Mercedes S-Class W-140

1991-1999 of release

Repair and operation of the car

Diagnostics of malfunctions

The description of diagnostics of electronic control systems and diagnostic codes are provided in the Head Elektrooborudovaniye of the engine.

In this Section the simplest scheme of clarification of the reasons of the malfunctions and refusals happening in knots and systems of the vehicle is offered. Refusals and their possible reasons are broken into groups on a sign of the relation to certain components or systems of the car, such as the engine, the cooling system, etc., besides, in the text references to Chapters and Sections concerning these problems are given.

Remember that the successful completion of search of causes of defect is not the black magic available only to skilled professional mechanics at all, and is defined by a combination of a certain knowledge and patient, systematic approach to a problem research. It is necessary to move always from simple to difficult, to bring each check to the logical end and to try not to pass the obvious facts - everyone can forget to fill fuel in the fuel tank or to leave included in lighting fixtures for the night.

And at last, it is always necessary to try to make a clear picture of development of malfunction and to take the corresponding steps for prevention of a recurrence. If the failure of electric equipment happened for a cause of infringement of quality of contact, check a condition of all other contacts and electric sockets of system at the same time. If the same safety lock several times in a row continues to fuse, there is no sense in its further replacement - it is necessary to try to find out a cause of failure. Remember that failure of a minor component can be a sign of violation of functioning of more important knot or the whole system.

The engine is not turned in attempts of its start

1. Corrosion of plugs of the battery takes place or fastening of tips of wires on them weakened. Check a condition of plugs and tips. Tighten terminal clips, if necessary remove corrosion traces.
2. The battery is discharged or faulty. If tips of wires are found by pure and reliably fixed on battery plugs, turn the ignition key in position of ON, then include head headlights and/or screenwashes. If this electric equipment does not function, the battery is discharged.
3. Transmission it is inexact it is established in situation "P".
4. Conducting in a chain of system of start is torn off or fastening of wires on plugs weakened. Check a condition of rovod, plugs and electric sockets of the battery, traction relay of a starter and the lock of ignition.
5. The gear wheel of a starter is jammed in a gear wreath of a driving disk. Try to turn the engine for a crankshaft pulley. At the first opportunity remove a starter and check a condition of a gear wheel and a gear wreath.
6. The traction relay of a starter is faulty (see the Head Elektrooborudovaniye of the engine).
7. The starter is faulty (see the Head Elektrooborudovaniye of the engine).
8. The ignition lock is faulty.

The engine is turned, but not started

Petrol models

1. Start is incorrectly made (see appropriate section of the Head the Operation manual).

Order of start of the petrol engine

Stability of operation of the engine on single turns is broken

Petrol models

1. Depression losses take place. Make sure of reliability of an inhaling of fixing bolts / nuts, check the fact and quality of fastening on the unions on the inlet pipeline of all vacuum hoses. Wiretap the working engine by means of a stethoscope or a piece of a fuel hose. Existence of the hissing sound will allow to reveal a source of "leak" of vacuum. It is possible to use solution of soap water for check not less effectively.
2. Malfunction of components of a power supply system or electric equipment takes place (see Chapters of the Power supply system and release and engine Electric equipment).
3. The valve of system of the operated ventilation of a case is blocked (see the Head Dvigatel).
4. The air filter is blocked (see the Head of the Power supply system and release).
5. The fuel pump does not provide giving of enough fuel to injectors of system of injection (see the Head of the Power supply system and release).
6. Leaks through laying of a head of cylinders take place. Perform measurement of compression pressure in engine cylinders.
7. Working ledges of cams of the camshaft are worn-out (see the Head Dvigatel).

Diesel models

1. Quality of connections of fuel hoses on TNVD and the fuel filter is broken. Replace fuel hoses, fix them by collars, tighten screws of angular connections.
2. Fastening of TNVD is mechanically damaged or weakened. Check fastening.
3. Are mixed by junctions of the returnable pipeline and pipeline of supply of fuel. Put connections on the places. The screw of connection of the returnable pipeline has marking of "OUT".
4. Damage to the line of supply of fuel takes place:
      a) Pipelines or hoses are mechanically damaged or littered, - clear fuel pipelines;
      b) The fuel filter is littered. Replace the filtering element.
      c) It is necessary to check the filter and pipelines for availability of ice or wax in the winter, - drive the car into the heated garage, add to system of gasoline;
      d) Ventilation of a tank or the mesh filter of a toplivozabornik is littered, - clean.
5. Adjustment of the beginning of supply of fuel is brought down. Check, make adjustment.
6. Nozzles are faulty. Check. Turn off consistently cap nuts - at an otvorachivaniye of a nut of the faulty cylinder turns of the engine will not fall.
7. The fuel pump of high pressure (FPHP) is faulty. Establish new, or obviously serviceable TNVD for check.

