Compression check in engine cylinders

For accurate results, test compression engine warm up to normal temperature, the battery must be fully charged.

The values of compression in engine cylinders allow to judge a condition of group of details in the upper part of the engine (pistons, piston rings, valves, cylinder head gasket). The decrease may be due to compression Leaking combustion chambers due to wear of piston rings, plates and damage to the valve seat, burn-out cylinder head gasket.

Start up the engine and warm up to normal operating temperature, then stop and wait for 10 minutes to reduce the temperature of the catalytic converter.

Clean the areas next to the spark plugs for what blow compressed air (in the absence of the compressor blow sites automobile or a bicycle pump). This is necessary in order to prevent the penetration of dirt into the cylinders at compression measurement.

Remove all spark plugs.

Disable the ignition system by disconnecting the primary winding of the ignition coil from the ignition distributor.

Fully open the throttle.

Insert a compression gauge into the well of the candles.

Include a starter and turn the crankshaft by at least seven of the compression stroke, follow indications compression tester (Fig. 2.24). On the serviceable engine pressure should accrue quickly. Low pressure after the first piston stroke and slow increase at the subsequent steps of compression point to the deterioration 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 leaking cylinder head gasket (the reason may lie in the formation of cracks in the head). Compression decrease can be caused by deposits of carbon on the reverse sides of the valve plates. Record highest compression setting.

Measure the compression in other cylinders and compare the results with those given at the beginning of the technical data section.

If the compression is below the minimum allowable value, enter into each cylinder through the spark plug hole a little engine oil, then recheck. If, after the introduction of oil the compression has raised, it is possible to draw an unequivocal conclusion that piston rings are worn out. If the compression is increased slightly, the leak occurs through valves, or cylinder head gasket. Leak through valves can be caused by a burn-out of saddles and / or working edges of valves, valve stem deformation or formation of cracks on them.

If a compression equally low only in two next cylinders, the most likely reason is the lining burn-out between them. As acknowledgment may appear in the combustion chamber or the oil pan traces of coolant.

If compression in one of the cylinders is lower than the other, and unstable engine runs at idle, then the reason may be wear of the cam camshafts.

If the compression exceeds the nominal value, then to the combustion chamber carbon deposits. In this case, the cylinder head must be removed, and remove carbon deposits.

If the compression in all cylinders low or strongly differs for different cylinders, check for tightness of the combustion chamber, which refer to a specialized body shop. The test results must be accurately installed leaks and Quantitative characterization of the leak.

After checking the compression release the throttle and ignition system restore.