Lincoln 2010 MKX Owner's Manual page 248

Roadside Emergencies
3. Connect the negative (-) cable to the negative (-) terminal of the
assisting battery.
4. Make the final connection of the negative (-) cable to an exposed
metal part of the stalled vehicle's engine, away from the battery and the
carburetor/fuel injection system.
Note: Do not attach the negative (-) cable to fuel lines, engine rocker
covers, the intake manifold or electrical components as grounding
points.
WARNING: Do not connect the end of the second cable to the
negative (-) terminal of the battery to be jumped. A spark may
cause an explosion of the gases that surround the battery.
5. Ensure that the cables are clear of fan blades, belts, moving parts of
both engines, or any fuel delivery system parts.
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