Bill Freeman wrote:

At 09:23 PM 6/27/00 -0700, you wrote:

Mike Wills wrote:

Paul,

  I know how much you enjoy knocking the S-51.    :-)

  In this case you can't blame the Chevy anyway. This came from an RV-list
discussion of fuel injection return lines. Previous poster suggested
returning the fuel to a T in the fuel supply line.

Mike Wills

   I would strongly suggest that you return all fuel to the tank that you

have

selected. a six port valve will do this. A recent crash of a Stewart S51,
with  Air performence injection, has been traced to a instilation where
return fuel was  teed back in up stream of the selecter valve. Post crash
runing of the motor with the with the fuel lines instrumented showed that
after a ten minute cruse rpm run the temperature of the fuel at the input to
the injectors was well above the boiling point. The motor  vaper locked and
quit.  This test was repeated with the same results. Return lines to the
tanks adds weight and complexity but in my opinion will be well worth the
time and effort. Even with fire sleveing there is a LOT of heat conducted
into the fuel by the fuel pump and associated accesserys. Cool Fuel from
the tanks will go a long way in eliminating this problem. I realise your
concern is starting but remember that there is a lot of excess fuel
returned in a injected motor during normal operation.

Don McShurley
Stewart S-51 N514BM

I beleive this fits with my recommendation to avoid setting return fuel to
the sump.  Back to a big tank that can dump the heat.  Sounds like the
pump in this case was extremely overcapacity, which makes the problem
worse.  Hope the folks that were pushing the 'return to header/sump tank'
design are paying attention.

Bill

 
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