Component description for glow plugs - GF15.20-P-4020P

ENGINES 642 in MODEL 164.1/8, 203.0/2, 221.0/1, 251.0/1 up to Model Year 08/Modification Year 07 

ENGINES 642 in MODEL 209.3/4 

ENGINES 642.920 in MODEL 211.022 except CODE (494) USA version 

ENGINES 642.920 in MODEL 211.022/222 except CODE (498) Japan version 

ENGINES 642.921 in MODEL 211.084/089/284/289 

ENGINES 642.920 in MODEL 211.020/220/620, 219.322 

ENGINES 642 in MODEL 461.3, 463.3 

Location 

The glow plugs are screwed on under the rail on the left and right in the cylinder heads.

Task 

The glow plugs warm the combustion chamber in order to reach and secure the required ignition temperature of the fuel-air mixture under all operating conditions.

Body 

The glow plugs consist of a heater tube which is pressed firmly and gas-tight into the plug housing. The heater tube consists of a hot gas and corrosion-resistant pipe which carries on the inside a glow coil embedded in compressed magnesium oxide powder. The glow coil consists of 2 series resistors.

The sensor coil housed in the tip of the glow pipe consists of a material with a positive temperature coefficient. The heating coil consists of a virtually temperature-independent resistance.

The heating coil is welded for contacting at the ground end in the round end of the glow tube. The sensor coil is contacted at a plug connector over which connection is made to the on-board electrical system.

These are:

• The sensor coil
• The heating coil

Function 

Application of the voltage to the glow plugs initially causes the majority of the electrical energy to be converted into heat in the heating coil. The temperature of the plug tip increases steeply. The temperature of the sensor coil also increases after some delay and thus also the resistance. The power consumption and thus the overall performance of the glow plugs come close to the balanced condition.