306 HDi won't stop

[philt]

A few more checks - tried disconnecting the alternator small single wire and heavier pair. Separating the two heavy wires will stop the engine which makes sense looking at the manual (removes supply from fuel pump). Re-connected alternator and started looking at ignition switch. With engine running disconnected the ignition switch completely - no effect,engine still running. This should remove supply to coil of ecu relay. The fuel pump relay appears to be switched by the ecu (pin 87) through the inertia switch. So, disconnected inertia switch with engine running, no effect, engine still running! However, with inertia switch disconnected engine now stops on the key, and will re-start ok. The only difference is a noise from the fuel filter housing suggesting that the pump is running while ignition is on (should pulse).
Any thoughts anyone.......................