TBI fuel pressure regulator question

[Jay Vessels]

Hi there!

Dad and I are currently converting my cousin's '85 Caprice 305V8
Q-jet/700R4/federal emmissions to a TBI system from an '89 (305V8 TBi
1228746 ECM/700R4/Federal emmissions) and have run into an interesting
problem.

I finished modifying the '89 harness and finally got it installed today.
Dad finished plumbing the fuel lines, and we decided to check for leaks.  I
jumpered across the fuel pump relay (ECM not installed yet) to run the
pump.  We had fuel all the way to the TBI, but almost no fuel came from the
return line.  Cracking open the fuel feed line at the TBI after removing
power from the pump yielded a spray of fuel.  The return line during this
test was simply a 3/8" steel line from the TBI emptying into a small jar
(not connected to the fuel tank).  The canister vent line was unhooked to
make sure the tank was venting.

It seemed odd, but we buttoned everything up and tried to start it.  It
would spin over fine, and acted like it wanted to start but only hit once
or twice.  it would not run on its own.  Using an inductive timing light,
we verified that spark was getting to the plugs (we tried a couple, not all
8).  Shining the timing light at the injectors shows fuel is being sprayed
into the throttle bores.  We also verified that the distributor timing is
close (i.e. we don't think we're off a tooth or anything like that).

Another thing I noticed, besides the lack of fuel flowing from the return
line, is the fuel pump is LOUD.  I can hear it run quite loudly.  I can
hear the pump in all the other cars, but they're not nearly as loud as this
one.  It is a junkyard piece so I don't know it's history.  Dad is going to
get a fuel pressure gauge tomorrow.

It acts just like it's not getting fuel, but I know the injectors are
firing.  Is this a case of really low fuel pressure, or is there perhaps a
problem with the throttle body (i.e. pressure regulator)?

Any ideas are greatly appreciated.
Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
1994 Chevrolet Cavalier Z24 Conv., 3.1V6 MPI




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