Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 412

move the gauge to the fuel filter input line and re-
test. (Fig. 6).

(6) If the fuel pressure is still below specification,

replace the fuel pump. If the fuel pressure is within
the specification, replace the fuel filter and retest at
the high pressure pump to verify system function.

Fig. 6 FUEL PRESSURE TEST AT FILTER

1 - FUEL SUPPLY FROM FUEL TANK
2 - FUEL FILTER ASSEMBLY

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FUEL SYSTEM

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FUEL DELIVERY

TABLE OF CONTENTS

page

page

FUEL DELIVERY

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . . 6

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

STANDARD PROCEDURE

STANDARD PROCEDURE - DRAINING

FUEL TANK - DIESEL . . . . . . . . . . . . . . . . . . . 8

FUEL CONTAMINATION

. . . . . . . . . . . . . . . . . 8

SPECIFICATIONS

TORQUE

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

SPECIAL TOOLS

FUEL SYSTEM

. . . . . . . . . . . . . . . . . . . . . . . . 9

FUEL DRAIN TUBES

DIAGNOSIS AND TESTING - FUEL SUPPLY

RESTRICTIONS

. . . . . . . . . . . . . . . . . . . . . . . 10

FUEL FILTER

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 10

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 11

FUEL LINES

REMOVAL - HIGH PRESSURE LINES

. . . . . . . . 11

INSTALLATION - HIGH PRESSURE LINES

. . . . 12

FUEL RAIL PRESSURE SENSOR

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 12

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . 12

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 13

FUEL PUMP

DESCRIPTION

DESCRIPTION - HIGH PRESSURE PUMP

. . . 13

DESCRIPTION - LOW PRESSURE PUMP

. . . 13

OPERATION

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . 13

OPERATION - LOW PRESSURE PUMP

. . . . . 16

REMOVAL - HIGH PRESSURE PUMP

. . . . . . . . 17

INSTALLATION - HIGH PRESSURE PUMP

. . . . 17

FUEL PUMP MODULE

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 18

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 20

FUEL QUANTITY CONTROL VALVE

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 21

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . 21

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 21

FUEL RAIL

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 22

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . 22

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 22

FUEL TANK

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 23

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 26

FUEL LEVEL SENDING UNIT / SENSOR

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 28

REMOVAL

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

INSTALLATION

. . . . . . . . . . . . . . . . . . . . . . . . . 29

WATER IN FUEL SENSOR

DESCRIPTION

. . . . . . . . . . . . . . . . . . . . . . . . . 30

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . 30

FUEL DELIVERY

DESCRIPTION

Fuel is collected in the fuel tank. The fuel is drawn

in by the fuel pump module in the tank and distrib-
uted to the fuel filter and onto the high pressure fuel
pump. From there the fuel is distributed onto the
fuel rail and then to the various injectors. Any fuel
not needed flows back to the fuel tank through the
cooler lines and mixes with the cool fuel in the fuel
pump module bowl to be used again (Fig. 1).

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FUEL DELIVERY

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OPERATION

There are several modes of operation for the Com-

mon Rail Diesel Injection System.

Pre-injection The purpose of the pre-injection func-

tion is to reduce noise and pollutants. The coolant
temperature, charge air temperature and atmo-
spheric pressure are use to correct the quantity of
pilot injection. The quantity of pilot injection now
determined is deducted from the quantity of main
injection in order to establish whether sufficient
quantity is available for the following main injection.

The rail pressure is chosen sufficiently high so that

a minimum quantity is injected. If the quantity of
main injection is too small the pilot injection is
switched off by the ECM.

The start of actuation of pilot injection is calcu-

lated dependent on operating point, the following
data being taken into account:

Shutting Off Pre-injection The pre-injection is shut

off when:

• The moment of pre-injection is exceeded

• Engine speed too high

• Pre-injected quantity too low

• Main injected quantity too low

• Insufficient fuel rail pressure

• Engine is switched off
Calculating Pre-injection Quantity The pre-injec-

tion quantity is calculated on the basis of:

• Engine speed

• Atmospheric pressure

• Coolant temperature

• Boost air temperature

• Fuel rail pressure
Main Injection The purpose of main injection func-

tion is to enable the injection time and injection
period calculated by the ECM. The injection quantity
required by the engine is divided into the per-injec-
tion and main injection quantity. If the main injec-
tion quantity computed by the ECM is too small, no
pre-injection takes place.

