Mercedes S-Class W-140

1991-1999 of release

Repair and car operation



Mercedes S-Class
+ Mercedes-Benz Cars of a class S (W-140)
+ Operation manual
+ Routine maintenance
+ Engine
+ Systems of cooling, heating
+ Power supply system and release
- Engine electric equipment
   - Ignition and engine management systems - the general information
      Checks of a control system by ignition and injection
      Search of malfunctions - the general information and preliminary checks
      Check and adjustment of a corner of an advancing of ignition
      Spark plugs
      Self-diagnostics of systems of electronic control of OBD
      Diagnostics of electronic system of the automatic conditioner of air (KV)
      Oscillograph application for supervision of signals of a control system
      Ignition coils - installation details
      Removal, installation and adjustment of the sensor of provision of a camshaft (CMP)
      The ignition distributor (M119.97 engines) - installation details
   + charge and start Systems
+ gear shifting Box
+ Avtomaticheckaya transmission
+ Coupling
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment



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Checks of a control system by ignition and injection

General information

Components of system of ignition are very reliable. Malfunctions are, as a rule, connected with unreliability or pollution of contacts. Breakdowns of high-voltage wires arise because of pollution, humidity or isolation damage, instead of because of malfunction of components of system more often. Before drawing a conclusion on malfunction of any component, check its conducting.

To check operability of a high-voltage wire, having removed it from a candle and having approached to an engine surface (watching spark existence), it is impossible. You risk not only to receive blow a current, but also to damage the control unit or the ignition coil. If the engine works unstably, never remove tips of wires from candles for definition of the faulty.

Described below check it is necessary to carry out, if malfunction is obvious (starter refusal, admissions of ignition, etc.). Some malfunctions are less obvious and can not be shown because the control system of the engine was switched in a mode of safe functioning. This sort of malfunctions are shown in increase of fuel consumption, instability of turns of idling, loss of capacity, a detonation etc. If you found similar symptoms, address on HUNDRED.

The engine is not started

Keep in mind that at failure of the anti-theft device you cannot start the engine. Disconnect the device (address to Head the Operation manual)


If the engine is not turned at inclusion of a starter or turned very slowly, check a starter and the storage battery. Attach the voltmeter to plugs of the battery and measure tension at a provorachivaniye of the crankshaft of the engine by a starter. Do not include a starter more than for 10 seconds. If the voltmeter shows 9.5 In and less, be convinced of serviceability of the storage battery, a starter and charging system.

If at starter inclusion the engine rotates with usual speed, but is not started, check all high-voltage components of system of ignition.

Following instructions of the manufacturer, connect a stroboscope and turn the engine crankshaft a starter. If the lamp on a stroboscope lights up, tension arrives on spark plugs. Be convinced of serviceability of candles. If the lamp is not lit, check high-voltage wires (see. Head Routine maintenance). If candles or wires are serviceable (a spark is), follow the recommendations provided in the Section Search of malfunctions - the general information and preliminary checks.

If the spark is not present, be convinced of serviceability of the coil of ignition (or replace the coil on obviously serviceable or check resistance of windings). If malfunction is not found, look for it in other place. If after coil replacement the engine started to be started - malfunction is found. Do not hurry to throw out the coil and to buy the new. Be convinced of reliability of accession of conducting to the coil (the engine could not be started because of the oxidized contact).

If the coil as it should be, it is faulty, possibly, the powerful buffer target cascade being a component of the control unit of the engine, one of sensors of a control system of the engine or the accompanying knot. In this case in memory of the control unit the code of malfunction which it is possible to consider from memory should be written down.

It is possible to consider codes of malfunctions by means of the special equipment.

Ignition admissions

The reason of admissions of ignition is unreliable contact of conducting to plugs of the coil of ignition or any sensor more often.

Switch off ignition and be convinced of reliability of connection of all sockets of system of ignition.

Check high-voltage wires. Be convinced that they are reliably fixed in points of intermediate fastenings and do not adjoin to metal parts of the engine. If the wire concerns some metal and it damaged isolation, at operation of the engine the spark will be submitted not on a candle, and on weight. At detection even insignificant damage of isolation at least one wire replace all set.

To be convinced of full operability of wires it is possible, having temporarily replaced them with the obviously serviceable.

At replacement of wires change them on one. It you will avoid risk of the wrong connection. Do not damage a wire at installation.

If high-voltage wires are completely serviceable, the reason of emergence of admissions of ignition is, most likely, the coil of ignition or any spark plug. Establish a new set of candles (see. Head Routine maintenance) or check the coil (see. Section Check and adjustment of a corner of an advancing of ignition). The faulty or dirty sensor of position of the crankshaft (see can be the reason of emergence of admissions of ignition. The section Power supply system and injection of fuel of the petrol engine - the general information of Head of the Power supply system and release.

If check of aforementioned knots did not lead to improvement of operation of the engine, consider codes of malfunctions from memory of the control unit.