TBI fuel pressure regulator question

[Toby Corkindale]

Pumps can get noisy when they're cavitating from lack of liquid to pump.
Right?

Perhaps you could check the inlet to the pump - see that its not leaking air
in somewhere, or alternatively that it isn't blocked up and restricting the
flow?

Is your fuel source higher up than the initial pump? I think some systems
don't actually suck the fuel terribly well, and rely on gravity to actually
get the fuel into the pump to start with.. it's worth a shot, anyway - try
sticking your fuel source (bucket? tank?) on top of something, with the pump
underneath, see if that helps?

-Toby
'73 toyota corona (1.6l s4 carby and very slow)
'77 bmw 320i (2.0l s4 mechanical fuel injection)
'90 VN commodore (s/c 3.8l v6 map/pfi)

On Sun, 16 Sep 2001, Jay Vessels wrote:

> 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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