During priming, which observation indicates that suction is priming?

During priming, which observation indicates that suction is priming?

• A. Suction gauge rises toward zero or above baseline
• B. Engine RPM increases
• C. Suction gauge falls away from baseline
• D. Discharge gauge reads zero

Answer: (A)

Priming a pump means clearing air from the suction line and filling the pump with water. As air is expelled and water reaches the pump, the suction pressure improves, so the suction gauge moves toward ambient pressure (zero) or even a bit positive. Seeing the suction gauge rise toward zero or above baseline is the clearest indicator that the suction side is becoming primed and water is being drawn into the pump. If the gauge falls away from baseline, it shows worsening vacuum and that priming hasn’t been achieved. Engine RPM changing isn’t a direct sign of priming, since RPM depends on throttle and load, not on the suction state. A discharge gauge reading zero doesn’t indicate priming status, because it simply shows no water is leaving the pump at that moment.

Priming a pump means clearing air from the suction line and filling the pump with water. As air is expelled and water reaches the pump, the suction pressure improves, so the suction gauge moves toward ambient pressure (zero) or even a bit positive. Seeing the suction gauge rise toward zero or above baseline is the clearest indicator that the suction side is becoming primed and water is being drawn into the pump. If the gauge falls away from baseline, it shows worsening vacuum and that priming hasn’t been achieved. Engine RPM changing isn’t a direct sign of priming, since RPM depends on throttle and load, not on the suction state. A discharge gauge reading zero doesn’t indicate priming status, because it simply shows no water is leaving the pump at that moment.