TD5 Defender
18
ENGINE MANAGEMENT SYSTEM
24
DESCRIPTION AND OPERATION
GLOW PLUGS
The 4 glow plugs are located in the engine block on the inlet side, in cylinders 1 to 4. Cylinder 5 has no glow plug.
The glow plugs are a vital part of the engine starting strategy. The purpose of the glow plugs are:
•
Assist cold engine start.
•
Reduce exhaust emissions at low engine load/speed.
The main part of the glow plug is a tubular heating element that protrudes into the combustion chamber of the
engine.The heating element contains a spiral filament that is encased in magnesium oxide powder. At the tip of
the tubular heating element is the heater coil. Behind the heater coil and connected in series is a control coil. The
control coil regulates the heater coil to ensure that it does not overheat and cause a possible failure. The glow
plug circuit has its own control relay, located underneath the RH front seat.
Pre-heat is the length of time the glow plugs operate prior to engine cranking. The ECM controls the pre-heat time
of the glow plugs based on battery voltage and coolant temperature information via the glow plug relay.
Post-heat is the length of time the glow plugs operate after the engine starts. The ECM controls the post-heat time
based upon ECT information. If the ECT fails the ECM will operate pre-post heat time strategies with default
values from its memory. In this case, the engine will be difficult to start.
