[Gmecm] 93 CHEVY g20 VAN

[Dustin Lof]

I would test fuel pressure, it should be 9 to 14 psi,
you may have a blocked off or restricted return line,
also check vacuum at the map sensor, it must be
17-18inhg at idle, both should be checked with a gauge
using T connections, your thumb is not accurate
enough.

there is not a vacuum line or source, a tbi injector
is mounted outside of the the engine, or to say it
another way on the atmospheric pressure side of the
throttle plates so there is no need to compensate the
fuel pressure for engine vacuum, only for the pressure
changes inside of the air cleaner, if the diaphram is
ruptured, fuel will leak all over the back of the
throttle body and run down the bores


I will make an attempt to explain the need for a
vacuum line on a fuel pressure regulator in the next
paragraphs:


if the injector nozzle was inside the engine where
engine vacuum sucks fuel out of the injector, then the
fuel pressure regulator would have to adjust the fuel
pressure to engine vacuum, to maintain a constant flow
rate. 

Many late model vehicles have a returnless fuel
system, where injector pulse width is adjusted to
compensate for the effect of vacuum on the injector,
or there is a fuel pressure sensor mounted on the
throttle body and the current fed to the pump is
varied to change or maintain fuel pressure, Fords
returnless system has what looks like a fuel pressure
regulator mounted on the fuel rail but it has no
return line, it is actually a pulsator to smooth out
ripples and spikes in fuel pressure as the injectors
open and close.  the vacuum line attached to the
pulsator is only there in case the diaphram ruptures
fuel wont spray all over the engine compartment

--- Phillip Kuhn <pmkls1 at yahoo.com> wrote:

> It is throttle body, they are pretty much ALL simple
> spring and diaphragm, and I'm still thinking they
> have
> a vaccum source wether it comes from inside the
> throttle body or has a separate vaccum line.
> 
> 
> 
> 		
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