Need up to 30 seconds to load.
these are both fuel rails and fuel
regulators from a 1994 Runner Toyota
four-runner and one of these forerunners
had a bad regulator today I'm going to
show you how a regulator behaves when it
starts to go bad and what the symptoms
are a quick overview the regulator take
keeps the fuel system at a constant
pressure relative to the pressure
differential between the injectors and
the manifold so when you are when you're
at idle your manifold is going to be at
a higher pressure excuse me a higher
vacuum and that's going to want to suck
the fuel out of the injectors so your
effective fuel pressure is going to be
higher than the fuel pump is actually
generating at that point when you
Florida and your throttle plate is wide
open you're going to have air rushing in
you're going to have very low intake
vacuum and the at that point your fuel
pressure is going to be basically
whatever the pump is putting out if it's
unregulated and if you have a turbo in
your vehicle you're actually going to
have air that's going to be forced in
there pushing up against the injectors
which is going to lower your effective
fuel pressure so the advantage to a
return system with a manifold feedback
which these both have is that your fuel
pressure is related to the intake vacuum
or pressure so there's a diaphragm
inside each regulator and the fuel comes
up here and there's a spring and this
vacuum works with the spring to help
control the amount of flow which is sent
through this return line back to your
fuel tank they're phasing these out
these days because the hot fuel causes
more emissions but that's neither here
nor there so if i hook this up to a good
regulator with the diaphragm intact
pump it up to manifold vacuum and you
can see that gage is holding pretty
steady so that means that my diaphragm
is behaving as it should fuel is going
to you know be controlled by the
manifold vacuum on this one the
diaphragm has been eaten away by
probably by some fuel additive you pump
I pump that up and you can see that it
drops right back down as quickly as it
puppet so that means that I'm going to
not only have a situation where the fuel
the the manifold vacuum is not helping
to regulate the fuel pressure as it
should but I could potentially also have
fuel coming through my vacuum line into
the intake and throwing my mix off even
further that way so it's sort of a
double whammy there so if you can also
test these when they're on the vehicle
and if I pump you know if I put a vacuum
line up to this and if if it's leaking I
need to watch out to make sure of course
that I don't get fuel it comes back into
my vacuum gauge which would hurt it but
you know I will be able to hear feedback
from the engine as I pump this the it
will you know it'll change the idle and
if I mean you can do a sort of a crude
check with the same thing if you pinch
off this vacuum line and disconnect it
when the vehicle is running you'll be
able to hear a change in idle sort of a
crude test but it'll give you an idea if
you know your regulator is working at
all
so yeah there you have it and you know
unfortunately one one of these goes you
cannot really service it you're just
gonna suck it up and buy a new one
