Alfa 33 starting problem

[alfatect]

33 Quattro refuses to start. Has new spark plugs, fuel and a weak spark. Have substituted replacement coil, distributor cap and HT leads. I have a spare electronic distributor but the wires from the pulse generator have lost all the insulation down to the moulded plug, so guess it won't be much use. I suspect distributor and timing, but advancing and retarding distributor doesn't help. Any ideas welcome, or access to a distributor to isolate the problem - Marelli SM 802 AX or SM 818 AX 5B or Bosch 0.237.005.004 or JGUD 4. Thanks, Laurie Jones