The diesel vehicles Ural are equipped with the KamAZ-740 engine of the third configuration. Therefore, we look at the repair and maintenance of the engine in the articles on repairing the diesel engine of the KamAZ car Kamaz engine

An engine failure in operation is determined by:

  • - power drop;
  • - increased fuel and oil consumption;
  • - reduced oil pressure;
  • - the nature of knocks and noise.

Loss of engine power affects the dynamic qualities of the car: poor acceleration, climbing in a lower gear, reduced top speed.

A drop in engine power can also be characterized by a decrease in compression in one or more cylinders.

A decrease in compression in the engine cylinders indicates wear on the piston rings and valve leaks.

Compression is measured using a compression tester on a warm engine at a coolant temperature of at least 80 ° C and at a minimum idle speed (600 rpm).

To determine the amount of compression pressure, install a compression tester instead of the nozzle in the glass of the cylinder head and clamp the nozzle mounting bracket.

Put a gas-resistant rubber hose on the fitting of the high-pressure pump section to be checked and lower its end into a vessel to collect fuel that will come from the pump section when checking compression.

Then start the engine and record the pressure shown on the pressure gauge of the device at the minimum speed of the engine crankshaft.

Measure the compression in other cylinders in the same way.

For a serviceable engine, the compression value must be at least 30 kgf/cm2, and the pressure difference in the cylinders must not exceed 2 kgf/cm2.

Reference fuel consumption, specified in the technical characteristics of the car, is determined by measuring the fuel consumption when driving a loaded car at a speed of 40 km / h in top gear in two opposite directions of a flat, horizontal asphalt section of a highway 1 km long.

If other vehicle components are in good condition, the increased control fuel consumption is a consequence of the unsatisfactory technical condition of the engine.

Increased oil consumption (in the absence of leakage) indicates wear of the cylinder-piston group, coking of the hole in the grooves for oil scraper rings, burnt rings.

Reduced oil pressure (when the lubrication system is working properly) is the result of significant wear on the crankshaft and camshaft bearings.

The causes of a sudden and sharp drop in oil pressure in the main oil line can be clogging and sticking in the open position of the oil pump valve, lubrication system, as well as emergency wear, damage to the liners of one or more bearings.

Valve sticking and emergency wear of the liners may be the result of running the engine with dirty oil.

Use a stethoscope to detect oil and determine the nature of knocks and noise.

By the tone of the knock, as well as by the place of its greatest audibility, you can determine the cause and location of the malfunction.

Strong knocks of a high (metallic) tone, which increase with increasing crankshaft speed, are characteristic of the piston hitting the valve when the spring breaks or the valve sticks in the guide.

Knocks heard in the upper part of the cylinder block, fading with an increase in the frequency of rotation of the crankshaft and increasing with its decrease, may be caused by scuffing of the working surface of the liners or pistons.

When the clearances in the joints of the piston with the piston pin or the piston pin with the upper head of the connecting rod, as well as in the main and connecting rod bearings, knocks may appear, easily heard under load, with a sharp change in fuel supply.

With an increased gap between the piston and the cylinder liner, a dull knock is heard after a cold start and subsides or disappears completely after the engine warms up.

A high tone of sound in the area of ​​​​the valves, as a rule, indicates increased gaps between the toe of the rocker and the end of the valve stem.