A Cosworth management system usually has it "cam" sensor inside the distributor.
Are you sure you are referring to the correct "cam" sensor?, because without a signal telling what cylinder 1 is, the engine will not start.

Use an ohm meter (Digital Volt Meter) to measure resistance.
Disconnect connectors and measure between the two pins of the injector.
Or remove the complete fuel rail with injectors, wiring, pressure regulator and fuel lines.
Then have somebody start the engine and observe spray pattern on all injectors.
All 4 injectors spray fuel? Roughly the same amount?

If you remove the spark plug from the first cylinder: is it soaking wet or bone dry?
Is the chip in the P8 mapped for your engine?