Check low-pressure fuel circuit

AR07.15-B-2000DD

Check low-pressure fuel circuit

03.02.2020

Engine

906.999

Engine

924.92

Engine

926.942 in model 382.171/176

Engine

926.95

Diagram of the fuel circuit shown on the 904 engine

1

Fuel supply pump

B10

Fuel temperature probeFuel circuit

1.2

Fuel supply pump check valve

A

Fuel supply (suction line)

2

Fuel filter

B

Fuel return (recovery fuel)

2.1

Fuel filter return valve

C

Fuel flow (pressure line after the fuel supply pump and the fuel filter)

2.2

Permanent trap on the fuel filter

D

High pressure fuel line (MR/PLD injection unit outlet)

3

Fuel pre-filter

E

Fuel return (fuel filter drain)

3.1

Fuel pre-filter check valve

- - -

Fuel channels on the engine block

4

Check valve in the fuel flow line (forced opening)

___

Fuel lines

5

Check valve in the fuel return line (forced opening)

G

Pressure check

6

MR/PLD injector units

H

Fuel return flow check

7

Permanent restriction

I

Fuel pressure after fuel filter Idle speed:  4.3 bar Limit speed range: 4.0 to 6.5 bar

7.03

Relief valve

II

Fuel return flow in the combined injector holdersTime check: 5 minIdle speed: damped by Diesel oilLimit speed regime: only drops, maximum

8

Fuel supply channel bypass to the return channel

III

Fuel return flow after the fuel filter return valveIdle speed and flow limitation regime:  0.3 l /minFuel return flow at the relief valve Idle speed: 0.9 to 1.7 l/minLimit speed range: 2.7 to 7.5 l/min

9

Nozzle holder combined with injection nozzle

IV

Suction pressure before the fuel pumpIdle speed: -0.09 to -0.12 bar Limit speed regime: -0.4 to -0.5 bar

10

Fuel tank

V

Low pressure fuel circuit tightnessPressure check: 10 barCheck time: 5 minPressure drop:  0.25 bar

30.03

Fuel supply pump pressure limiting valve

Diagram of the fuel circuit shown on the 906 engine

1

Fuel supply pump

2

Fuel filter

3

Fuel pre-filter

4.1

Check valve in the fuel flow line

5.1

Check valve in the fuel return line (to the reservoir)

6

MR/PLD injector units

7.03

Relief valve

9

Nozzle holder combined with injection nozzle

11

Fuel returning channel

12

Fuel returning pipe

13

Fuel line (fuel pre-filter to the fuel supply pump)

14

Fuel supply channel

15

Nozzle fuel returning channel

16

Pressure tube connection

17

Injection pipe

A

Fuel supply (suction line)

B

Fuel return (recovery fuel)

C

Fuel flow (pressure line after the fuel supply pump and the fuel filter)

D

High pressure fuel line (MR/PLD injection unit outlet)

E

Fuel return (fuel filter drain)

 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

1

Start the engine and warm it up to operating temperature

 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

2

Let engine running in limit speed

 Approximately 2 to 3 minutes.

3

Stop the engine

Remove/install

4

Remove air inlet tube (air filter turbocharger)

5

Carry out visual checks on all fuel pipes, threaded connections and components

 Replace leaking or damaged parts, if necessary retighten threaded connections.

6

Clean the fuel prefilter filtering element (3)



.

AP47.20-B-0730DD

7

Replace the fuel filter (2)



.

AP47.20-B-0780XA



Check

8

Open the fuel tank cap

 To relief the pressure of the fuel system.

9

Test the fuel pressure in the circuit after the fuel filter (2)

.

AR07.15-B-2000-01DA



Fuel pressure downstream of fuel filter, MR (PLD) hydraulic components check

.

AD07.15-B-7001-01D

 High-pressure hose

*123589042118

 Adaptation parts

*541589009100

 Tester

*541589022100

10

Check fuel return flow volume on the combined injector holder assemblies (9)

.

AR07.15-B-2000-01DD



.

AD07.15-B-7001-07D

 .Injection pipe of the injection unit to the injector's pressure tube

*BA07.15-B-1004-01A

 Fuel tubes in the cylinder head

*BA07.15-B-1006-01A

 Ring wrench

*000589070300

 Box wrench bit

*000589680300

 Adaptation parts

*541589009100

 Retainer wrench

*904589010700

11

Measure fuel return flow amount in the engine

.

AR07.15-B-2000-01DC



.

AD07.15-B-7001-06D

 Fuel tubes in the solenoid valve

*BA07.15-B-1007-01A

 Connectors

*405589009100

 Adaptation parts

*541589009100

12

Test fuel suction pressure on the fuel supply pump (1)

.

AR07.15-B-2000-01DB



.

AD07.15-B-7001-03D

 Connectors

*405589009100

 Adaptation parts

*541589009100

 Tester

*617589042100

13

Check the low pressure fuel circuit in the engine for leakage

.

AR07.15-B-2000-01DE



.

AD07.15-B-7001-08D

 High-pressure hose

*123589042118

 Adaptation parts

*541589009100

 Tester

*541589022100

14

Install in reverse order

15

Bleed the fuel system

 Use the starter to run the engine for a maximum of 90 seconds, then repeat the start procedure after a pause of at least 2 minutes. The fuel system bleeds automatically.

16

Test vehicle power on a dynamometer

 If no improvement in fuel consumption or performance has been achieved, connect a fuel consumption measurement system. Diesel injection system with injection unit (MR/PLD)

 Diesel injection system with injection unit (MR/PLD)

Number

Designation

Engine 904.9, 906.9, 924.9, 926.9

BA07.15-B-1004-01A

Injection pipe of the injection unit to the injector's pressure tube

Only for the tube A 906 070 14 33

1st stage

Nm

10

2nd stage

angular

80°

Only for the tube A 906 070 24 33

1st stage

Nm

15

2nd stage

angular

90°

 Diesel injection system with injection unit (MR/PLD)

Number

Designation

Engine 904.9, 906.9, 924.9, 926.9

BA07.15-B-1006-01A

Fuel tubes in the cylinder head

Nm

50

 Diesel injection system with injection unit (MR/PLD)

Number

Designation

Engine 904.9, 906.9, 924.9, 926.9

BA07.15-B-1007-01A

Fuel tubes in the solenoid valve

Nm

50