341
If and when
Starting assistance
Introduction
If the engine fails to start because of a discharged battery, the battery of an-
other vehicle can be used to start the engine. Before starting, check the
magic eye on the battery ⇒ page 292.
For starting assistance, jump lead cables conforming to the standard
DIN 72553 are required (see the cable manufacturer instructions). The jump
lead cable must be at least 25 mm 2
in section (0.038 inches 2
) for petrol en-
gines, and 35 mm 2
(0.054 inches 2
) for diesel engines.
For vehicles whose battery is not in the engine compartment, the jump
leads should only be connected to the starting assistance connection
points in the engine compartment.
Additional information and warnings:
● Starter assist systems (Start-Stop function) ⇒ page 196
● Working in the engine compartment ⇒ page 279
● Selective Catalytic Reduction (AdBlue) ⇒ page 275
● Vehicle battery ⇒ page 292
WARNING
Incorrect use of jump leads and incorrectly jump starting could cause the
battery to explode resulting in serious injury. Please observe the follow-
ing rules to minimise the risk of a battery explosion:
● All work involving the vehicle battery and electrical system can cause
corrosion, fire and serious electric shocks. Always read and take into ac-
count the safety warnings and standards before beginning work on the
battery ⇒ page 292, Vehicle battery.
WARNING (Continued)
● The battery providing current must have the same voltage (12V) and
approximately the same capacity (see markings on battery) as the flat
battery.
● Never charge a frozen or recently thawed battery. A flat battery can al-
so freeze at temperatures close to 0 °C (+32 °F).
● If a battery is frozen and/or has been frozen then it must be replaced.
● A highly explosive mixture of gases is released when the battery is
being charged. Always keep lit cigarettes, open flames, sparks and fire
far from the battery. Never use a mobile telephone when connecting and
removing the jump leads.
● Charge the battery only in well ventilated areas given that when the
battery is charged by outside assistance, it creates a mix of highly explo-
sive gases.
● Jump leads should never enter into contact with moving parts in the
engine compartment.
● Never switch the positive and negative poles or connect the jump
leads incorrectly.
● Note the instruction manual provided by the manufacturer of the jump
leads.
CAUTION
To avoid considerable damage to the vehicle electrical system, note the fol-
lowing carefully:
● If the jump leads are incorrectly connected, this could result in a short
circuit.
● The vehicles must not touch each other, otherwise electricity could flow
as soon as the positive terminals are connected.
Safety FirstOperating instructionsPractical TipsTechnical Specifications
343
If and when
2. Connect one end of the red jump lead to the positive +
termi-
nal of the vehicle with the flat battery A ⇒ Fig. 219.
3. Connect the other end of the red jump lead to the positive ter-
minal +
in the vehicle providing assistance B.
4. For vehicles without Start-Stop system: Connect one end of the
black jump lead to the negative terminal –
of the vehicle pro-
viding assistance B ⇒ Fig. 219.
– For vehicles with Start-Stop system: Connect one end of the
black jump lead X
to a suitable ground terminal, a solid piece
of metal in the engine block, or to the engine block ⇒ Fig. 220.
5. Connect the other end of the black jump lead X
to a solid met-
al component bolted to the engine block or to the engine block
itself of the vehicle with the flat battery. However, connect it to
a point as far as possible from the battery A
.
6. Position the leads in such a way that they cannot come into contact with any moving parts in the engine compartment.
Starting
7. Start the engine of the vehicle with the boosting battery and let it run at idling speed.
8. Start the engine of the vehicle with the flat battery and wait two or three minutes until the engine is “running”.
Removing the jump leads
9. Before you remove the jump leads, switch off the dipped beam headlights (if they are switched on). 10.Turn on the heater blower and heated rear window in the vehi-
cle with the flat battery. This helps minimise voltage peaks
which are generated when the leads are disconnected.
11.When the engine is running, disconnect the leads in reverse or- der to the details given above.
Connect the battery clamps so they have good metal-to-metal contact with
the battery terminals.
If the engine fails to start, switch off the starter after about 10 seconds and
try again after about half a minute.
WARNING
● Please note the safety warnings referring to working in the engine
compartment ⇒ page 281.
● The battery providing assistance must have the same voltage as the
flat battery (12V) and approximately the same capacity (see imprint on
battery). Failure to comply could result in an explosion.
● Never use jump leads when one of the batteries is frozen. Danger of
explosion! Even after the battery has thawed, battery acid could leak and
cause chemical burns. If a battery freezes, it should be replaced.
● Keep sparks, flames and lighted cigarettes away from batteries, dan-
ger of explosion. Failure to comply could result in an explosion.
● Observe the instructions provided by the manufacturer of the jump
leads.
● Do not connect the negative cable from the other vehicle directly to
the negative terminal of the flat battery. The gas emitted from the battery
could be ignited by sparks. Danger of explosion.
● Do not attach the negative cable from the other vehicle to parts of the
fuel system or to the brake line.
Safety FirstOperating instructionsPractical TipsTechnical Specifications