Attention! On the 1MZ-FE V6 engine, disconnect the electrical connectors from the ignition coils.
Measuring oil pressure on a 5S-FE engine
Measuring oil pressure on a 3VZ-FE engine
The location of the oil pressure sensor on the front side of the engine 1MZ-FE
Installation of a compression gauge in the spark plug hole to measure compression in the cylinders
In the event of a reduction in engine power that is not an ignition or fuel system defect, a compression test can determine the condition of the engine. If the check is performed regularly, it is possible to identify a defect that will manifest itself in the near future.
The engine must be warmed up to operating temperature. The oil level should be correct and the battery should be fully charged. You will also need the help of an assistant.
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 supply circuit.
3. Screw the tip of the compression gauge into the spark plug hole of cylinder #1.
4. The assistant should fully depress the accelerator pedal and turn the engine over with the starter for a few seconds. In this case, it is necessary to observe the readings of the compression gauge. The pressure will rise fairly quickly in a healthy engine. Low pressure on the first piston stroke followed by gradually increasing pressure on subsequent strokes indicates worn piston rings. Low pressure on the first stroke that does not rise further indicates leaking valves or a blown cylinder head gasket. Deposits on the back of valve heads 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 speed of rotation of the engine crankshaft by the starter, the data often differs when checking compression. For this reason, the actual compression pressure is not specified, however the most important factor is that the pressures must be the same in all cylinders.
6. Add a small amount of engine oil to the cylinders (approx 20 cm3) through the spark plug hole and then repeat the test.
7. If there is an increase in pressure after the oil is added, it is indicative that the piston rings are worn. If the pressure does not increase, there is a leak in the valves or cylinder head gasket. Leaking valves can be caused by burnt valve seats or poppets or bent valves.
8. If two adjacent cylinders are at the same low pressure, it is most likely that the cylinder head gasket has burned between them. The appearance of coolant in the combustion chambers or on the engine oil dipstick confirms this defect.
9. If the pressure in one cylinder is about 20% lower than the other and the engine has a slightly rough idle, a worn cam on the camshaft may be the cause.
10. After checking, install the spark plugs and reconnect the high voltage wires and the ignition coil. Repair the fuel pump supply circuit.