Shutting the fluid discharge of an air-operated reciprocating pump will cause the pump to:

In the context of an air-operated reciprocating pump, shutting the fluid discharge effectively creates a condition where the pump has nowhere to discharge the fluid it is trying to move. This situation can cause the pump to 'overstroke,' which refers to the condition where the pump’s piston continues to move without successfully discharging fluid.

When the discharge is closed, the pump's cycle is disrupted, leading to excessive pressure within the pump and may force the piston to continue its stroke against a dead end. This can eventually result in mechanical failures or damage to the pump if this condition persists.

Understanding the fundamental operation of reciprocating pumps is important here. These pumps rely on a back-and-forth motion to create pressure; when that motion is not met with a discharge path, the mechanics of the operation lead to overstressing the pump components and the possibility of overstroking.

In contrast, the other outcomes listed are not a direct result of shutting the fluid discharge. For example, the pump will not reverse direction or lift the relief valve in a standard operating scenario when discharge is stopped—these are separate functionalities reliant on other conditions. Being aware of how the pump operates under normal and abnormal conditions helps prevent potential damage and informs maintenance practices.