Here are some SHURflo trouble shooting tips.
PUMP WILL NOT SHUT-OFF / RUNS WHEN FAUCET IS CLOSED
* Output side (pressure) plumbing for leaks, and inspect for leaky valves or toilet.
* For air trapped in outlet side (water heater) or pump head.
* For correct voltage to pump (±10%).
* For loose drive assembly or pump head screws.
* Are the valves held open by debris or is the rubber swollen?
* Pressure switch operation.
LEAKS FROM PUMP HEAD OR SWITCH:
* For loose screws at switch or pump head.
* Switch diaphragm ruptured or pinched.
* For punctured diaphragm if water is present in the drive assembly.
A very slow leak at the toilet could easily go unnoticed.