Caution: On the 1MZ-FE V6 engine, disconnect the electrical connectors from the ignition coils.
Measuring oil pressure on the 5S-FE engine
Measuring oil pressure on the 3VZ-FE engine
Location of oil pressure sensor on the front side of the 1MZ-FE engine
Installing a compression gauge into the spark plug hole to measure compression in the cylinders
In case of a decrease in engine power, which is not a defect of the ignition or fuel system, a compression test can determine the condition of the engine. If the test is performed regularly, it is possible to determine the defect that will appear soon.
The engine must be warmed up to operating temperature. The oil level must be normal and the battery must be fully charged. The help of an assistant will also be required.
1. Remove all spark plugs from the engine.
2. Remove the central high-voltage wire from the distributor cap and connect it to ground. Open the fuel pump power supply circuit.
3. Screw the compression tester tip into the spark plug hole of cylinder No.1.
4. Have the assistant press the accelerator pedal all the way down and crank the engine with the starter for a few seconds. Watch the compression gauge. The pressure will rise fairly quickly in a healthy engine. Low pressure on the first stroke, followed by a gradual increase in pressure on subsequent strokes, indicates worn piston rings. Low pressure on the first stroke that does not increase further indicates leaky valves or a blown head gasket. Deposits on the back of the valve seats can also contribute to low pressure. Record the highest pressure, then repeat the procedure for the remaining cylinders.
5. Due to the variety of compression gauges and the engine crankshaft speed of the starter, the data often differs when checking compression. For this reason, the actual compression pressure is not indicated, but the most important factor is that the pressures should be the same in all cylinders.
[The material was taken from a resource: www.toyotaman.ru]
6. Add a small amount of engine oil to the cylinders (approximately 20 cm³) through the spark plug hole and then repeat the test.
7. If there is an increase in pressure after oil is added, it is an indication that the piston rings are worn. If the pressure does not increase, there is a leak in the valves or head gasket. Leaking valves can be caused by burnt valve seats or heads, or bent valves.
8. If two adjacent cylinders have equally low pressure, it is most likely that the cylinder head gasket has blown between them. The appearance of coolant in the combustion chambers or on the dipstick confirms this defect.
9. If the pressure in one cylinder is approximately 20% lower than the other and the engine has a slightly rough idle, a worn cam lobe on the camshaft may be the cause.
10. After checking, install the spark plugs and reconnect the high-tension wires and ignition coil. Restore the fuel pump power supply circuit.