4.3. Check of a compression


On the engine 1MZ-FE V6 disconnect electric sockets from ignition coils.

Measurement of pressure of oil on the engine 5S-FE

Measurement of pressure of oil on the engine 3VZ-FE

Oil pressure sensor arrangement on the forward party of the engine 1MZ-FE

Installation of a kompressometr in an opening for a spark plug for measurement of a compression in cylinders

In case of reduction of engine capacity which is not defect of ignition or fuel system check of a compression can define a condition of the engine. If check is carried out regularly, it is possible to define defect which will be shown in the nearest future.

The engine has to be heated-up up to the working temperature. Level of oil has to meet standard, and the accumulator is completely charged. Also the help of the assistant will be required.
1. Unscrew all spark plugs from the engine.
2. Remove the central high-voltage wire from a cover of the distributor and connect it to weight. Open a power-supply circuit of the fuel pump.
3. Screw in a tip of a kompressometr in an opening of a spark plug of the cylinder No. 1.
4. The assistant has to press against the stop a pedal of an accelerator and turn the engine a starter within several seconds. At the same time it is necessary to watch indications of a kompressometr. Pressure will grow quickly enough in the serviceable engine. The low pressure on the first piston stroke accompanied with the gradual increasing pressure on the subsequent courses indicates worn-out piston rings. Low pressure on the first course which does not increase further indicates leaky valves or the punched laying of a head of the block of cylinders. Deposits on a reverse side of plates of valves can promote low pressure also. Make record of the most high pressure, then repeat the procedure for the remained cylinders.
5. Because of a variety of kompressometr and speed of rotation of a bent shaft of the engine data often differ in a starter when checking a compression. For this reason the actual pressure of compression is not specified, however the most important factor is that pressure have to be identical in all cylinders.
7. Add to cylinders insignificant amount of engine oil (about 20 cm3) through an opening for spark plugs and then repeat tests.
8. If there is an increase in pressure after oil is added, indicative that piston rings are worn-out. If pressure does not increase, available leak in valves or laying to a head of the block of cylinders. Leakage of valves can be caused by the burned saddles or plates of valves or the bent valves.
9. If two adjacent cylinders have equally low pressure, it is the most probable that laying of a head of the block of cylinders burned through between them. Emergence of cooling liquid in combustion chambers or on the probe for measurement of level of engine oil confirms this defect.
10. If pressure in one cylinder is about 20% lower, than in another, and the engine has slightly rough mode of idling, the worn-out cam on distributive to a shaft can be the cause of it.
11. After check establish spark plugs and repeatedly connect high-voltage wires and the coil of ignition. Restore a power-supply circuit of the fuel pump.