EL-740 Air Compressor Testing

Install a governor assembly to the air compressor, if one has not been installed previously. Connect an oil supply line having at least 138 kPa (20 psi) of oil pressure at the rear bearing cap. Provisions must be made for unrestricted oil drainage from the crankcase during the test. The oil return line must be 1/2 inch I.D. minimum.

If water-cooled, connect a water supply line which will permit a flow of 5.7 L (1.5 gal U.S.) of water per minute at the air compressor.

Connect the discharge port to an air tank with a known volume of 1/2 inch O.D. copper line or equivalent. The tank should have a quick-opening valve to exhaust air pressure. Connect a line from the air tank to the reservoir port to the governor.

If tests are being made in a dusty atmosphere, connect a suitable air cleaner to the air compressor air inlet opening. Connect the air compressor to a source of power (at least two horsepower) to run at 1250 rpm.

Run the air compressor at 1250 rpm pumping against a 689 kPa (100 psi) pressure for five minutes. This time should be used to adjust and test the governor. During this test, check for oil and air leakage, overheating and excessive noise. Decrease the pressure in the air tank to 0 kPa (0 psi). Close the quick-opening valve and check the build-up time from 0 to 689 kPa (0 to 100 psi) in the air tank.

The build-up time must not exceed 55.0 seconds per 100 cubic inches of tank volume for the EL-740 Air Compressor.

To determine the allowable build-up time, use the following formula:

EL-740 Air Compressor allowable build-up time (seconds) = air tank volume (cubic inches) × 0.055.

NOTE: If the air compressor is belt driven and the pulley is removed during the overhaul, it must be replaced with the same size pulley. A different size pulley will require a different size drive belt. Also, the air compressor output will change in relation to the engine rpm.

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