SYMPTOM:
PUMP WILL NOT STOP CYCLING WHEN OUTLET IS BLOCKED OR STALL PRESSURE IS ACHIEVED.

THEORY:
Assuming proper priming of the pump, the reasons for a single acting plunger pump to continue cycling after system shut-off or pump stall pressure has been reached are as follows:
a. System fluid leakage. (May be external or internal in a component)
b. Internal or external pump fluid leakage.
c. False cycling of pump.
When the pump has completed a suction stroke, it can only complete the cycle if it can "dispose" of the fluid. (What goes in, must come out). Therefore, the fluid must be lost through one of the above mentioned paths, or the pump must be false cycling (covered as a separate item).

TROUBLE SHOOTING METHOD:
For item a, check the system shut-off valve or operational device (i.e. - cylinder, etc.) for possible leakage. The system should be eliminated as a source of the problem before trouble shooting the pump.

For item a. and b., see section on "Leakage"

For item c, see section on "False Cycling"