Start of Actuation

The start of actuation of main injection is depen-

dent on engine speed and quantity. In addition, it is
corrected depending on the following values:

• Coolant temperature

• Boost air temperature

• Atmospheric pressure

• Pre-injection corrected YES/NO

Fig. 1 FUEL SUPPLY

1 - HIGH PRESSURE FUEL PUMP

8 - FUEL INJECTOR

2 - FUEL FROM LOW PRESSURE PUMP

9 - HIGH PRESSURE FUEL FROM HIGH PRESSURE PUMP

3 - FUEL FILTER

10 - FUEL PRESSURE SOLENOID

4 - LOW PRESSURE FUEL PUMP

11- FUEL RAIL

5 - FUEL TANK

12 - FUEL RAIL PRESSURE SENSOR

6 - RETURN FUEL

13 - FUEL QUANTITY CONTROL VALVE

7 - HIGH PRESSURE FUEL FROM HIGH PRESSURE PUMP

14 - FUEL TEMPERATURE VALVE

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FUEL DELIVERY

14 - 7

Switching Off Main Injection

Main injection is switched off when:
• Engine speed is too high >4700 - 4800 rpm

• Main injection quantity too low

• Low fuel pressure in fuel rail

• Engine off

• External quantity control

• Deceleration mode

Calculating Main Injection

The quantity of main injection is calculated by:
• Engine speed

• Atmospheric pressure

• Coolant temperature

• Boost air temperature

• Fuel rail pressure

• Boost pressure

Period of Actuation

For calculating the period of actuation of the main

injection it is necessary to know whether a pre-injec-
tion has occurred or not.

The coolant temperature, charge air temperature

and the atmospheric pressure are used for correcting
the main injection quantity. If main injection quan-
tity is less than a minimum quantity which is depen-
dent on fuel rail pressure, no preinjection takes
place. In this case, only main injection is performed.
If the quantity is then still below the minimum
quantity, neither main injection or pre-injection takes
place (deceleration mode).

Deceleration Mode

The purpose of the deceleration mode is to inter-

rupt the operation of the injectors. The ECM deter-
mines the accelerator pedal position from a supplied
signal and it determines the engine speed by the
crank sensor. In the overrun and with the engine
speed above 1600, with the accelerator pedal no
pressed, the injectors are no longer actuated and the
fuel rail pressure is lowered by the pressure regula-
tor valve.

Full Load Injected Quantity

The purpose of the full load injected quantity is to

minimize the formation of smoke. The ECM limits
the fuel rail pressure when the engine is operating at
full load by way of the quantity control valve, and
quantity of fuel injected by the injectors. this mini-
mizes the formation of smoke when accelerating and
driving at constant speeds. If a fault occurs at the
boost pressure control, full load injected quantity is
reduced.

Limiting Maximum Engine Speed

The ECM determines the engine speed based on

the signal supplied by the crankshaft sensor and lim-

its this by interrupting the operation of the fuel
injectors.

Fuel Quantity Control

The fuel quantity is controlled separately for each

cylinder by the ECM inline with the firing order.The
ECM detects the operating state which exists at the
engine by means of the sensors. In order adapt the
quantity injected, either the fuel rail pressure can be
adjusted by the fuel solenoid and quantity control
valve or the actuation time of the solenoid valves in
the injectors

Boiling Protection

In order to protect against thermal overload and

along with criteria programmed in the ECM, the
injection quantity is reduced as a function of the cool-
ant temperature and vehicle speed. If the coolant
temperature sensor fails the oil temperature signal
from the oil sensor is used as a suitable value.

Fuel Tank Protection

The fuel rail pressure is lowered in order to protect

the fuel tank from overheating. The fuel temperature
sensor measures the temperature of the fuel being
supplied from the tank, in the high pressure flange.
If the fuel is too warm the fuel rail pressure is fur-
ther reduced by the quantity control valve.

STANDARD PROCEDURE

STANDARD PROCEDURE - DRAINING FUEL
TANK - DIESEL

(1) Position a drain hose into the fuel fill opening.
(2) Drain fuel tank using an approved diesel fuel

draining station.

FUEL CONTAMINATION

If a diesel engine’s fuel supply has been contami-

nated with gasoline, the following procedure must be
followed:

(1) Remove all fuel from the fuel tank. (Refer to 14

- FUEL SYSTEM/FUEL DELIVERY - STANDARD
PROCEDURE-DRAINING FUEL TANK) Use an
appropriate fuel container. Dispose of the contami-
nated fuel using the proper procedures.

CAUTION: Dispose of petroleum based products in
a manner consistent with all applicable Local, State,
Federal, and Provincial regulations.

(2) Remove and clean fuel tank. (Refer to 14 -

FUEL SYSTEM/FUEL DELIVERY/FUEL TANK -
REMOVAL)

(3) Install the fuel tank. (Refer to 14 - FUEL SYS-

TEM/FUEL DELIVERY/FUEL TANK - INSTALLA-
TION)

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FUEL DELIVERY

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