engine MERCEDES-BENZ ML320 1997 Complete Service Manual

160 Catalytic converter
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Catalytic converter
Your Mercedes-Benz is equipped with monolithic type
catalytic converters, an important element in
conjunction with the oxygen sensors to achieve
substantial control of the pollutants in the exhaust
emissions. Keep your vehicle in proper operating
condition by following our recommended maintenance
instructions as outlined in your Service Booklet.Caution!
To prevent damage to the catalytic converters, use only
premium unleaded gasoline in this vehicle.
Any noticeable irregularities in engine operation should
be repaired promptly. Otherwise, excessive unburned
fuel may reach the catalytic converter causing it to
overheat, which could start a fire.
Wa r n i n g !
As with any vehicle, do not idle, park or operate
this vehicle in areas where combustible materials
such as grass, hay or leaves can come into contact
with the hot exhaust system, as these materials
could be ignited and cause a vehicle fire.

161 Emission control
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cluster displayPractical hints Car care Index Emission control
Certain systems of the engine serve to keep the toxic
components of the exhaust gases within permissible
limits required by law.
These systems, of course, will function properly only
when maintained strictly according to factory
specifications. Any adjustments on the engine should,
therefore, be carried out only by authorized Mercedes-
Benz Light Truck Center qualified technicians. Engine
adjustments should not be altered in any way. Moreover,
the specified service jobs must be carried out regularly
according to Mercedes-Benz servicing requirements.
For details refer to the Service Booklet.
Wa r n i n g !
Inhalation of exhaust gas is hazardous to your
health. All exhaust gas contains carbon monoxide,
and inhaling it can cause unconsciousness and
lead to death.Do not run the engine in confined areas (such as a
garage) which are not properly ventilated. If you
think that exhaust gas fumes are entering the
vehicle while driving, have the cause determined
and corrected immediately. If you must drive under
these conditions, drive only with at least one
window fully open.

162 Steering lock
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Steering lock
0The key can be withdrawn in this position only. The
steering is locked when the key is removed from the
steering lock. If necessary, move steering wheel
slightly to allow the locking mechanism to engage.
The key can only be removed with the selector lever
in position “P”. After removing the key or with the
key in steering lock position 0, the selector lever is
locked in position “P”.1Steering is unlocked.
(If necessary, move steering wheel slightly to allow
the key to be turned clockwise to position 1.) Most
electrical consumers can be operated. For detailed
information see respective subjects.
2Driving position.
3Starting position.
See page 164 for starting and turning off the engine.
Wa r n i n g !
When leaving the vehicle always remove the key
from the steering lock, and lock the vehicle. Do not
leave children unattended in the vehicle, or with
access to an unlocked vehicle. Unsupervised use of
vehicle equipment may cause serious personal
injury.

163 Steering lock
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cluster displayPractical hints Car care Index Caution!
To prevent accelerated battery discharge and a possible
dead battery, always remove the key from the steering
lock. Do not leave the key in steering lock position 0.
Notes:
A warning sounds when the driver’s door is opened
while the key is in steering lock position 1 or 0.
With the engine at idle speed, the charging rate of the
alternator (output) is limited.It is therefore recommended that you turn off
unnecessary electrical consumers while driving in stop-
and-go traffic. This precaution helps to avoid draining of
the battery.
Unnecessary strain on the battery and charging system
may be minimized by turning off the following power
consumers, for example: Heated seats, rear window
defroster.

164 Starting and turning off the engine
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Starting and turning off the engine
Before starting
Ensure that parking brake is engaged and that selector
lever is in position “P” or “N”. Turn key in steering lock
to position 2. The charge indicator lamp should come on.
Starting
Do not depress accelerator.
Briefly turn key in steering lock clockwise to the stop
and release. The starter will engage until the engine is
running.
If engine will not run, and the starting procedure stops,
turn key completely to the left and repeat starting the
engine.
After several unsuccessful attempts, have the system
checked at the nearest authorized Mercedes-Benz Light
Truck Center.
A starting procedure can be interrupted by turning the
key to steering lock position 0.Important!
Due to the installed starter non-repeat feature, the key
must be turned completely to the left before attempting
to start the engine again.
In areas where temperatures frequently drop below -4°F
(-20°C) we recommend that an engine block heater be
installed. Your authorized Mercedes-Benz Light Truck
Center will advise you on this subject.
Note:
In case the engine cannot be started and the
messagesÁ and î are shown in the odometer
display field, the system is not operational. Contact an
authorized Mercedes-Benz Light Truck Center or call
1-800-FOR-MERCedes (in the USA), or 1-800-387-0100
(in Canada).
Turning off
Turn the key in the steering lock to position 0 to stop the
engine.
The key can only be removed with the selector lever in
position “P”.

165 Automatic transmission
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cluster displayPractical hints Car care Index Automatic transmissionThe automatic transmission selects individual gears
automatically, dependent upon
•Selector lever position
•Accelerator position
•Vehicle speed
The gear shifting process is continuously adapted,
dependent on the driving style, the driving situation
and the road characteristics.
Important!
When parking the vehicle or before working on the
vehicle with the engine running, firmly depress the
parking brake pedal and shift the selector lever into “P”.

