A list of Common Faults

Fault Will not start/difficult to start.
Cause Failed crankshaft sensor/High back leakage past injectors or split PCV seal
Repair Crank Sensor/Test Injectors/Replace seal on P.C.V.

Fault Loss of power and/or engine stalls
Cause Failure of the P.C.V. (Pressure Control Valve)
Repair Replace P.C.V. (No pump removal required)

Fault Fuel Leak from high pressure pump
Cause Deterioration of seals caused by bio-fuels.
Repair Replacement of seals (pump removal required)

Fault Cutting out at idle
Cause Defective pump control unit
Repair Replacement control unit (Pump removal required)

Fault Fuel Solenoid valve leaking
Cause Road salt attacks the sealant around solenoid.
Repair Replace Solenoid. (No pump removal required)

Fault Lumpy idle usually with grey smoke
Cause Advance Solenoid Failure
Repair Replace advance solenoid. (No pump removal required)

Faults Erratic idle, Engine spontaneous Acceleration                                                    Cause: Boost diaphragm split causing fuel to leak into the inlet manifold.                                                 Cure: Replace boost diaphragm (Pump removal not required)

Fault Starts then cuts out and or runs for 5 minutes then cuts out.
Cause This is due to the pumps drive shaft allowing air to enter the pump (usually after standing overnight).
Repair Replacement of the pumps drive seal is all that is required. (Pump Removal required)

Special note: Do not be tempted to fit a non return valve in this situation as fuel will eventually leak into the engine. 

Fault Power loss, erratic idle.
Cause Pump spring failure
Repair Pump repair (Pump removal required)

Fault Difficult to start and/or starts runs momentarily then cuts out
Cause Fuel draining back to tank once the engine is stopped
Repair Injector return seals, also check the return pipes.

Note: Do not be tempted with a fast fix of using a non return valve, fuel will leak into the engine.