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5.5.11. Device of prestarting heating

On the working diesel engine fuel ignites on strongly compressed and therefore hot air. At cold start there is no spontaneous ignition as spontaneous ignition temperature is not reached. The glow plugs established sideways in a forkamer create the mode of optimum ignition at the cold engine.
At engines with direct injection time of warming up is much shorter.
Besides, this device serves in the basic for decrease in toxicity of the fulfilled gases.
   Operation of the device of prestarting heating
The device of prestarting heating consists of three main knots: a strezhnevy glow plug, a timer of prestarting heating and a control lamp on the dashboard.
Glow plugs are calculated on voltage of 15 V and connected in parallel. At turn of the ignition key through each candle current about 30 proceeds And. The adjusting winding in a glow plug reduces current during about 10 with to 8-15 A. After 10 from work of a candle reach temperature of +900 °C, after 30 with – +1180 °C.
The timer of a prestarting incandescence determines duration of prestarting heating. For this purpose the relay have a sensor measuring ambient temperature. At –30 °C time of prestarting heating makes about 25 with, at +20 °C — about 4 with, at +40 °C — about 2 pages. If prestarting heating is sufficient, then the lamp of control of readiness of the engine dies away. If after the lamp went out, the engine is not started, then the safety lock cares for that it through 20–25 about the current going through candles was disconnected. If during this time the engine was started, then the device of prestarting heating is connected again during rotation of a starter.
   Glow plugs

Fig. 4.92. Bosch-Duraterm glow plugs

It "rod glow plugs of bystry start-up" (fig. 4.92). In an incandescence core which comes in a forkamer heating and adjusting windings are located one by one. With temperature increase winding resistance grows. Thereby current goes down with 30 A to 8-12 A. Each glow plug is run separately by the microprocessor of a timer of preliminary heating. In addition during the work of a candle eat small control current. The refusal of one or several candles at the working engine is signaled by a control lamp. When the engine was started, additional heating begins — it lasts to 180 with until temperature of cooling liquid reaches +40 °C. The sense of additional heating is in that at the cold car to reduce strong noise at start and to improve an exhaust. If temperature sensor on a head of the block of cylinders is faulty, then additional heating lasts generally 30 pages.
At high temperatures to which action candles are constantly subject they can fail. Especially it is influenced wrong распыл nozzles, by too low pressure of injection or the wrong moment of injection.
   Timer of prestarting heating

Fig. 4.93. Timer of prestarting heating

This relay is installed in the engine at the left arch of a wing. If to remove facing, then both nests are visible. The timer of prestarting (fig. 4.93) heating performs the following functions:
1. The relay of power regulates incandescence current.
2. Restriction of size of the given current thanks to an automatic safety lock.
3. Switching off of a control lamp at readiness of the engine for start.

The system of prestarting heating is faulty
Malfunctions of system of prestarting heating at models CDI can arise only at a frost (below -10 °C). Only then it is hard for system of direct injection to cope with start of the engine without "support" of system of heating. Malfunction of system can be determined by blue exhausts from the muffler.

4. The safety lock disconnects incandescence current if heating remains included during 20–50 with (depending on ambient temperature).
Points out malfunction of system of prestarting heating that the control lamp does not light up at inclusion of ignition.

   Malfunctions of system of prestarting heating
If the cold engine is not started or started very badly or at inclusion of ignition on the dashboard the control lamp of system of prestarting heating does not light up, it is necessary to find and eliminate malfunction. Begin search by means of a control lamp or creation of crossing points on certain electric contours. Various checks begin with both nests on a timer of prestarting heating which are easy for finding, having uncovered.
If at inclusion of heating the control lamp does not light up, then there can be following malfunctions.
1. There is no current on the 30 plug of a timer of prestarting heating.
2. The power relay is faulty.
3. It is faulty one or several wires on glow plugs.
4. Fused one or several candles of an incandescence.
5. The control lamp fused or its connecting wire is damaged.

   Refusal of a control lamp
If the control lamp does not light up in spite of the fact that the engine is started well, then, perhaps, it fused.

Fig. 4.94. Check of work of a control lamp of the device of prestarting heating: 1 – timer of prestarting heating; 2 – plug of the sensor of temperature and control lamp; 3 – control lamp; 4 – plug of glow plugs; 5 – the plug for connection of a control lamp "on weight"

1. Take out the small plug on a timer of preliminary heating of 1 (fig. 4.94).
2. Include ignition.
3. "3" plugs connect a nest to "weight". Now the control lamp has to light up.
4. If is not present — check conducting to the dashboard or replace a lamp.

   Control of tension on a timer of prestarting heating
If the engine is not started and the control lamp of prestarting heating does not light up, check food of a timer of prestarting heating.
1. The red wire always has to be alive (plug 30).
2. At the included ignition on the 15 plug has to be "+". Check a nest 1 on the smaller plug.
3. When the starter rotates, on the 50 plug also there has to be current (a nest 2).

   Check of giving of current on glow plugs
After inclusion of ignition current has to move on all glow plugs.
1. Disconnect the big plug on a timer of preliminary heating.
2. Connect a control lamp to "weight".
3. Check current one by one on all contacts of the relay. After inclusion of ignition on each contract for time of ignition has to be "+".
When checking the assistant has to switch on and off constantly ignition that all the time there was a mode of a preliminary incandescence.
If there is no current from the relay, replace the relay.

   Refusal of a glow plug
If the control lamp, perhaps does not light up, one of incandescence candles burned down. If the engine is started, then at first it works not at all cylinders. In the cylinder without preliminary heating there will be a spontaneous ignition a little later.
1. For detection of the burned-down candle disconnect the big plug from a timer.

Fig. 4.95. Detection of a faulty candle: 1 – "weight"; 2 – plug of a control lamp; 3 – a nest in the plug

2. Connect a control lamp one end on "+" (for example, to a red wire) (fig. 4.95).
3. Other end of a lamp one behind another check nests in the plug.
4. Where the control lamp did not light up, the glow plug is faulty.

Faulty candles
1. If for check there is no control lamp, it is possible to check a candle for "spark".
2. Remove the food plug on a timer of preliminary heating and a wire from "+" check one behind another of a nest. Where there is no spark, the candle is faulty.
3. If the system of preliminary heating does not work, it is possible to start the engine on the tow. The engine can be started after 1 km. Try to be brought on the tow on raised engine turns, for example on the 2nd transfer from 40 km/h (carry out carefully!).
4. If the timer was disconnected at the movement, stop, connect all wires to candles together and connect on 10-20 with to "+".

   Replacement of glow plugs
1. To reach glow plugs which are sideways at the left on a head of the block of cylinders the key - "graggers" with various heads nozzles is necessary.

Fig. 4.96. Glow plug arrangement: 1 – a glow plug with the plug; 2 – a fuel-supply line lock on the heat exchanger; 3 – heat exchanger; 4 – nozzle

2. Remove a protective cap on a candle (fig. 4.96).
3. Unscrew a candle.
4. Put a new candle and tighten with effort 20 N · m.

   Check of candles of an incandescence
The only and most reliable way of check of glow plugs — in the turned-out state.
1. If necessary remove an engine casing.
2. Disconnect wires from glow plugs.
3. Take out candles and put on a fire-resistant surface.
4. One for another connect candles by means of a thick wire (at least 2,5 mm2) and reliable plugs directly to the accumulator.
5. Check what candles poorly (such happen too), and what do not spark at all.
6. Replace faulty candles. If you want to be absolutely sure of work of candles, you can replace all set.