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E. PUMP OFF TIME TOO SHORT
Symptom: Pump is off for too short a period of time causing pump to cycle frequently.
Possible Causes: Excessive internal leakage; low precharge accumulator; leaking solenoid(s); damaged master cylinder/booster assembly.
1. Turn off ignition. Depressurise the accumulator.
WARNING: Ensure the accumulator is fully depressurised (apply brake pedal hard and release at least 40 times with ignition off) before removing accumulator.
Remove accumulator and install pressure gauge T000T1112. Install accumulator on pressure gauge adaptor.
2. Turn ignition on to let pump run for 15 seconds. Turn ignition off and apply the brake pedal hard and release up to 40 times to de-pressurise accumulator.
3. Observe pressure gauge while turning on ignition. Is there a sudden jump in pressure from 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 because the precharge is too low.
4. Allow the system to pressurise until the pump shuts off. With ignition still on, determine the pump off time by moderately applying the brakes and holding the pedal in the applied position. The pump off time is the time between brake apply and pump run. (Pump run test may also be performed via 'Tech 1')
5. Refer to the chart below to determine whether the accumulator or master cylinder/booster assembly should be replaced. If pump off time is less than 50 seconds, check accumulator precharge. If accumulator precharge is less than 600 psi, replace the accumulator. If precharge is 600 psi or greater and the pump off time is less than the corresponding chart value, replace the master cylinder/booster assembly.
Accumulator Pump
Precharge Off-time
(psi) (seconds)
1200 60
1100 55
1000 50
900 45
800 40
700 35
600 30
Less than 600 Replace accumulator