V6 petrol automatic will not even turn over or start.

High I have arover 75 conoseur automatic v6 petrol car that in one day whent from intermitent sarting to not starting at all I have replaced the camshaft sensor, the crankshaft sensor, the ignition switch, and finally I a rechonditioned starter motor. But still it wont turn over.
when I turn the key the instuments light up I hear burring sounds as normal and a couple of clicking sound then when I turn key to start position nothing hapens at all. The verry last time I drove it the speedo failed.