Check low-pressure fuel circuit

AR07.15-W-2000J

Check low-pressure fuel circuit

27.08.2020

Engine

900.9 in model 375.1, 970, 972, 975, 976

Engine

902.9 in model 375.1, 970, 972, 974, 975, 976

Engine

902.9 in model 375.3, 950.5/6, 952.5/6, 953.6, 954.5

Engine

902.9 in model 957

except code MS8 (Natural gas engine)

Engine

924.9 in model 958.0, 970, 972, 974, 975, 976

Engine

925.9 in model 970, 972, 974

Engine

926.9 in model 950.5/6, 952.5/6, 953.6, 954.5, 957, 958.2

Engine

926.9 in model 958.0

 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

 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

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-1000-02F



Check

1

Open maintenance flap

Model 957 only

2

Tilt cab

3

Remove soundproofing on frame at the left

4

Visually check all fuel lines, fittings, screwed connections and components of the fuel system

If damaged or leaky:



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

5

Clean fouled components of the fuel system on the outside

6

Open cap on fuel tank

7

Drain fuel prefilter with heated water separator and check fuel prefilter insert for contamination

With code K81(Fuel preheater with water separator)

If there is severe contamination:



Replace fuel prefilter element.



Model 375, 950, 952, 953, 954, 957, 970, 972, 974, 975, 976

AP47.20-W-0783A

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

8

Check fuel pre-filter insert for soiling and clean if necessary



Model 375, 950, 952, 953, 954, 957, 970, 972, 974, 975, 976

AP47.20-W-0730B

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

If there is severe contamination:



Replace fuel prefilter element.

9

Check fuel filter element for soiling

If there is severe contamination:



Replace fuel filter.



Model 375, 950, 952, 953, 954, 957, 970, 972, 974, 975, 976

AP47.20-W-0780B

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

10

Start engine and bring to operating temperature

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

11

Switch off ignition

12

Check fuel low-pressure circuit for leaktightness

Only if the engine starts badly.

AR07.15-W-2000-04J

Pressure drop in low-pressure fuel circuit

*BE47.00-N-1003-01B

 Banjo bolt, fuel line (flame starting system) to banjo bolt and valve

*BA47.25-N-1006-01J

 Nut, feed line and return line to fuel filter

*BA47.25-N-1008-01J

 High-pressure hose

*123589042118

 Tester

*541589022100

 Adaptation parts

*541589009100

13

Measure fuel pressure downstream of fuel filter

Only for vehicles with poor engine performance.

AR07.15-W-2000-02J

 If the fuel pressure falls within the tolerance range, no further checks need to be carried out on the low pressure fuel circuit.

Fuel pressure downstream of fuel filter

*BE47.00-N-1001-01B

 Banjo bolt, fuel line (flame starting system) to banjo bolt and valve

*BA47.25-N-1006-01J

 High-pressure hose

*123589042118

 Adaptation parts

*541589009100

 Tester

*541589022100

If the fuel pressure is too high:



Measure fuel return quantity at the fuel tank.

AR07.15-W-2000-03J

Fuel return quantity at fuel tank

*BE47.00-N-1002-01B

If the fuel pressure is too low:



Measure fuel intake pressure upstream of fuel pump.

AR07.15-W-2000-05J

Fuel suction pressure upstream of fuel pump at filter supply

*BE47.00-N-1004-01B

 Nut, feed line and return line to fuel filter

*BA47.25-N-1008-01J

 Tester

*617589042100

 Adaptation parts

*541589009100

14

Close fuel tank cap

15

Start the engine and bleed the fuel system

 The fuel system is bled automatically.

16

Install soundproofing on frame at the left

17

Tilt back cab

18

Close maintenance flap

Model 957 only

Check values for fuel pressure

Number

Designation

Engine 900.9, 904.9, 924.9, 925.9, 926.9, engine 902.9, 906.9 except natural gas engine

BE47.00-N-1001-01B

Fuel pressure downstream of fuel filter

Idling speed

bar

4,3

Breakaway speed

bar

4,0...6,5

Check values for fuel pressure

Number

Designation

Engine 900.9, 904.9, 924.9, 925.9, 926.9, engine 902.9, 906.9 except natural gas engine

BE47.00-N-1002-01B

Fuel return quantity at fuel tank

Idling speed

l/min

0,9...2,0

Breakaway speed

l/min

2,0...10,5

Check values for fuel pressure

Number

Designation

Engine 900.9, 904.9, 924.9, 925.9, 926.9, engine 902.9, 906.9 except natural gas engine

BE47.00-N-1003-01B

Pressure drop in low-pressure fuel circuit

bar

0

Check values for fuel pressure

Number

Designation

Engine 900.9, 904.9, 924.9, 925.9, 926.9, engine 902.9, 906.9 except natural gas engine

BE47.00-N-1004-01B

Fuel suction pressure upstream of fuel pump at filter supply

Breakaway speed

bar

­0,4...­0,5

 Fuel lines/hoses

Number

Designation

Engine 900.9, 904.9, 924.9, 925.9, 926.9, engine 902.9, 906.9 except natural gas engine

BA47.25-N-1006-01J

Banjo bolt, fuel line (flame starting system) to banjo bolt and valve

Nm

15

 Fuel lines/hoses

Number

Designation

Engine 900.9, 904.9, 924.9, 925.9, 926.9, engine 902.9, 906.9 except natural gas engine

BA47.25-N-1008-01J

Nut, feed line and return line to fuel filter

Nm

45