Nozzles
Injectors are the completion of the diesel injection system. Their task is to inject fuel under high pressure into the vortex chamber. Only if the fuel pressure rises above 125-140 bar does the nozzle needle rise and let the fuel into the swirl chamber. At the same time, a large compression force prevents a reverse blow to the supply system from combustion pressure. Cooling and lubrication of the nozzle needle provides fuel. Since the entire amount of fuel can never be injected, the excess fuel is diverted back to the tank via the bleed pipe previously mentioned in this chapter.
The preset interval between the start of injection and ignition is only 0.002 s. The smallest inaccuracy leads to the biggest failures. A stuck atomizer needle, for example, results in irregular and excessive fuel supply, poor mixing of fuel with air due to improper atomization, uncontrolled ignition (with a gasoline engine, they would talk about a knock). This can cause the engine to run hard, making noises and knocks similar to a faulty bearing.
Knocks
Typical of a diesel is a harsh combustion noise that can also be heard on trucks. Diesel knocks strongly only during cold engine operation.
This is partly to blame for the fuel advance clutch, which works for about 3 minutes after starting the engine.
A warm diesel engine sounds almost the same as a gasoline engine.
Therefore, it is very unpleasant if knocks appear on a warm engine. The main reason is usually ignition delay, that is, too long an interval between the start of injection and the self-ignition of the working mixture. This happens for the following reasons:
- When the moment of the start of injection is shifted;
- If the nozzle needle is sunk;
- With thickened fuel, for example, summer at low temperatures;
- With too much load at low speeds;
- With too little compression pressure.
- Sometimes it is useful to clean the engine, for which they add to the fuel «Autol Desolite» or other suitable additive agent. High-speed driving on the highway often helps as well.