Compression Pressure Check
WARNING: This page is about a different variant/trim than selected.
Required Special Tool:
MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
- Before inspection, check that the engine oil, starter and battery are normal. Also, set the vehicle in the following condition:
- Engine coolant temperature: 80 - 95°C (176 - 203°F)
- Lights and all accessories: OFF
- Transaxle: Neutral (P range on vehicles with TC-SST)NOTE: On vehicles for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks.
- Turn the ignition switch to the "LOCK" (OFF) position.
- Disconnect the connector of the ignition coil, and then remove all the ignition coils and the spark plugs.
- Disconnect the all of the injector connectors.WARNING: Keep your distance from the spark plug hole when cranking. Oil, fuel, etc., may spray out from the spark plug hole and may cause serious injury.
- Cover the spark plug hole with a shop towel etc., after the engine has been cranked, check that no foreign material is adhering to the shop towel.
- Set compression gauge to one of the spark plug holes.
- Cranking the engine with the accelerator pedal fully depressed, measure the compression pressure.
Standard value (at engine speed of 200 r/min): 1, 090 kPa (158 psi)
Limit (at engine speed of 200 r/min): Minimum 750 kPa (109 psi)
- Measure the compression pressure for all the cylinders, and check that the pressure differences of the cylinders are below the limit.
Limit: Maximum 100 kPa (14 psi)
- If there is a cylinder with compression or a compression difference that is outside the limit, pour a small amount of engine oil through the spark plug hole, and repeat the operations in steps from 6 to 8.
- If the compression increases after oil is added, the cause of the malfunction is a worn or damaged piston ring and/or cylinder inner surface.
- If the compression does not rise after oil is added, the cause is a burnt or defective valve seat, or pressure is leaking from the gasket.
- Connect the all of the injector connector.
- Install the spark plugs and ignition coils.
- Use the scan tool MB991958 to erase the diagnostic trouble codes.NOTE: This will erase the diagnostic trouble code resulting from the injector connectors being disconnected.
- Select "Mode $0A" from "Special Function" of Scan tool MB991958. Check whether the permanent-DTC (PDTC) is stored or not. If stored, clear the PDTC. (Refer to MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS )