Flow Divider Research
Hard starts, rough idle and uneven EGTs at low power · Reviewed October 13, 2026
Divider faults can cause starting and idle problems. Manufacturer documents identify sticking valves and contamination; field reports describe isolated cold cylinders that recover as RPM rises. This supports testing low-flow distribution, but does not establish that N6206’s divider has failed.
- Recorded part
- P/N 2576624-1 · S/N A1A9T04
- Installed
- Overhauled unit, November 19, 2025. Maintenance record (CSV)
- Applications
- Precision lists this P/N for the TIO-540-AJ1A and IO-360-L2A (inverted installation).
Manufacturer evidence
Hard starting in freezing weather
Precision reports RSA dividers sticking closed, preventing fuel delivery during starting; warming restores flow. Reports primarily involved Cessna 172s. Confirmed units require repair. This bulletin addresses freezing-temperature starts. SIL RS-84 (2007, PDF).
Rough idle from a sticking valve
Lycoming lists a sticking flow-divider valve as a cause of rough idle, and incomplete opening as a possible intermittent cause of low fuel flow. SSP-475, printed pp. 4 and 7 (PDF).
Spring configuration affects idle
For qualifying 2 psi units on several engines, including the TIO-540-AJ1A, Lycoming specifies a 4 psi replacement spring to improve idle, especially in hot weather. This does not establish that N6206 has an incorrect spring. SI 1489C (2011, PDF).
Debris: limited AVStar production batch
A manufacturing bulletin includes AV2576624-1 units with specified serial numbers from October 2015–March 2016. Retained shavings could restrict fuel and cause poor idle or roughness. A1A9T04 is absent from the listed serial numbers. No occurrences were reported at publication. AFS-SB13 (2016, PDF).
Two relevant field reports
Firsthand accounts; neither identifies the divider part number or proves a fault in N6206.
Cold cylinder at idle; apparent overfueling
On an IO-360-C4P, C2’s EGT collapsed below 700 RPM and recovered at 1,000 RPM. Full-throttle nozzle collection looked even. Leaning revived C2, and changing divider orientation repeatedly changed the symptom. The correspondent inferred unequal divider delivery and excessive richness; calibrated outlet-flow results were not published. General Aviation News, 2021.
Cold cylinder at idle; blocked outlet slot
An O-320-H2AD with Bendix injection showed very low C3 EGT at idle, normalizing near 1,400 RPM. The owner later reported a partial blockage in the divider’s C3 slot. This illustrates a restriction mechanism: low EGT alone does not establish richness. Van’s Air Force, 2019 / 2024 follow-up.
What this means for testing
At idle, the divider’s partially open valve apportions fuel. At higher flow, the valve opens fully and downstream restrictions govern distribution. AVStar AFS-IOM-02, pp. xvi–xvii (PDF).
Diagnostic implication: normal high-flow delivery cannot exclude low-flow outlet imbalance. Request an as-received bench test measuring each of the six outlets through the low-flow range, including opening, closing and cutoff behavior. Confirm the manufacturer and spring configuration; investigate temperature dependence if the starting symptoms warrant it.