© 2020 Pierce Manufacturing Inc. All Rights Reserved. Pre-Trip Inspections / 5-9
OPERATION
Brake Testing
Secure all loose articles in cab, fasten seat belts, and start the engine.
Test the Rate of Air Pressure Buildup
Time the rise in pressure from 85 to 100 psi with the engine at operating rpm. Pressure should build from 85 to
100 psi within 45 seconds. (If the vehicle has larger than minimum air tanks, the buildup time can be longer and
still be safe.) If air pressure does not build up fast enough, pressure may drop too low during driving, requiring an
emergency stop. Do not drive until the problem has been repaired.
Test Air Leakage Rate
1. Run the engine to fully charge the air system to 125 psi.
2. Turn off the engine and release the service brake.
3. Time the air pressure drop. The loss rate should be less than 2 psi in one minute for single vehicles.
4. Apply 90 psi or more with the brake pedal. After the initial pressure drop, the pressure should not fall more
than 3 psi in one minute.
If the leakage rate is greater than 3 psi per minute, check for air leaks and fix before driving the vehicle.
Test Air Compressor Governor Cut-In and Cut-Out Pressure
The air compressor should start pumping at about 100 psi and stop at about 125 psi.
1. Operate the engine at a fast idle and monitor the pressure at the gauge.
2. Listen for the air pressure governor to cut out (indicated by a pressure discharge from the air dryer and a halt
to the rise of the gauge needle). The air governor should cut out the air compressor at about 125 psi.
3. Operate the engine at idle.
4. Apply and release the brake pedal to reduce the air tank pressure. The compressor should cut in at about
110 psi (indicated by a rise in the pressure at the gauge)
PRE-TRIP AND DAILY VEHICLE INSPECTIONS
PERFORM DAILY AT THE BEGINNING OF EVERY WORK PERIOD
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