Notes on avoiding damage to ignition system - AH15.10-P-0002-01D

ENGINE 104, 111, 112, 113, 119, 120, 156, 271, 272 

With gasoline injection and ignition system ME-SFI 

• To avoid damage to control unit, only connect and disconnect the two connectors on control unit when ignition is switched off.
• Terminal 1 of ignition coils must not be short-circuited to GND, e.g. as antitheft protection.
• Only install original ignition system components.
• Do not operate ignition system at starting speed unless all of the ignition cables are connected.
• No tests such as holding ignition cable 4 at a distance to GND, unplugging a spark plug connector or pulling cable 4 out of the ignition coils, may be performed at starting speed or when the engine is running.
• Every high voltage circuit must be loaded with at least 2 kΩ (spark-plug connector).
• If it is necessary to test the ignition spark when providing roadside assistance, this must only be done with a spark plug at a cylinder ignition cable. Ensure that spark plug has good contact to ground.
• Before working at cranking speed, e.g. checking compression pressure, switch off ignition and disconnect connector "2" from control unit.

Engine 120 has two injection/ignition systems.

Use of testers and testing units 

• Only connect and disconnect secondary measuring sensor to corresponding ignition cables when vertical engine and ignition are switched off.
• If the short-circuit protection is operated (cylinder comparison) and the engine stays upright, it is not possible to conduct the test with this test instrument.
• Do not connect test lamp to ignition coil terminals 1 and 15.