Is this car a V-12?
If it is, and you have the Marelli type ignition, or similar, check the rear magnetic pick-up that counts the teeth on the flywheel.
The connector will be a two pin connector along the firewall, most likely on the l/h side. Check the connector for corrosion.
The front pickup is used more for after the engine runs. If the cable for the rear pick-up has come into contact with the exhaust, it will burn and short out. The engine will run, but it will not start.
Good luck