SL6 will not start with the key.

Pump eccentric is integral to the cam, not bolted on. hollow-log knock-knock-knock could be the fuel pump; run the engine long enough to fill the carburetor, shut it off, unbolt the fuel pump and run it again. If the knock goes away, it was the pump. If it's really bothering you, pursue it; if not, leave it be, it's not hurting anything. Knock can also be camshaft walk. Knock can also be faulty (sagged/old or sloppy/new) motor mount(s). Good luck with the pump replacement; many of the ones presently available are junk from China. Carry a fire extinguisher!