Berni,
What altitude were you flying at when the surging occurred? It was
standard procedure in my ES (w/ NA IO-550N) to turn on low boost above
10000' to avoid this problem.

Paul Bricker

On 5/15/11 5:04 AM, "Berni" <bbreen@cableone.net> 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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