1991 Fifth Avenue Fuel pressure specification? (stalling problem)

I'm trying to help someone with an old 1991 Fifth Avenue (3.3L) that's
been sitting in their driveway unfixed for a year. Symptom is that it
idles OK, engine revs smoothly to high RPM's in park, accelerates to 55
mph on flat roads if you're real gentle but stalls instantly if you try
to push it at all. The engine doesn't quite die unless you keep pushing it
but it takes quite some time to recover. It can't maintain 55 on even the
slightest hill.

The fuel pump sounded awfully loud for a luxury car so I started by
replacing the fuel filter to make sure it isn't clogged. It made no
difference in the problem or the noise so I gave in and bought a
fuel-pressure gauge. Don't have my tach with me but just guessing at the
RPMS, I'm getting a fuel pressure of 30 PSI at around 1,000 RPM and 22 PSI
at around 2500 RPM. Sounds like the fuel pump to me but I'll wait for the
specs to be sure. (Just to save me a little looking, is the fuel pump on
this car in the tank or external?)

I'm also getting a TPS code which is the next suspect in line if the fuel
pump is OK. Can this code be caused by a bad fuel pump, or is it a pretty
solid indicator that I also need to pick up a TPS when I run into town for
parts?

The engine codes are:

12 Battery recently disconnected

41 Alternator field control circuit open or shorted.

24 Throttle Position Sensor

35 Cooling fan relay circuit open or shorted.

The battery was DOA from sitting for a year and I had to jump-start the
car, which may explain the alternator code. I'm holding off on the
cooling-fan problem until the car is more drivable.

 

On Thu, 03 Aug 2006 15:42:29 -0500, arachnid wrote:

Just a quick update. I let things sit for dinner and went back out to
play. I hadn't changed anything or even disconnected the fuel-pressure
gauge but fuel pressure is now staying at around 30-35PSI no matter how
high I rev the engine. It rises to 40 PSI at idle (shouldn't it drop
instead?)

The fan problem was an easy fix - I got the engine warm, started
jiggling wires, and the fan came on (probably a dirty connector from
sitting so long). It turns off and on now about as is should, but I'm
still getting the error code. How do you clear stored error codes?

 

55psi with no vacuum to the regulator, 46psi with engine idling and manifold
vacuum to the regulator.

 

Thanks. I'd planned to replace the fuel pump anyway because it's so noisy,
but that's close enough to my idle pressure that I'm not so sure now that
the fuel pump is the cause of the stalling.

Oh, well, most of the other suspects are pretty cheap.

 

Just curious, have you tried cleaning the TPS with some electrical
contact cleaner? Could be another dirt or corrosion issue. I am pretty
certain there is an idle air control motor. maybe it's sticking. Just
some thoughts.

oh, 50 on/off key cycles usually clear any codes on any new installed
components or repairs to the device that the code alerts you to.

http://tinyurl.com/qerqx

May be of assistance^^^^

 

It's pretty tightly sealed. I put an ohmmeter on the TPS and rotated the
shaft, and it seems to be in good shape. I was going to replace it anyway
since it looks like a cheap part, but the auto store wants $55. Yikes!

That's what I hate about luxury cars. Me, I drive a 22 year old Chevy S10.
Everyone has the parts in-stock and they're dirt-cheap. Also the engine
is childishly simple compared to today's technological marvels.

I was out driving around and playing with things today while waiting for
my fuel pump to come in the mail. The engine slowly lost power to
the point that I could only do about 4 mph. So I hooked up the
fuel-pressure gauge, and measured a touch under 5 PSI at idle. Aha!

Guess they wouldn't want to make life *too* easy...

Autozone never quite tells me everything I need to know. I think
they don't want to compete with their repair-manual sales.

If the car was mine I'd go buy an official factory manual. I bought a used
one for the S10 for about $120. That seems like a lot of money but it's
paid for itself *many* times over.