2.34. Check of a compression in engine cylinders

For obtaining exact results of check of a compression warm up the engine up to the normal temperature, the rechargeable battery has to be completely charged.
Values of a compression in cylinders of the engine allow to judge a condition of group of details in the top part of the engine (pistons, piston rings, valves and laying of a head of the block of cylinders). Reduction of a compression can be caused by leakage of combustion chambers owing to wear of piston rings, damage of plates and saddles of valves, a burn-out of laying of a head of the block of cylinders.
Let and warm up the engine up to the normal working temperature, then stop it and wait 10 min. that temperature of catalytic converter decreased.
Clear sites near spark plugs for what blow compressed air (in the absence of the compressor blow sites automobile or even bicycle pump). It is necessary to exclude hit of dirt in cylinders at measurement of a compression.
Turn out all spark plugs.
Put system of ignition out of action, having disconnected primary winding of the coil of ignition from the ignition distributor.
Completely open a butterfly valve.
Insert компрессометр into a candle well.

Fig. 2.24. Use of a kompressometr for measurement of a compression in engine cylinders


Include a starter and turn a bent shaft at least on seven steps of compression, you monitor indications of a kompressometr (fig. 2.24). On the serviceable engine pressure has to increase quickly. Low pressure after the first piston stroke and slow increase at the subsequent steps of compression is pointed out wear of piston rings. If after the first piston stroke pressure low and at the subsequent steps of compression does not increase, then leak in valves or leakage of laying of a head of the block of cylinders is the reason (the reason can consist also in formation of cracks in a head). Decrease in a compression can be caused by deposits of a deposit on reverse sides of plates of valves. Write down the greatest value of a compression.
Measure a compression in other cylinders and compare results to the specifications provided in the beginning of the section.
If the compression is lower than minimum admissible value, enter into each cylinder through an opening for a candle of a little engine oil, then repeat check. If after oil introduction the compression raised, then it is possible to draw an unambiguous conclusion that piston rings are worn-out. If the compression increased slightly, leak happens via valves or laying of a head of the block of cylinders. Leak via valves can be caused by a burn-out of saddles and/or working edges of valves, deformation of cores of valves or formation of cracks on them.
If the compression equally low only in two next cylinders, then is the most probable cause a laying burn-out between them. As confirmation emergence in combustion chambers or the oil pallet of traces of cooling liquid is possible.
If the compression in one of cylinders is lower, than in the others, and the engine unstably works at idling frequency, then wear of a cam of camshafts can be the cause.
If the compression exceeds nominal rate, so on the combustion chamber of adjournment of a deposit. In this case the head of the block of cylinders should be removed and removed a deposit.
If the compression in all cylinders low or strongly differs for different cylinders, then it is necessary to check combustion chambers for tightness for what address to specialized auto repair shop. As a result of tests places of leaks have to be precisely established and the quantitative characteristic of leak is provided.
After check of a compression release a butterfly valve and restore system of ignition.