If a pd Diesel engine starts easily and quickly when cold but struggles to start when hot, this is described as a Hot Start Problem.

 

These diesel engines are started by an ECU and not by the driver. Pressing the accelerator pedal has no effect during a starting procedure. Starting is actually controlled by a ‘starting map’ in the ECU and is based on starter/engine speed (rpm) and injected fuel quantity (iq).

 

Generally, the ECU will not allow start fuel injection until the engine rpm is above a fixed map value.

Such problems can occur from low battery charge, engine coolant temperature sensor faults or the starter motor itself.