Ford Explorer: Revised question check valve @ fuel pump

That the pressure bleeds off indicates the presence of "faulty" parts......
if the pressure bleeds off yet remains within spec, we deduce that the parts
aren't "faulty enough" to replace since we are likely seeing no running
problems created by this. No fuel is supposed to leak from the system - but
there is an allowable amount of pressure drop before it becomes a running
concern.

The whole purpose of the system (when it is shut off) is to maintain
pressure in the fuel rail, this keeps the fuel from vapourizing and also
keeps air from infiltrating the fuel rail. When we first turn the key to the
run position, we hear the fuel pump run for about 1.5 seconds to ensure that
the fuel rail is at the proper "static" pressure. By "static" pressure, I
mean the regulated fuel pressure when the FPR "sees" atmospheric pressure at
the diaphragm (a bit more on this later).

Fuel can drain from the pressure side of the fuel system at any number of
literally dozens of places... the fuel pump, the regulator (both past the
control valve or past the diaphragm), the injectors themselves or any one of
the myriad external connections - some leaks slow enough that any
tattletales might evaporate before they ever become evident. Naturally, any
external fuel leaks should be serviced since they will be a safety concern
before they are a running concern.

Back to that pesky fuel pressure regulator...... the orofice at the tip of
the fuel injector gives its optimum spray pattern at a particular pressure
drop across the orofice (got to be careful since we could enter the zone
where we need to reconcile manifold vacuum and manifold absolute pressure -
two totally different ways of expressing the same thing). Anyway, when
manifold vacuum is high, the FPR "sees" this high vacuum at the diaphragm
and reduces the rail pressure to maintain the desired pressure drop across
the injector tip - resulting in the optimum injector spray pattern. When
driving conditions drop the manifold vacuum (i.e., manifold pressure
approaches atmospheric pressure), the FPR diaphragm responds by increasing
the fuel pressure, again maintaining the ideal pressure drop across the
injector tip

HTH


--
Jim Warman
net



"Sonny" <com> wrote in message
news:tZ4gb.101$uswest.net... 
siphoning 
5 
faulty