Mercedes-Benz Sprinter / Dodge Sprinter. Service manual - part 421

STANDARD PROCEDURE - FUEL PRESSURE
SOLENOID TEST

(1) Disconnect the large fuel rail return hose at

the banjo fitting and clamp it off. Attach a jumper
hose to the banjo fitting and direct the hose into a
test vial. Crank the engine for 10 seconds (Fig. 17).

If return fuel is present in the test vial, replace the

fuel pressure solenoid.

REMOVAL

Review the high pressure fuel system warning before
beginning repair (Refer to 14 - FUEL SYSTEM - WARNING)

WARNING: NO SPARKS, OPEN FLAMES OR SMOK-
ING. RISK OF POISONING FROM INHALING AND
SWALLOWING FUEL. RISK OF INJURY TO EYES
AND SKIN FROM CONTACT WITH FUEL. POUR
FUELS ONLY INTO SUITABLE AND APPROPRI-
ATELY MARKED CONTAINERS. WEAR PROTECTIVE
CLOTHING.

(1) Disconnect negative battery cable.
(2) Remove fuel rail (Refer to 14 - FUEL SYSTEM/

FUEL INJECTION/FUEL INJECTOR - REMOVAL).

(3) Clamp fuel rail securely in vise with protective

jaws.

NOTE: Once removed, the solenoid must always be
replaced.

(4) Counterhold and unscrew the fuel pressure

solenoid and discard the sealing ring (Fig. 18).

INSTALLATION

Review the high pressure fuel system warning before
beginning repair (Refer to 14 - FUEL SYSTEM - WARNING)

CAUTION: There is a special tightening procedure
for the fuel rail solenoid that must be followed
along with the proper use of a torque wrench.
Therefore the fuel rail must be removed before
installing the fuel pressure solenoid. Attention must
be paid to the sealing ring before assembly. If the
sealing ring is damaged when assembling, this
could result in a not so visible leak.

NOTE: Observe the alignment of the pressure sole-
noid. The electrical connection must point in the
same direction as the connection of the injection
line at the fuel rail.

(1) Screw the fuel pressure solenoid with new seal-

ing disc to the fuel rail until hand tight (Fig. 18).

(2) Tighten the fuel rail solenoid as follows :

Fig. 17 CHECKING FUEL RAIL PRESSURE

SOLENOID LEAKAGE

1 - CLAMP RUBBER FUEL RETURN HOSES
2 - ATTACH SEPARATE RUBBER FUEL HOSE
3 - CONTAINER TO MEASURE FUEL LEAKAGE
4 - DISCONNECT RUBBER RETURN HOSE

Fig. 18 FUEL PRESSURE SOLENOID

1 - FUEL PRESSURE SOLENOID
2 - METAL SEALING DISC
3 - FUEL RAIL
4 - VISE

FUEL INJECTION

14 - 41

• Tighten the nut to 60 N·m (44 ft. lbs.)

• Loosen the nut 90 degrees.

• Retighten the nut to 80 N·m (59 ft. lbs.).
(3) Install fuel rail (Refer to 14 - FUEL SYSTEM/

FUEL INJECTION/FUEL INJECTOR - INSTALLA-
TION).

(4) Connect negative battery cable.
(5) Start engine, allow to warm, turn engine off

and inspect for leaks (Refer to 14 - FUEL SYSTEM -
DIAGNOSIS AND TESTING).

FUEL TEMPERATURE SENSOR

DESCRIPTION

The fuel temperature sensor is integrated in the

high pressure fuel pump next to the fuel quantity
valve. The sensor detects the temperature of the fuel
and supplies that information to the ECM. The sen-
sor ranges from - 40°F (- 40C) to 284°F (140°C). If
the engine is cold, the actual value sent will read
ambient temperature. The value rises after the
engine has been started.

OPERATION

An negative temperature coefficient (NTC) resistor

integrated in the fuel temperature sensor alters it’s
electrical resistance in line with the fuel temperature
(the resistance drops as the temperature rises). The
ECM uses this reading to calculate optimum engine
performance under all driving conditions. If the fuel
is to warm, the rail pressure in the system is low-
ered. The controller quantity of the pressure regulat-
ing valve is reduced and the fuel temperature is
lowered.

REMOVAL

NOTE: Capture and properly store all fluid seepage
in appropriately marked containers.

(1) Disconnect the negative battery cable.
(2) Remove the fuel temperature sensor from the

high pressure pump (Fig. 19).

INSTALLATION

(1) Clean sealing surfaces.
(2) Install new seal on sensor.
(3) Screw the sensor into the high pressure pump

and tighten to 18 lbs.ft. (25 N·m) (Fig. 19)

(4) Connect negative battery cable.
(5) Start engine, allow to warm, shut engine off

and inspect for leaks (Refer to 14 - FUEL SYSTEM/
FUEL INJECTION - WARNING).

