The TD engine preheating system consists of the following main parts:
- a) glow plug relay. The relay not only regulates the warm-up duration based on engine temperature, but also closes the glow plug power supply circuit. The specified relay is located at location #10 of the switch panel.
- b) Coolant temperature sensor. It informs the electronic unit of the coolant temperature to decide whether the engine needs to be preheated at start-up and for how long it should last.
- c) glow plugs. The plugs are designed to warm up a cold engine before starting it, as well as during the warm-up phase to operating temperature.
The engine warm-up process consists of three phases:
- a) Warming up. When the ignition key is turned to the first position, the warming up process begins. Its duration is determined by the electronic control unit and depends on the coolant temperature. The lower it is, the longer the warming up lasts. At an engine temperature of -20°C, the glow plug relay supplies power to the glow plugs for 8 seconds. If the engine temperature is above 65°C, the warming up duration is minimal or the control unit refuses to warm up at all. Upon completion of the warming up, the control lamp on the instrument panel goes out and from this moment on, the engine can be started.
- b) Starting readiness. The driver does not always start the engine immediately after the warm-up indicator light goes out. For this reason, the system continues warming up for about 10 seconds,
- c) support. From the moment the engine starts, further warming up occurs, accompanying the engine operation. Support continues for up to 180 seconds, until the coolant temperature reaches more than 65°C.
Glow plugs
The glow tube, which contains the glow plug's heating coil, enters the swirl chamber of the cylinder (see illustration 12.0).
This coil heats the glow tube to a temperature of 800-1000°C. Only at this temperature does a cold engine start. After starting the engine, the spark plug must withstand an operating temperature of 600-900°C. Glow plugs are self-regulating. The essence of this effect of glow plugs is as follows. When starting the engine, the starter consumes a lot of electricity, as a result of which the battery voltage can drop to almost 8 V. This means that the glow plugs do not have enough voltage to warm the engine to the desired temperature. Self-regulating spark plugs bypass this obstacle, because their design ensures heating to 800-1000°C even when the battery voltage drops. Self-regulating spark plugs act selectively, adjusting to the battery voltage.
(The original article is posted on the resource: «AUDIMANUAL.RU»)