carb cleaner.
Some cautions, in case you don't know:
Do not use any tools on the plunger. They are precision milled to fit exactly (so much that you can't usually swap them between fuel distributors), so any damage will ruin the whole thing.
Do not try to remove the barrel (where the plunger rides), as misaligning it will cause the distributor to leak or not work at all.
Just take the distributor off, clean the plunger, put it back.
I'm sure that's all it is.