For receiving exact results of check of a compression the engine should be heated-up to normal temperature, and the storage battery is completely charged.
Results of check 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). Namely, reduction of a compression can be caused not by tightness of chambers of combustion 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.
Check make in the following order:
– clear sites near spark plugs for what blow the compressed air (in the absence of the compressor blow sites automobile, or even bicycle, the pump). It is necessary to exclude dirt hit in cylinders at compression measurement;
– turn out all spark plugs;
– completely open a butterfly valve;
– put out of action ignition system, having disconnected electric sockets from ignition coils. Also disconnect the electric socket of giving of tension to the fuel pump;
– insert компрессометр into an opening for a candle;
– include a starter and turn a cranked shaft at least on seven steps of compression, watching indications компрессометра. On the serviceable engine pressure should accrue quickly. Low pressure after the first piston stroke and slow increase at the subsequent steps of compression indicates wear of piston rings. If after the first piston stroke pressure low and at the subsequent steps of compression does not increase, the reason is leak in valves or a leakage of laying of a head of the block of cylinders (the reason formation of cracks in a head also can be). Decrease in a compression can be caused also by deposit deposits on reverse sides of plates of valves. Write down the greatest value of a compression;
– repeat measurement procedure for other cylinders and compare results to specifications.
If a compression in cylinders below minimum admissible value, through an opening for a candle enter into each cylinder of a little engine oil, then repeat check. If after oil introduction the compression raised, it is possible to draw an unequivocal conclusion that piston rings are worn-out. If the compression increased slightly, leak occurs 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, and also deformation of cores of valves, or formation of cracks on them.
If the compression equally low only in two next cylinders, the most probable cause is a laying burn-out between these cylinders. As confirmation emergence in chambers of combustion or the oil pallet of traces of cooling liquid is possible.
If value of a compression in one of cylinders is lower than in the others and the engine unstably works at frequency of idling, wear of cams of camshafts can be the reason.
If value of a compression exceeds nominal rate, means, the chamber of combustion is covered with deposit deposits. In this case a head of the block of cylinders it is necessary to remove and remove a deposit.
If the compression in all cylinders low, or strongly differs for different cylinders, it is necessary to carry out tests of chambers of combustion for tightness for what it is necessary to address in a specialized workshop. As a result of tests places of leaks should be precisely established and the quantitative characteristic of leak is given.
After compression check, release a butterfly valve and restore system of ignition and fuel system.