Date: 201605
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Cessna 210 Centurion / Turbo Centurion 210C; 210D
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Descent
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Reciprocating Engine Assembly
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Private; Flight Crew Instrument
Human factors: Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft; Procedure; Human Factors
Primary problem: Human Factors

Narrative: New engine overhaul installed; 5.5 hours were flown locally before the extended trip was taken. 40-45 min prior to arrival at my destination; a reduction in fuel pressure was noted. Low boost pump was engaged and it appeared to mitigate the issue; although full normal pressure did not appear to be achieved. 30 minutes prior to arrival at my destination ATC started my descent sequence; no abnormal issues were noted north and through the Class Bravo area. ATC vectored me into the Corridor for the approach to ZZZ. As the aircraft was dropping below the Class Bravo on the descent being set-up for the approach to ZZZ at 5000 ft and 10 miles from ZZZ at lower MP and RPM; fuel pressure went from 60-80 LBS/HR to 0 LBS/HR and the engine started running rough and was proceeding to quit and the aircraft started to descend; low boost pump was ineffective. Notified ATC of the issue. ATC notified me of landing locations and distances. I selected [a suitable airport] within gliding distance and a 90 degree turn to the runway from my current position at the time. ATC wanted to know if they should dispatch equipment I indicated unlikely as I had the field made. Started to diagnose the problem; when I depressed and held the high boost pump fuel pressure on the gauge started to rise and the engine began normal operation. I notified ATC of the situation and indicated I had enough power to complete the flight to ZZZ. ATC indicated they had not completed the process and would cancel. I continued the flight to ZZZ and held the high boost pump until the field was made.I went out to the field [the next day] and removed the aircraft cowl to investigate the problem as it did not appear to be or respond like the known T210 vapor lock issue. Upon inspection I discovered the bolt for the engine mixture control and cockpit mixture control mechanism missing and the mixture control lever in the down or in or near the idle cut off position. There is no spring or other mechanism to hold the mixture control mechanism in the up or full rich position. Aircraft and engine vibration causes the control arm to move to the lean or idle cut off position. Subsequently sought out a maintenance facility on the field to correct the discrepancy.




Synopsis: C210 pilot with a freshly rebuilt engine reported a reduction in fuel pressure approaching the destination. The low boost pump was engaged and appeared to mitigate the problem. During descent pressure began to drop again and high boost pressure was used to keep the engine running to landing. Post flight inspection revealed a bolt securing the mixture lever was missing allowing the mixture to move on its own to near idle cut off.