Jet pump hums but will not start; may trip breaker after a few seconds.

Safety first: Turn off power at the GFCI breaker.

• Check for obstructions: Remove the pump motor from the wet end if accessible and inspect the impeller for debris or foreign objects.
• Try manual rotation: With the pump disconnected from power, attempt to spin the motor shaft by hand. If it is stiff or seized, the motor likely needs replacement.
• Inspect start capacitor: Many Marquis jet pumps have an external capacitor under a metal or plastic cover on the motor. Look for bulging, leaking, or burned capacitors. Replace with the exact microfarad rating if defective.
• Verify voltage (advanced): A qualified person can measure voltage at the pump terminals when it is commanded on. Low voltage can prevent starting and indicates a wiring or breaker issue.

If the motor remains unable to start after capacitor replacement and mechanical checks, replace the entire pump motor assembly.