166 Automatic transmission
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Driving
The selector lever is automatically locked while in
position “P”. To move the selector lever out of
position “P”, the service brake pedal must be firmly
depressed before the shift lock will release.
Shift selector lever to the desired position only when the
engine is idling normally and the service brake is
applied. Do not release the brake until ready to drive.
The vehicle may otherwise start creeping when the
selector lever is in drive or reverse position.Important!
After selecting any driving position from “N” or “P”,
wait a moment to allow the gear to fully engage before
accelerating, especially when the engine is cold.
Accelerator position
Partial throttle = early upshifting = normal acceleration
Full throttle = later upshifting = rapid acceleration
Kickdown (depressing the accelerator beyond full
throttle) = downshifting to a lower gear = maximum
acceleration. Once the desired speed is attained, ease up
on the accelerator – the transmission shifts up again.
Stopping
For brief stops, e.g. at traffic lights, leave the
transmission in gear and hold vehicle with the service
brake.
For longer stops with the engine idling, shift into “N”
or “P” and hold the vehicle with the service brake.
When stopping the vehicle on an uphill gradient, do not
hold it with the accelerator, use the brake. This avoids
unnecessary transmission heat build up.
Wa r n i n g !
It is dangerous to shift the selector lever out of “P”
or “N” if the engine speed is higher than idle speed.
If your foot is not firmly on the brake pedal, the
vehicle could accelerate quickly forward or in
reverse. You could lose control of the vehicle and
hit someone or something. Only shift into gear
when the engine is idling normally and when your
right foot is firmly on the brake pedal.

167 Automatic transmission
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data Instruments
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cluster displayPractical hints Car care Index Maneuvering
To maneuver in tight areas, e.g. when pulling into a
parking space, control the vehicle speed by gradually
releasing the brakes. Accelerate gently and never
abruptly step on the accelerator.
To rock a vehicle out of soft ground (mud or snow),
alternately shift from forward to reverse, while applying
slight partial throttle.
Rocking a vehicle free in this manner may cause the
ABS or traction system malfunction indicator lamp to
come on. Turn off and restart the engine to clear the
malfunction indication.Towing a trailer
If the transmission hunts between gears on inclines,
manually shift to a lower gear (select “4”, “3”, “2”
or “1”). A lower gear and reduction of speed reduces the
chance of engine overloading and / or overheating.
At very steep inclines, not manageable with selector
lever in position “1”, switch transfer case to LOW
RANGE, see page 209 for instructions on how to engage
LOW RANGE.
For instructions on trailer towing refer to page 190.
Wa r n i n g !
Getting out of your vehicle with the selector lever
not fully engaged in position “P” is dangerous.
Also, when parked on an incline, position “P” alone
may not prevent your vehicle from moving,
possibly hitting people or objects.Always set the parking brake in addition to shifting
to position “P”, see page 173 for parking brake. When parked on an incline, also turn front wheel
against curb.
Wa r n i n g !
When leaving the vehicle always remove the key
from the steering lock, and lock the vehicle. Do not
leave children unattended in the vehicle, or with
access to an unlocked vehicle. Children could move
the gear selector lever from position “P”, which
could result in an accident or serious injury.

169 Automatic transmission
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data Instruments
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cluster displayPractical hints Car care Index Neutral
No power is transmitted from the engine to the
drive axle. When the brakes are released, the
vehicle can be moved freely (pushed or towed). Do
not engage “N” while driving except to coast
when the vehicle is in danger of skidding (e.g. on
icy roads, see winter driving instructions on
page 180).
Important!
Coasting the vehicle, or driving for any other
reason with selector lever in “N” can result in
transmission damage that is not covered by the
Mercedes-Benz Limited Warranty.
The transmission automatically upshifts through
5th gear. Position “D” provides optimum driving
characteristics under all normal operating
conditions.Gear selection for special circumstances
The transmission gear ranges for special circumstances
can be selected by pressing the selector lever to the
right or the left with the selector lever in position “D”.
The gear range currently selected is indicated in the
instrument cluster display.
Briefly press selector lever in the çdirection:
The transmission downshifts, one gear at a time, in the
order “4”, “3”, “2”, “1”.
Press and hold selector lever in the çdirection:
The selector lever position display will switch to the
gear range currently selected by the automatic
transmission.
The transmission will only shift down one gear if the
gear range currently selected has already shifted to its
highest possible gear.
Briefly press selector lever in the ædirection:
The transmission will shift from the current gear range
to the next higher gear range. If the transmission is
already in gear range “D”, an additional upshift of one
gear is possible.

170 Automatic transmission
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Press and hold selector lever in the ædirection:
The transmission will shift from the current gear
directly to gear range “D”.
Important!
With transmission in gear range “D”, “4” or “3”,
upshifting from 1st to 2nd to 3rd gear is delayed
depending on vehicle speed and engine temperature.
This allows the catalytic converter to heat up more
quickly to operating temperatures.During the brief warm-up period this delayed upshift
and increased engine noise might be perceived as a
malfunction. However, neither the engine nor
transmission are negatively affected by this mode of
operation.
The delayed upshift is effective with vehicle speeds
below 31 mph (50 km / h) at partial throttle and engine
temperatures below 95°F (35°C).
To avoid overrevving the engine when the selector lever
is moved to a lower gear range, the transmission will not
shift to a lower gear, if the engine’s revolutions per
minute limit would be exceeded. In this case there will
be no downshift, even when the vehicle speed reaches
the engine’s RPM limit of that gear, e.g. by applying the
service brakes. Continue driving in the usual manner.
The transmission will then shift down automatically.
To prevent the engine from laboring at low RPM when
driving uphill gradients or with your vehicle heavily
loaded, the automatic transmission will downshift when
necessary to maintain engine RPM within the best
torque range.
Wa r n i n g !
On slippery road surfaces, never downshift in order
to obtain braking action. This could result in drive
wheel slip and reduced vehicle control. Your
vehicle’s ABS will not prevent this type of loss of
control.