In the true diesel engine, only air is initially introduced into the combustion chamber. The air is then compressed with a compression ratio typically between 15:1 and 23:1. This high compression causes the temperature of the air to rise. At about the top of the compression stroke, fuel is injected directly into the compressed air in the combustion chamber. This may be into a (typically toroidal ) void in the top of the piston or a pre-chamber depending upon the design of the engine. The fuel injector ensures that the fuel is broken down into small droplets, and that the fuel is distributed evenly. The heat of the compressed air vaporizes fuel from the surface of the droplets. The vapour is then ignited by the heat from the compressed air in the combustion chamber, the droplets continue to vaporise from their surfaces and burn, getting smaller, until all the fuel in the droplets has been burnt. Combustion occurs at a substantially constant pressure during the initial part of the power stroke. The start of vaporisation causes a delay before ignition and the characteristic diesel knocking sound as the vapour reaches ignition temperature and causes an abrupt increase in pressure above the piston (not shown on the P-V indicator diagram). When combustion is complete the combustion gases expand as the piston descends further; the high pressure in the cylinder drives the piston downward, supplying power to the crankshaft. 
Part of their recommendations to consumers is to only use trained, experienced mechanics. Prospective students can receive that training from accredited auto mechanic schools in Massachusetts. There are multiple educational paths to this training: diploma, certificate and associate degree programs. Students can find these programs at vocational schools and community colleges. Depending on the specific degree or diploma curriculum, some programs may be completed in as little as a year, while associate degrees may require two or more years of study and training to complete.
Pay by Experience for a Diesel Mechanic has a positive trend. An entry-level Diesel Mechanic with less than 5 years of experience can expect to earn an average total compensation of AU$52,000 based on 248 salaries provided by anonymous users. Average total compensation includes tips, bonus, and overtime pay. A Diesel Mechanic with mid-career experience which includes employees with 5 to 10 years of experience can expect to earn an average total compensation of AU$62,000 based on 282 salaries. An experienced Diesel Mechanic which includes employees with 10 to 20 years of experience can expect to earn an average total compensation of AU$65,000 based on 213 salaries. A Diesel Mechanic with late-career experience which includes employees with greater than 20 years of experience can expect to earn an average total compensation of AU$70,000 based on 118 salaries.