I am not an engineer but does anyone know why the fuel pressure regulator
 on a car engine is

 installed at or close to the fuel rail?


 Wouldn't it be easier to pressurize the fuel rail like they pressurize any
 hydraulic system, with the pressure regulator installed right at the pump?
 That way we would not need a fuel return line?

 I appreciate your comments. Thanks.


 Ramon

 It has to do with the return line system. Fuel is constantly recirculated
 to keep it cool I think. Keeps the air bubbles out which would cause a
 miss.

 Paul Lamar


In that same vane, I have heard that the reason I have to drop the whole
#@%$##%%#@!!$## fuel tank off the car to change a fuel pump is because of
vapor lock prevention.  So, instead of just changing an inline pump, I've
had to drop tanks to make the changed. What a pain on a Suburban with a big
shield and 40 gal tank.  Anyway, the comments on the fuel system in the
other chain of emails mentioned putting the fuel pumps on the outside of the
tanks for ease of replacement.  Great idea but what about the vapor lock
issue.  Is it not a problem in rotaries?  Is the whole "intank pump to
prevent vapor lock" just a myth?

Van Vannoy

Saves money as there is no reason to build a self priming pump.
Any old centrifugal pump will work.
It also cools a cheaper electric motor. Cars are all about pennies saved.

Paul Lamar


The reason that the regulator is at the fuel rail is that most of them are
vacuum corrected for accuracy and the long line to the tank would cause a
lag in response. Witness the trouble getting a clean vacuum signal on many
rotary installations. The same goes for pressure. I know the whole thing
about an incompressible fluid and all but most of the injectors are open for
milliseconds so the time it takes for pressure to change in the entire line
is important. I doubt it would be as critical on an aircraft, but the system
was designed for cars of course.
Bill Jepson