(F) Pump Off Time Too Short

SYMPTOMS: Pump runs periodically or frequently with no brake apply, pump runs every 20 seconds or less with brakes steadily applied, pump runs every time brake is depressed.

POSSIBLE CAUSES: Excessive internal leakage, low accumulator precharge, leaking solenoid(s), damaged Powermaster III Unit.

INSPECT

Adapter And Gauge Connection:

1. Depressurize the system, refer to "Depressurizing the Powermaster III Unit" in Service and Repair. Remove accumulator and install J 37118. Install accumulator on J 37118.
2. Turn on the ignition, check for leaks, correct as necessary then depressurize the Powermaster III Unit. Perform "Total Pump Run Time Test" using 94-00101-A simultaneously. Observe the pressure gage while turning on the ignition.
3. Observe J 37118 while turning on ignition. Is there a sudden jump in pressure from 0 to 3448 kPa (0 psi to 500 psi) or more almost immediately after the ignition is turned on? (This initial jump in pressure is the amount of accumulator precharge). If not, the accumulator must be replaced.
4. Allow the system to pressurize until the pump shuts off. With ignition still on, determine the pump off time by moderately applying the brakes and holding the brake pedal in the applied position. The pump off time is the time between brake apply and pump run. To determine the pump off time without a stopwatch, perform a Powermaster III bleed down check with brake pedal depressed using 94-00101-A.

Accumulator Precharge And Time Comparison:

5. Refer to the illustrated chart to determine whether the accumulator or Powermaster III Unit should be replaced. If pump off time is less than 50 seconds, check accumulator precharge. If accumulator precharge is less than 4137 kPa (600 psi), replace the accumulator. If precharge is 4137 kPa (600 psi) or greater and the pump off time is less than the corresponding chart value, replace the Powermaster III Unit.