Checking technical state of a car

ELECTRICAL SYSTEMS

AND

THE FUNCTIONS OF THE FUEL

OF THE DIESEL ENGINE

FOUR STROKE CYCLE

Tractors are equipped with internal combustion engines of the diesel type. Usually they have 4 stroke engines. There are four operations in the 4-stroke cycle. They are intake, compression, power and exhaust strokes.

Intake stroke. As the crankshaft rotates it moves the piston down the cylinder by means of the connecting rod. The camshaft opens the inlet valve and the piston draws air into the cylinder. The piston reaches the BDC.

Compression stroke. The piston moves up, the inlet valve is closed and the air is compressed between the piston and the cylinder head. The temperature and the pressure of the compressed air are very high. The piston reaches the TDC.

Power stroke. At this moment the fuel pump forces the fuel through the injectors into the combustion chamber. The fuel is mixed with the compressed air. The heat of the compressed air ignites the air-fuel mixture. It explodes and provides power. During the process of combustion the gases force the piston down. It reaches the BDC.

Exhaust stroke. The piston moves up, the camshaft opens the exhaust valve, and the burnt gases escape from the cylinder. The piston reaches the TDC and a new cycle begins in the cylinder.

The function of the fuel system is to supply the explosive mixture to the engine cylinder and remove the combustion products. The basic parts of the carburetor fuel system are a fuel tank, a carburetor, air filters cleaning the fuel, inlet and exhaust pipes and a clutch to reduce the speed and noise of escaping gases. Diesel engines have a high-pressure pump forcing the fuel through the injectors into the combustion chamber.

The electrical system consists of a generator, storage battery, ignition distributor, coil, spark plugs, wires and switches. The generator is a device converting mechanical energy into electrical current. The current moves from the generator or the storage battery through the coil and is converted into high voltage current.

The distributor connected by wires to the plugs delivers high voltage to the cylinder. An electric spark ignites the explosive mixture. The electric system is used to start the engine, to feed the front and backlights, radio, windscreen cleaners and defrosters.

Checking the technical state of a car is performed visually by means of stethoscope, desselerometer, tape-measure and pressure-gauge.

Engine operation is checked at different rotation frequencies of the crankshaft. The stethoscope is used to check for noises and clatter, visually engine operation is checked for contamination by burnt gases, tightness of the lubrication system, the supply system, the cooling system, and the control devices operation at the different rotation frequencies of the crankshaft, operation of the head-lights, operation of the light switches, the windscreen wipers and the horn.

The next procedure is checking the air pressure in the tyres, and if necessary, the normalization of the pressure. Also, the oil level must be checked. The engine crankcase, gearbox and the rear end should be filled up with oil.

When the car is in motion the coupling, the gear box and the main gear are checked. The braking track and slowing down are checked on the dry road with hard covering.

The condition of the pipelines, gaskets and sealings of all units and mechanisms of the automobile and its tightness are checked visually. Heating of units is checked by touching.

When the car is in good working order, it should fulfill the following requirements: with loading acceleration the engine must operate without any clatters or pauses. The control devices should indicate the required data, gears must not slip; with continuous gear shifting, there must be no jerks: all the gears must be easy to shift into and out; without any clatters or gnash. The temperature of the units must not exceed 60⁰C.

Дата добавления: 2014-10-17