A SF340's hydraulic pump was stuck in the 'Continuous Mode' after engine start. The aircraft was shutdown; power removed; and the pump continued to function oddly so the crew returned to the gate for Contract Maintenance repair. Air Carrier Maintenance originally allowed them to continue with the malfunction but the crew decided not to.
Synopsis
A SF340's hydraulic pump was stuck in the 'Continuous Mode' after engine start. The aircraft was shutdown; power removed; and the pump continued to function oddly so the crew returned to the gate for Contract Maintenance repair. Air Carrier Maintenance originally allowed them to continue with the malfunction but the crew decided not to.
Narrative
My First Officer and I were getting ready to fly. I performed the turn check and the starting engine check. I started the number two engine and all engine instruments were normal. I went to do my after start flow and the hydraulic pump starting running. I noticed the pump was not shutting off after about 10 seconds. I attempted to turn the hydraulic pump off manually; however; the hydraulic pump continued to run. Even after I shut down the number two engine; the pump continued to run. I turned both batteries off to cycle the power. Once turning both batteries back on; the pump was not running continuously. I called Maintenance Control and they said if the pump is not running continuously then the aircraft power reset the relay and it is OK to continue. I then started the number two engine followed by the number one engine. I performed the after start flow and checklist. As we were taxiing out to runway the hydraulic pump would cycle on and off; but take a little longer than normal. The First Officer and I decided to error on the side of safety and return to the gate to have maintenance make sure it was working correctly. Contract Maintenance came to the airplane and signed off the discrepancy right away.
Second reporter narrative
We should have just written up the pump immediately; instead of having Maintenance tell us that it was fine to go.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.