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Compression (Prius)

WARNING: Read service precautions before proceeding with service procedure. See SERVICE PRECAUTIONS .
  1. Manufacturer states procedure using Toyota hand-held tester. Warm engine to normal operating temperature. Shut engine off. Remove air cleaner assembly. Disconnect electrical connectors at ignition coils. Remove ignition coils and spark plugs.
  2. Connect Toyota hand-held tester to data link connector No. 3 at driver's side of instrument panel. See Figure. Select CRANKING MODE on Toyota hand-held tester using hand-held tester instructions. Refer to Toyota hand-held tester operator's manual for further details.
  3. Check compression pressure by inserting compression gauge into the spark plug hole. Fully open the throttle. Crank the engine and note the compression. While in the CRANKING MODE, cranking speed is automatically set at 250 RPM and throttle is automatically opened to fully open position. Read compression in a short a time as possible. Ensure compression is within specification. See COMPRESSION SPECIFICATIONS  table. Remove hand-held tester.
  4. If the cylinder compression is low, pour a small amount of engine oil into the cylinder through the spark plug hole and inspect again. If adding oil increases the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged. If pressure stays low, a valve may be sticking or seating improperly, or there may be leakage past the gasket.
  5. Install and tighten spark plugs to 13 ft. lbs. (18 N.m) and ignition coil retaining bolts to 80 INCH lbs. (9.0 N.m).
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