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Did you verify the fuel vents are working properly? ....and that the check valves on the vents are oriented correctly?
Also - what were the ambient temperatures?
Another more far out issue: Is there a heat source in the engine compartment aimed at any fuel lines? e.g. on my IV-P if the joints on the transfer tube leak, the gascolator and associated plumbing get the heat. (Although I now have wrapped them in heat resistant covering).
On May 15, 2011, at 8:04 AM, Berni wrote:
> I have been trying to chase down the cause of a fuel issue in my normally aspirated Lancair IV engine. During a cross country flight my fuel flow indicator began to show fluctuations which I mistakenly believed to be false readings. Shortly thereafter during the same flight the engine began surging, slightly at first but increasingly worse in short time. So much so that I began to plan for an emergency landing as I was looking to find the cause and to introduce a remedy. I turned on my electric (back up) fuel pump and the engine immediately began to run strong and the fluctuation readings stabilized.
>
> After gaining altitude I turned off the electric pump and the unstable fuel flow readings as well as the engine surge returned.
>
> My initial take was that my problem was caused by a failing engine driven fuel pump. Even with that belief (once back on the ground) I checked as much of the fuel system as possible looking for potential restrictions. I looked at and cleaned the screens at the wing root connections as well as the inlet on the GAMI injectors. I found no restrictions so I removed and exchanged my engine driven pump for a rebuilt unit.
>
> After installing the rebuilt pump the engine tested fine on the ground and fine in the air on a subsequent cross country trip. Approximately 2.1 hours of flying time later the exact same symptoms returned...erratic fuel flow readings followed closely by engine surge.
>
> I am now at a loss as to what I should now look for. Could my problem be due to air somehow being introduced into my fuel flow? Should I be looking at my fuel selector as a possible culprit? If so how would I test that possibility?
>
> Any and all suggestions would be most appreciated.
>
> Sent from my iPad
> Berni Breen
> Bbreen@cableone.net
> --
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