Admissions of ignition on single turns take place

1. Spark plugs are worn-out or polluted or the candle gap is incorrectly exposed (see the Head Elektrooborudovaniye of the engine).
2. Malfunction of components of a power supply system or electric equipment takes place (see Chapters of the Power supply system and release and engine Electric equipment).
3. Wires of spark plugs are faulty (see the Head Elektrooborudovaniye of the engine).
4. Low-quality fuel is filled. The fuel filter is hammered.
5. Losses of depression in the inlet pipeline or through hose connections take place.
6. There is not enough, or compression pressure in cylinders is distributed unevenly. Perform measurement of a compression (see the Head Dvigatel).
7. Violations in work of a control system of the engine take place.

Admissions of ignition take place during the movement on transfer

1. The fuel filter is blocked or pollution of a power supply system takes place (see the Head of the Power supply system and release).
2. Spark plugs are faulty or polluted or the candle gap is incorrectly exposed (see the Head Elektrooborudovaniye of the engine).
3. Malfunction of components of a power supply system or electric equipment takes place (see Chapters of the Power supply system and release and engine Electric equipment).
4. Defect of candle wires takes place (see the Head Elektrooborudovaniye of the engine).
5. Components of systems of decrease in toxicity of the fulfilled gases are faulty.
6. There is not enough or compression pressure is distributed between cylinders unevenly. Remove spark plugs and perform measurement of compression pressure (see the Head Dvigatel).
7. The system of ignition is faulty (see the Head Elektrooborudovaniye of the engine).
8. Losses of depression on the throttle case, the inlet pipeline or through vacuum hoses take place.

The engine spontaneously becomes deaf

1. Adjustment of turns of idling is broken.
2. The fuel filter is blocked and/or moisture or dirt got to a power supply system (see the Head of the Power supply system and release).
3. The refusal of components of a power supply system or sensors takes place (see the Head of the Power supply system and release).
4. Components of systems of decrease in toxicity of the fulfilled gases are faulty.
5. Spark plugs are faulty or polluted or the candle gap is incorrectly exposed (see the Head Routine maintenance). Also check a condition of candle wires (see the Head Elektrooborudovaniye of the engine).
6. Losses of depression on the case of a throttle or through vacuum hoses take place.

The engine does not develop full capacity

1. Malfunction of components of a power supply system or electric equipment takes place (see Chapters of the Power supply system and release and engine Electric equipment).
2. The air cleaner is littered. To clean or replace.
3. Spark plugs are faulty or the candle gap is incorrectly exposed (see the Head Routine maintenance
4. The ignition coil is faulty (see the Head Elektrooborudovaniye of the engine).
5. AT liquid level does not conform to requirements (see Chapters Routine maintenance and Automatic transmission).
6. Transmission revolves (see the Head Stsepleniye).
7. The fuel filter is blocked and/or dirt/moisture got to a power supply system (see the Head of the Power supply system and release).
8. Fuel not of that grade is filled. Fill in in a tank fuel with the required octane number.
9. The adjusting valve of a turbocompressor is damaged
10. The activator of the camshaft of shift of phases GRM is faulty
11. Compression pressure, insufficient or uneven on cylinders. Perform measurement of a compression which analysis of results allows to reveal existence of leakages of valves and/or violation of tightness of laying of a head of cylinders (see the Head Dvigatel).

In addition for the diesel engine

1. The air cleaner is littered. Clean or replace.
2. Uneven supply of TNVD fuel on cylinders. Adjust on the heated-up engine.
3. The moment of the beginning of supply of TNVD fuel is incorrectly determined. Establish.
4. The fuel filter or TNVD (nozzle) is littered. Wash out the preliminary filter, replace an element of the filter of thin cleaning, clean a spray or replace the pump (nozzle).
5. Adjustment of the maximum frequency of rotation of a bent shaft is broken.

There are cottons in system of an admission or shots in system of release

1. Malfunction of components of a power supply system or electric equipment takes place (see Chapters of the Power supply system and release and engine Electric equipment).
2. Defect in a secondary contour of system of ignition (destruction of insulators of spark plugs or defects of candle wires) takes place (see the Head Elektrooborudovaniye of the engine).
3. The system of injection of fuel needs adjustment or its components are excessively worn-out (see the Head of the Power supply system and release).
4. Losses of depression on the throttle case, the inlet pipeline or through vacuum hoses take place.
5. Valves are jammed (see the Head Dvigatel).
6. The order of connection of candle wires is broken (see the Head Elektrooborudovaniye of the engine).

At the movement with acceleration or uphill there are detonation sounds

1. Low-quality fuel is filled.
2. Malfunction of components of a power supply system or electric equipment takes place (see Chapters of the Power supply system and release and engine Electric equipment).
3. Spark plugs not of that type are established. Check candles and coils for existence of damages (see the Head Elektrooborudovaniye of the engine).
4. Basic installations of the block of electronic control are broken.
5. The detonation sensor is faulty.
6. Depression losses take place.

Kalilny ignition takes place (the engine continues to work after switching off of ignition)

1. Idling turns are excessively high (see the Head Dvigatel).
2. Malfunction of components of a power supply system or electric equipment takes place (see the Head Elektrooborudovaniye of the engine).
3. The valve of a purge of an adsorber of system of catching of vapors of fuel (EVAP) is damaged.
4. Working temperature of the engine is excessive. Decrease in level of cooling liquid (see the Head of the Cooling system, heating), the failure of the thermostat, blocking of a radiator or malfunction of the water pump can be the possible reasons of this violation (see the Head of the Cooling system, heating).

