TBI fuel pressure regulator question

[Jay Vessels]

Hi there!

Dad rigged a fuel pressure gauge today and powered the pump.  The gauge was
connected to the fuel filter outlet such that the fuel filter was only
connected to the gauge (i.e. no return path, just pressure to the gauge).
Reading was 15.5 psi.  I assume this is enough for a TBI pump deadheading
into a gauge.

The return line from the TBI doesn't have any fuel flowing from it when the
pump is running, so Dad's going to tear into the TBI and make sure it's
okay inside.  

The real problem for me is that Dad's got the car, and his house is 90
miles away from mine, so we're having to work through some of this by phone
until I visit again.

Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
1994 Chevrolet Cavalier Z24 Conv., 3.1V6 MPI


At 03:45 PM 9/17/01 -0400, you wrote:
>
>>  Carefully Check the Fuel Cap , The Fuel Pickup , The Fuel Line
Orientation,
>      Check The Strainer @base of fuel pickup. A bone yard Pump may have spun
>      one of the plastic pump rotors. Pump internal bypass may have a
problem.
>      Watch the FP relay Voltage vs Bat Voltage. Major Irregularities [ Draw]
>      indicate a FP failure in progress, or a major restriction.
>     Double , Double Check ground connections and resistance values.
>     Something as silly as a small piece of debris in pump can make you go
>     bonkers. Anything that can go wrong usually will do so.
>     Len
>
>
>> >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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>> >
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