Mercedes W124

since 1985-1995 of release

Repair and car operation

W124 Mercedes
+ Governing bodies and control devices
+ 2. Maintenance (diesel engines)
+ 4. Repair of 6-cylinder petrol SOHC engines
+ 5. Repair of 6-cylinder petrol DOHC engines
+ 6. Repair of the diesel engine established in the car
+ 7. Major maintenance of engines
+ 10. System of injection of BOSCH CIS-E fuel (KE-JETRONIC)
+ 11. System of injection of BOSCH HFM fuel
+ 12. Fuel system of diesel engines
+ 13. Fuel system of diesel engines
+ 15. System of ignition of 4-cylinder petrol engines
+ 16. System of ignition of four-cylinder petrol engines
   17.2. General information
   17.3. Control unit glow plugs
   17.4. Glow plugs
   17.5. The sensor of temperature of cooling liquid
+ 19. Mechanical transmission
+ 20. Automatic transmission

17.2. General information

For simplification of start of the cold engine on diesel engines the system of prestarting heating which consists of candles of an incandescence, the control unit glow plugs, a control lamp on a combination of devices, the sensor of temperature of cooling liquid and electric wires is established.

Glow plugs represent a tiny heater, on the one hand which is located a heating element, and on the other hand - contacts. In each chamber of combustion it is established on one glow plug. Before engine start on glow plugs tension moves, and candles quickly get warm, increasing temperature in the combustion chamber. The working part of a glow plug is located at the basis of a fuel nozzle. As a result injecting my fuel passes about a glow plug and heats up, therefore process of combustion of fuel improves. Besides, small particles of fuel, passing about a glow plug, light up that improves process of ignition of fuel.

Duration of time of giving of tension to glow plugs is regulated by the control unit. On early models the control unit supervises air temperature in a motor compartment. On later models the control unit supervises temperature of cooling liquid on the basis of information from the sensor which has been built in in a head of the block of cylinders. On the basis of information received from sensors of temperature, the control unit regulates time of giving of tension to spark plugs.

Fire of a control lamp on a combination of devices testifies to work of spark plugs. Within several seconds of a candle are heated to high temperature, and the control bulb dies away that serves as a signal for engine start. If attempt to start the engine after switching off of a control lamp does not become, the timer will disconnect tension from incandescence candles to avoid a discharge of the accumulator and an overheat of candles of an incandescence. If on later models the control bulb burns after engine start, means, in system of prestarting heating there is a malfunction.

It should be noted that on later models of a glow plug are disconnected not right after engine start, and after a while, allowing the engine to leave on a normal operating mode. Period of operation of candles of an incandescence after start of the engine depends on temperature of cooling liquid.

Failure even one glow plug conducts to the complicated start of the engine with interruptions in work and strong vibration.

Obgoraniye and glow plug failure malfunction of fuel nozzles often are a consequence. If there is a scorched candle, it is not enough simple replacement. It is necessary to make the check of nozzles including definition of a form of a torch of dispersion, pressure of operation and tightness. It is important, that nozzles had an accurate otsechka of fuel.