DAF LF45, LF55 Series. Manual - part 283

©

 200416

2-1

Fuel system

DIAGNOSTICS

ΛΦ45/55 series

4

1

2. FUEL SYSTEM

2.1 INTRODUCTION

If there is a fault in the system, it is usually 

detected by the electronic unit in the form of a 

fault code. This fault code can be read out using 

DAVIE. The fault-finding table contains possible 

causes of symptoms not detected by the 

electronic unit. 

DIAGNOSTICS

2-2

©

 200416

Fuel system

1

ΛΦ45/55 series

4

2.2 FAULT-FINDING TABLE

SYMPTOM: ENGINE CAN BE STARTED, BUT DOES NOT RUN

Possible cause

Remedy

Poor fuel quality

Drain fuel, flush fuel system, replace the fuel filters 

and fill fuel tank with fuel

Air in fuel system

Check for drawing in of air:

-

via the suction pipe

Fuel fine filter/coarse filter clogged

Replace fuel fine filter and clean the system

No fuel supply/high-pressure pump or fuel lift pump 

defective; no delivery

Check:

-

the fuel level

-

the rail pressure

-

the pipes for blockage and leaks

-

the fuel lift pump

-

the high-pressure pump

SYMPTOM: ENGINE STALLS AND RUNS AGAIN AFTER RE-STARTING

Possible cause

Remedy

Air in fuel system

Check for drawing in of air:

-

via the suction pipe

SYMPTOM: ENGINE STARTS POORLY

Possible cause

Remedy

Poor fuel quality

Drain fuel, flush fuel system, replace the fuel filters 

and fill fuel tank with fuel

Air in fuel system

Check for drawing in of air:

-

via the suction pipe

Fuel fine filter/coarse filter clogged

Replace fuel fine filter and clean the system

Injector(s) mechanically defective or clogged

Replace the injectors

High-pressure pump or fuel lift pump delivery too 

low

Check:

-

the high-pressure pump

-

the fuel lift pump

Internal fuel leak between fuel supply pipe(s) and 

injector(s)

Check the quantity of return fuel

SYMPTOM: ENGINE RUNS AT (INCREASED) IDLING SPEED AND DOES NOT RESPOND TO AC-

CELERATOR PEDAL

Possible cause

Remedy

Mechanical defect of accelerator pedal sensor

Check:

-

mechanical connection of sensor/accelerator 

pedal

-

accelerator pedal sensor

©

 200416

2-3

Fuel system

DIAGNOSTICS

ΛΦ45/55 series

4

1

SYMPTOM: DIESEL KNOCK DURING ACCELERATION

Possible cause

Remedy

Poor fuel quality

Drain fuel, flush fuel system, replace the fuel filters 

and fill fuel tank with fuel

Air in fuel system

Check for drawing in of air:

-

via the suction pipe

Injector defective

Check the injectors

SYMPTOM: IRREGULAR RUNNING OF ENGINE

Possible cause

Remedy

Poor fuel quality

Drain fuel, flush fuel system, replace the fuel filters 

and fill fuel tank with fuel

Air in fuel system

Check for drawing in of air:

-

via the suction pipe

Fuel fine filter/coarse filter clogged

Replace fuel fine filter and clean the system

Injector(s) mechanically defective or clogged

Replace the injectors

Injector defective

Check the injectors

High-pressure pump or fuel lift pump delivery too 

low

Check: 

-

the high-pressure pump

-

the fuel lift pump

SYMPTOM: REDUCED POWER AT ALL ENGINE SPEEDS

Possible cause

Remedy

Poor fuel quality

Drain fuel, flush fuel system, replace the fuel filters 

and fill fuel tank with fuel

Fuel fine filter/coarse filter clogged

Replace fuel fine filter and clean the system

Injector(s) mechanically defective or clogged

Replace the injectors

Mechanical defect of accelerator pedal sensor

Check:

-

mechanical connection of sensor/accelerator 

pedal

-

accelerator pedal sensor

High-pressure pump or fuel lift pump delivery too 

low

Check:

-

the high-pressure pump

-

the fuel lift pump

SYMPTOM: REDUCED POWER ABOVE A CERTAIN ENGINE SPEED

Possible cause

Remedy

Fuel fine filter/coarse filter partially clogged

Replace fuel fine filter and clean the system

Injector(s) mechanically defective or clogged

Replace the injectors

Air leak in inlet system

Pressure-test the inlet system

DIAGNOSTICS

2-4

©

 200416

Fuel system

1

ΛΦ45/55 series

4

High-pressure pump or fuel lift pump delivery too 

low

Check:

-

the high-pressure pump

-

the fuel lift pump

Fault in electrical components/wiring of:

-

connectors

Check the electrical system

SYMPTOM: REDUCED POWER ABOVE A CERTAIN ENGINE SPEED

Possible cause

Remedy

SYMPTOM: ENGINE SLUGGISH WHEN ACCELERATING OR UNDER HIGH LOAD

Possible cause

Remedy

Internal fuel leak between fuel supply pipe(s) and 

injector(s)

Check the quantity of return fuel

High-pressure pump or fuel lift pump delivery too 

low

Check:

-

the high-pressure pump

-

the fuel lift pump

SYMPTOM: WHITE/BLUE SMOKE IS EMITTED

Possible cause

Remedy

Poor fuel quality

Drain fuel, flush fuel system, replace the fuel filters 

and fill fuel tank with fuel

Air in fuel system

Check for drawing in of air:

-

via the suction pipe

Fuel fine filter/coarse filter clogged

Replace fuel fine filter and clean the system

Injector(s) mechanically defective or clogged

Replace the injectors

High-pressure pump or fuel lift pump delivery too 

low

Check:

-

the high-pressure pump

-

the fuel lift pump

Fault in electrical components/wiring of:

-

connectors

Check the electrical system

SYMPTOM: BLACK SMOKE IS EMITTED

Possible cause

Remedy

Injector(s) mechanically defective or clogged

Replace the injectors

SYMPTOM: ENGINE OVERHEATED

Possible cause

Remedy

Poor fuel quality

Drain fuel, flush fuel system, replace the fuel filters 

and fill fuel tank with fuel