Question 79Motor Plants - Assistant Engineer

The correct answer is B) compression of air by the piston. In a diesel engine, the heat for igniting the fuel oil in the cylinder is generated by the compression of air by the piston. As the piston moves up in the cylinder, it compresses the air, which increases the air temperature to the point where the injected fuel oil can ignite spontaneously without the need for an electronic ignition system. The other answer choices are incorrect because: A) diesel engines do not use an electronic ignition system, C) friction in the fuel injector does not generate enough heat for ignition, and D) a separate fuel oil heating system is not necessary for the normal operation of a diesel engine.