The basic design of the Bendix fuel injection system was done before or during WWII, so I'm surprised that the "designer" is still around.  Point is, it's been here for a long time, although the current configuration was put together in the 50's.  And it still works quite well, so I guess that says something.

Berni says that his lines are "heat shielded", but I don't know exactly what that means.  I used the loose-fitting "fire sleeve" on mine, as I felt it provided better insulation than the integral fire sleeves that are sold.  The most important fuel line is the one from the fuel servo to the distributor and it is very important that it be adequately insulated.  The first fuel to vaporize is from the distributor to the injectors, as there is nothing but an orifice at the injector to keep fuel from running out.  Then the fuel inside the distributor can vaporize, pushing the distributor valve open and pumping more fuel out through the injectors.  finally, the fuel in the line from the servo can vaporize.  All that contributes to the rich hot start problem, which occurs with either the "Bendix" or the Continental system as they are essentially the same in this area.

The problem Berni describes is after starting when the engine surges, and that is from a lean condition, either from bubbles in the fuel going through the injectors, or from a vapor lock of the pump.  So after starting there is almost no way to cure the surge, except to keep the engine running at relaively high load, which increases the fuel flow and reduces the time it takes to cool down the fuel system.  Leaving the electric pump on will usually cure a vapor lock issue, but that isn't the usual cause (in fact, some airplanes I've flown seemed to be more likely to vapor lock the electric pump than the mechanical one).  One reason to keep the engine running at a reasonably high speed it to keep it from stopping during a surge condition.  Then it is important to avoid any slow idle periods just before takeoff, as vapor can reform during periods of low fuel flow.  I suspect that was the cause of the surge during takeoff.

Just some of my thoughts that I hope help.

Gary Casey

Berni, 100 octane fuel boils at a very low temp. Fuel is boiling in the injection lines when the engine is hot when you are idling. When you are above idle there is enough fuel traversing the fuel lines to keep them under the boiling point which is why you only get this this at idle when the engine is hot. 

This was explained to me by don Rivera at airflow performance, he designed the bendix injection system and is the guy who designed the airflow performance system as well so he knows what he is talking about. This same reason is responsible for the hot start issues in our fuel injection set ups.
This is normal...
Randy Snarr 
N694RS


Sent from my iPad

On Apr 8, 2012, at 8:37 PM, Berni Breen <bbreen@cableone.net> wrote:

> Whenever my GAMI injected IO360 powered Lancair 360 is really heated up, following a flight and only a short time to cool down (less than 30 minutes) and restarted, the engine will surge during idle and taxi.  Again this only happens when the engine is hot, has been shut down and restarted.  The issue never occurs when the airplane (engine) is started for the first time on any given day (super hot day or super cold day).
> 
> Since I feel the issue is fuel related I tried leaning and use of the electronic fuel pump during idle and taxi with zero improvement.  The engine runs very badly with a pronounced surge.  If I get on the runway and give the engine full throttle, the engine will develop good power and lift off as if there were no issue...that is until yesterday when the engine just about quit 2000' into my takeoff roll.  I aborted the takeoff, did some high speed taxiing and then took off 3 minutes later (no shutdown).
> 
> Today I took off, climbed aggressively to get the engine good and hot and landed.  I shutdown, let the engine sit for about 10 minutes, restarted and once again experienced the surge during idle and or taxiing.  I removed the upper and lower cowl but am still not able to identify the cause of my issue.
> 
> Clearly I have an issue that is caused by heat affecting fuel.  All of my fuel lines are heat shielded.  Can anyone offer suggestions or ideas that I can try?
> 
> Berni