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Part Number: 2004

Flex Drive Compression Tester

Price $ 35.7143

  • 15" flex hose allows access to all cylinders
  • Side release valve permits multiple readings without removing tester
  • Includes 14 & 18mm spark plug fittings
  • Gauge is 2-1/2" (64mm) diameter with dual calibration (0-300 PSI / 0-21kg/cm-¶)

Instructions for Compression Tester #2004/2006


  1. Run engine for approximately 10 minutes or until it reaches normal operating temperature.
  2. Stop engine, disconnect & number the spark plug wires. This makes it easy to identify the wires for proper reconnection.
  3. Clean any loose dirt from around the plugs & remove them. Placing them in order on a clean surface will help to compare any compression problems with the condition of the plugs.
  4. Remove the high tension lead from the center of the distributor & ground it. On electronic ignition systems, disconnect the electronic ignition module or remove the primary battery terminal from the coil. On GM HEI, disconnect the primary lead from the distributor cap.
  5. Remove air filter & set throttle plates wide open using caution not to damage linkage or throttle body components.


  1. Thread fitting into spark plug hole.
  2. Crank the engine for at least four compression strokes, or until pressure stops rising on the gauge.
  3. Record the compression reading. Multiple readings can be taken from the same cylinder by pushing the side relief valve.
  4. Remove the tester & return gauge to zero by depressing the side relief valve. Continue to next cylinder.


  1. On a normal cylinder, the tester should record a higher pressure on each stroke until peak pressure is reached. All cylinders on the same engine should show pressure within the manufacturerG«÷s specs.
  2. If pressure fails to climb, or if it remains at the same pressure for several strokes & then starts to climb, the probable cause is a sticking valve.
  3. If the pressure on 2 adjacent cylinders are more than 20 lbs. lower than the other cylinders, the probable cause is a defective head gasket.
  4. If the pressure is considerably higher than the manufacturerG«÷s specs, probable cause is carbon build-up in the cylinder.
  5. If pressure is low or varies widely between cylinders, put a teaspoon of SAE 30 oil into each cylinder & retest. If the pressure increases considerably, probable cause is poorly seated or worn piston rings. If pressure changes little, probable leakage is through the valve.

WARNING: Cancer and Reproductive Harm - WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer, birth defects or other reproductive harm. For more information, go

Price $35.7143