Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Hazardous Material Violation; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action; General Flight Cancelled / Delayed
Aircraft; Procedure
During preflight duties; ramp personnel motioned for me to come down to the ramp; as there was a fuel spill. When I got onto the ramp; I observed a large stream of jet fuel coming from the R main fuel tank overflow. I estimated there were 20-25 gallons on the ramp. Ramp personnel were attempting to contain the spill. I notified Maintenance; and Operations. I stopped boarding.When I returned to the cockpit to enter this discrepancy in the [log book]; I was surprised to find that there was an entry for the previous day; regarding a fuel spill on the ramp. The corrective action of this was that the fuel spill was cleaned up by contract personnel. I entered the discrepancy into the [log book]; and waited for Maintenance. It appeared to me that something occurred in the fuel system that caused the R main tank to be overfilled; causing the excess fuel to be vented overboard.Maintenance personnel arrived; and I explained the issue. The technician seemed to indicate that he may defer the R main tank quantity gauge; refuel the tank; and pump a known quantity into it for our flight. This seemed odd to me; as the R main quantity read 8800 pounds; which would be a proper indication for an overfilled main tank. Maintenance attempted to transfer fuel from the R main tank to other tanks; but when this was attempted; the R main tank; which had stopped venting fuel; began to vent again. Maintenance took the aircraft out of service.There seems to be a very obvious push to get the planes out on time; regardless of maintenance status. In my case; I wanted someone to explain to me in a satisfactory manner; why this aircraft was behaving this way. It appeared that Maintenance was blaming the fuel venting on some fuel pressure issue with the fueling cart/truck. As far as I was concerned; there was an issue with the aircraft that needed to be addressed. Fortunately; Maintenance took the aircraft out of service.
B737-800 pilot reported right main tank overflow fuel spill during preflight.