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| I don't think pressure on the Continental is used for inflight diagnosis although they are used during setup and confirmed with takeoff flows. I don't even have inflight fuel pressure readings on the Legacy. Cessna previously used pressures as a proxy for flow but that was wrong when higher pressures turned out to be injector blockage that resulted actually in lower flows. Then, flows were introduced as the primary means to manage the big TCMs. So, where is the transducer for pressure and what are the flows at takeoff and cruise and did they change? Because a huge amount of fuel in the Continental system is returned to the tank, pressure may not be a factor. And, from experience, check the cowling and other areas for blue staining and flag any aroma of avgas in the cockpit as a show stopper (those flows were actually higher than normal because of leaks).
Paul Legacy 550N Calgary On 2012-07-05, at 9:36 PM, Robert R Pastusek wrote: Alan, How about a blockage in the fuel system? I mention this because we just found a disintegrated fuel flow impeller (a wee tiny thing to start with) that was blocking the fuel line on a TSIO-550. The owner says the fuel flow was “indicating” even when the engine would barely run, so apparently there was enough impeller in the sensor to at least give a reading, but most of it was down-stream in the fuel system. (the engine did not run well at all…) Bob From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Alan Crawford
Sent: Thursday, July 05, 2012 3:45 PM
To: lml@lancaironline.net
Subject: [LML] Fuel Pressure Problems Just started having a change in fuel pressure at cruise. I have a Legacy ... 550N ... been cruising 40 to 60 degrees lean of peak with no problem, with fuel pressure above 8.2 psi. Depending on altitude 2500 rpm - 2300 rpm ... 11.5 to 11.8 gph ... The last few flights I can not get 40 degrees lean of peak at any altitude without the fuel pressure dropping below 8.0 psi ... even if I turn on the fuel pump to low = 9, 500 - 11,500 - 12,500 ???? any ideas on what is going on???? Takeoff fuel pressure is 28.0 psi ....
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