Check low-pressure fuel circuit

AR07.15-W-2000C

Check low-pressure fuel circuit

27.08.2020

Engine

457.9 in model 374, 375, 940, 942, 943, 944, 958

 Warning

Risk of injury caused by body parts being pinched or crushed as cab is tilted

Ensure that no one is within the tilting range of the cab as it is being tilted. Always tilt the cab all the way to the end position and secure it with the safety strut.

AS60.80-Z-0001-01A

 Warning

Risk of accident from vehicle starting off by itself when engine running. Risk of injury (bruises and burns) resulting from working on the engine while it is being started or when it is running.

Secure vehicle to prevent it from starting off by itself. Wear closed and snug-fitting work clothes. Do not touch hot or rotating parts.

AS00.00-Z-0005-01A

 Danger

Risk of explosion caused by fuel igniting, risk of poisoning caused by inhaling and swallowing fuel as well as risk of injury to eyes and skin caused by contactwith fuel.

No fires, sparks, open flames or smoking. Pour fuels into suitable and appropriately marked containers only.
Wear protective clothing when handling fuel.

AS47.00-Z-0001-01A

Topical note

Notes on tilting the cab

AH60.80-N-0003-01A

Notes on possible sources of fault in the low-pressure fuel circuit

AH07.15-N-1000-02C



Check

1

Tilt cab

2

Remove soundproofing on left

3

Carry out a visual inspection of all fuel lines, connections, threaded connections and components for fuel system

 Clean and dry components in case of contamination. Allow engine to run at maximum governed rpm for approx. 2 to 3 min.

If damaged or leaky:



Replace any assembly part as necessary, seal connection and tighten threaded connection using the prescribed tightening torque.

4

Open cap on fuel tank

5

Drain fuel prefilter, and check fuel prefilter element and replace if necessary

Only for vehicles with code K81 (Fuel prefilter with heated water separator).

6

Check fuel filter element

 Collect escaping fuel.

If there is severe contamination:



Replace fuel filter element.



MODEL 374, 375, 940, 942, 943, 944

AP47.20-W-0780A

 Model 958
No instructions were created yet for these variants.

7

Start engine and bring to operating temperature

 The fuel temperature in the fuel tank must be  40°C.

8

Switch off ignition

9

Check low-pressure fuel circuit for signs of leaktightness

Only if the engine starts badly.

AR07.15-W-2000-04C

Pressure drop in low pressure fuel circuit

*BE47.00-N-1003-01D

 Banjo bolt, fuel line to fuel filter housing

*BA47.25-N-1004-01M

 Banjo bolt, fuel line to fuel heat exchanger

*BA47.25-N-1009-01M

 Banjo bolt, fuel line to solenoid valve of flame starting system/ banjo bolt for fuel filter housing

*BA47.25-N-1017-01M

 High-pressure hose

*123589042118

 Tester

*541589022100

 Adaptation parts

*541589009100

10

Measure fuel pressure downstream of fuel filter

Only for vehicles with poor engine performance.

AR07.15-W-2000-02C

 If fuel pressure is in the tolerance range, do not carry out any further checks at the low-pressure fuel circuit.

Fuel pressure downstream of fuel filter

*BE47.00-N-1001-01D

 Banjo bolt, fuel line to fuel filter housing

*BA47.25-N-1004-01M

 Banjo bolt, fuel line to solenoid valve of flame starting system/ banjo bolt for fuel filter housing

*BA47.25-N-1017-01M

 High-pressure hose

*123589042118

 Tester

*541589022100

 Adaptation parts

*541589009100

If fuel pressure after measurement is too high:



Measure fuel return quantity at the fuel tank.

AR07.15-W-2000-03C

Fuel return quantity at fuel tank

*BE47.00-N-1002-01D

If fuel pressure after measurement is too low:



Measure fuel intake pressure upstream of fuel pump.

AR07.15-W-2000-05C

Fuel intake pressure upstream of fuel pump

*BE47.00-N-1004-01D

 Banjo bolt, fuel line to fuel heat exchanger

*BA47.25-N-1009-01M

 Tester

*617589042100

 Clamp

*000589403700

 Adaptation parts

*541589009100

11

Close fuel tank cap

12

Start the engine and bleed the fuel system

 The fuel system is bled automatically. Run the engine for approx. 1 minute.

If engine fails to start or only runs for a brief period:



Bleed fuel system manually.

AR47.00-W-1720C

13

Install soundproofing on left

14

Tilt back cab

Fuel circuit check values

Number

Designation

ENGINE 457.9

BE47.00-N-1001-01D

Fuel pressure downstream of fuel filter

Idling speed

bar

1,8...2,8

Breakaway speed

bar

6,2...7,2

Fuel circuit check values

Number

Designation

ENGINE 457.9

BE47.00-N-1002-01D

Fuel return quantity at fuel tank

Idling speed

l/min

1,1...1,5

Breakaway speed

l/min

2,2...2,8

Fuel circuit check values

Number

Designation

ENGINE 457.9

BE47.00-N-1003-01D

Pressure drop in low pressure fuel circuit

Test pressure 5.0 bar / test period 5 min.

bar

0

Fuel circuit check values

Number

Designation

ENGINE 457.9

BE47.00-N-1004-01D

Fuel intake pressure upstream of fuel pump

Breakaway speed

bar

–0,30...–0,15

 Fuel lines/hoses

Number

Designation

ENGINE 457.9

BA47.25-N-1004-01M

Banjo bolt, fuel line to fuel filter housing

Nm

50

 Fuel lines/hoses

Number

Designation

ENGINE 457.9

BA47.25-N-1009-01M

Banjo bolt, fuel line to fuel heat exchanger

Nm

50

 Fuel lines/hoses

Number

Designation

ENGINE 457.9

BA47.25-N-1017-01M

Banjo bolt, fuel line to solenoid valve of flame starting system/ banjo bolt for fuel filter housing

Nm

15