The OP has a 1982 4/4. No ECU and 32/36 DGAV (or a DGV and a manual choke).
A carburettor engine always has fuel, even if fitted with an electric pump as the float chamber has enough fuel to propel the car 100 yards. Shouldn't matter with a petrol engine as the key turns the spark off and petrol engines should then stop.
Can't see inside the engine, but basically, something is acting as an ignition source. Carbon build up is almost certainly the issue. Known not unsurprisingly as dieseling.
No idea what the car was, but one Ford had the problem so much they made an 'anti-diesling valve' that admitted air to the cylinders when the ignition was off. Engineering wise, complete and utter bodge in my book.