INTAKE AIR TEMPERATURE
SENSOR

DESCRIPTION

The intake air temperature sensor is located

between the charge air pipe and the charge air dis-
tribution of the cylinders. The intake air temperature
sensor measures the temperature of the air as it is
supplied to the cylinders and transmits the value to
the ECM. This is required in order to determine the
density of the air being supplied for the combustion
process. The value range is from minus 40°F up to
302°F (minus 40°C to 150°C).

Fig. 19 HIGH PRESSURE FUEL PUMP

1 - HIGH PRESSURE PUMP
2 - FUEL SUPPY TO FUEL RAIL
3 - FUEL SUPPLY LINE
4 - FUEL RETURN LINE
5 - FUEL TEMPERATURE SENSOR
6 - FUEL QUANTITY CONTROL VALVE
7 - OIL LEVEL INDICATOR
8 - VACUUM PUMP

14 - 42

FUEL INJECTION

OPERATION

The

Negative

Temperature

Coefficient

(NTC)

resister located within the intake air temperature
sensor alters it’s resistance in line with the charge
air temperature. If the engine is cold, the value
equals ambient temperature. For a temperature of
68°F (20°C) the resistance is approximately 6000
ohms. For a temperature of 104°F (40°C) the resis-
tance is approximately 3300 ohms (Fig. 20).

REMOVAL

(1) Disconnect the negative battery cable.
(2) Unplug the wiring harness connector at the

intake air temperature sensor.

(3) Press together the sensor locking arms and

remove the sensor from the charge air pipe (Fig.
21).

INSTALLATION

(1) Position the intake air temperature sensor

above the charge air pipe access hole.

(2) Press together the sensor locking tabs, seat the

sensor to the pipe and release tabs (Fig. 21).

(3) Connect negative battery cable.

INTAKE AIR PRESSURE SEN-
SOR

DESCRIPTION

An absolute pressure sensor is mounted to the air

cleaner housing. The sensor is used by the ECM to
adjust for changes in altitude and for air intake
obstructions due to a clogging air cleaner.

OPERATION

The ECM uses the intake air pressure sensor to

monitor the intake pressure. Monitoring this pres-
sure allows better control of the variable geometry
turbocharger to suit the driving environment and
preserve turbocharger durability.

REMOVAL

(1) Disconnect the negative battery cable.
(2) Disconnect the sensor electrical connector.
(3) Remove the air intake pressure sensor.

Fig. 20 INLET AIR TEMPERATURE SENSOR

1 - INTAKE AIR TEMPERATURE SENSOR
2 - PIPE

Fig. 21 BOOST PRESSURE AND INLET AIR

TEMPERATURE SENSORS

1 - CHARGE AIR DUCT
2 - INTAKE AIR TEMPERATURE SENSOR
3 - BOOST PRESSURE SENSOR

FUEL INJECTION

14 - 43

INSTALLATION

(1) Positon the pressure sensor in the air cleaner

cover and install the fasteners (Fig. 22).

(2) Connect the electrical connector (Fig. 22).
(3) Connect the negative battery cable.

MANIFOLD AIR FLOW (MAF)
SENSOR

DESCRIPTION

The Mass Air Flow (MAF) Sensor is located in the

air intake port between the air filter and the turbo-
charger (Fig. 23). The MAF sensor uses semiconduc-
tor technology throughout, and is used to calculate
the air mass flowing past it per time unit. This mass
is important for determining the exhaust gas recircu-
lation rate. The MAF sensor sends a corresponding
signal to the ECM, which evaluates the signal to
adjust the exhaust gas recirculation valve.

OPERATION

The ECM uses the mass air flow (MAF) sensor to

measure air density. The temperature resistor located
at the front of the MAF sensor measures the temper-
ature of the inlet air. By varying the voltage, the
electronic circuit regulates the temperature of the
heating resistor in the rear so that it is 320° F
(160°C) higher than the temperature of the intake
air. The temperature at the heating resistor is mea-
sured by a sensor resistor in-between.

Because the incoming air has a cooling effect, the

greater the amount of air that flows in, then the
higher the voltage of the heating resistor. The heat-
ing resistor is therefore a measure of mass of air
flowing past. If a temperature change occurs as a
result of a increase or reduction of air flow, the ECM
corrects the voltage at the heating resistor until the
temperature difference is again achieved. This con-
trol voltage is use by the ECM as a unit measure for
metered air mass.

REMOVAL

(1) Disconnect the negative battery cable.
(2) Detach the air hose at the Manifold Air Flow

(MAF) sensor

(3) Unplug the MAF wiring harness connector.
(4) Remove the screws retaining the MAF sensor

to the air cleaner housing, and remove MAF sen-
sor.

Fig. 22 AIR CLEANER HOUSING

1 - AIR FLOW SENSOR
2 - GASKET
3 - AIR INTAKE HOSE
4 - AIR CLEANER HOUSING
5 - AIR CLEANER ELEMENT
6 - AIR INTAKE PRESSURE SENSOR
7 - AIR CLEANER HOUSING COVER

Fig. 23 MASS AIR FLOW (MAF) SENSOR

14 - 44

FUEL INJECTION

Content .. 419 420 421 422 ..