The diesel engine smokes

1. Black smoke:
      a) The air cleaner is polluted, - wash out and fill with fresh oil or replace an element;
      b) Inappropriate fuel is applied, - wash out a tank and replace fuel;
      c) The moment of the beginning of giving of TNVD is incorrectly determined.
2. Blue smoke:
      a) Burning of oil in the combustion chamber owing to wear of piston rings, high level of oil in the air cleaner, wear of epiploons in covers of a turbocompressor, formation of thinnesses in laying between a block case and a turbocompressor, - repair the engine, establish the normal level of oil, replace epiploons, tighten bolts of fastening of a turbocompressor or replace laying;
      b) Fuel to one of nozzles does not move, - check on heating of final branch pipes of a collector;
      c) Bad dispersion of fuel a nozzle because of malfunction of the valve or break of a spray, - grind in the valve or replace a nozzle.
3. White or brown smoke:
      a) Low temperature in the cooling system, - check the thermostat;
      b) Bad work of nozzles owing to wear or break of a spray, - replace a spray.

Engine electric equipment

The battery does not "hold" a charge

1. The driving belt of the generator is worn-out or damaged, or adjustment of its tension is broken (see the Head Elektrooborudovaniye of the engine).
2. Level of electrolyte is insufficient or the battery is strongly discharged (see the Head Elektrooborudovaniye of the engine).
3. Corrosion of plugs of the battery takes place or fastening of tips of wires on them weakened (see the Head Elektrooborudovaniye of the engine).
4. The generator does not provide the required charge current (see the Head Elektrooborudovaniye of the engine).
5. The electrical wiring of a charging contour is torn off or is in any other manner damaged or fastening of wires on plugs weakened (see the Head Elektrooborudovaniye of the engine).
6. Short circuit of an electrical wiring creates continuous leakage of the current developed by the battery on "weight" (address the Head Elektrooborudovaniye of the engine and Schematic diagrams of electric equipment).
7. Internal defect of the battery takes place.

The control lamp of charging does not die away at increase in turns

1. The driving belt is weakened. Check a natyazhitel of a maple belt.
2. Damage of the obgonny coupling (only turbodiesel). Remove the generator and turn a power shaft of the generator to the left. If the working surface of a pulley does not rotate, then damage, as a rule, to the obgonny coupling.
3. Damage of the regulator of the tension/generator. Disconnect a wire (D+) from a reverse side of the generator and include ignition. If now the control lamp does not light up, malfunction, as a rule, in the regulator of tension or in the generator.
4. Wear of brushes. Visually check brushes, if necessary replace.
5. Damage of the regulator. Check, if necessary replace.
6. Damage of the generator. Check, if necessary replace.
7. Damage of a wire between the generator and the regulator of tension.
8. Damage of the block of the dashboard.

The control lamp of charging does not light up at turn of the ignition key in position of ON (at inclusion of ignition)

1. Fused or otherwise the control lamp on the dashboard failed (see the Head Onboard electric equipment).
2. The generator is faulty (see the Head Elektrooborudovaniye of the engine).
3. Defect of the printed circuit board, conducting in the block of the control panel or the boss of a lamp takes place (see the Head Onboard electric equipment).

The control lamp of a charge burns after switching off of ignition

Starter

1. If the starter is not turned, at first it is necessary to check that on the plug of the 50th traction relay there was necessary tension of at least 10 Century. If tension is lower than this value, it is necessary to check according to the scheme of a wire, entering a starter current contour.
2. Whether the starter works at a full tension of the battery, it is possible to check as follows:
      a) Not including transfers, include ignition;
      b) Peremknite starter plugs 30 and 50 a wire of section at least 4 mm2, address also the Section "Check of the Traction Relay" of the Head Elektrooborudovaniye of the engine).
3. If the starter works faultlessly, the cause of defect should be looked for in wires to a starter. If the starter does not earn, it should be checked in the removed state.

Check condition:

In places of connection of a wire have to be well fixed and should not be oxidized.

The starter does not rotate at turning on of the lock of ignition

1. The battery is discharged. Charge the battery.
2. Peremknite starter plugs 30 and 50: The starter rotates. The break of a wire 50 to the ignition lock, is faulty the starter switch. Eliminate break, replace defective parts.
3. Break of a cable or the socket of weight, the battery it is discharged. Check cables and sockets of the battery, measure battery tension, if necessary load.
4. Insufficient passing of current owing to the weakened or oxidized sockets. Clear poles and plugs of the battery, check connections between the battery, a starter and weight.
5. There is no tension on the plug of the 50th traction relay. The break of a wire, the switch of a starter is faulty.

The starter rotates slowly and does not turn the crankshaft

1. Category of the battery. Charge the battery.
2. Summer oil is filled in. Fill in all-weather oil.
3. Insufficient passing of current owing to the weakened or