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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.

Reply to
arachnid
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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?

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

Reply to
Ed M

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.

Reply to
arachnid

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[s] alerts you to.

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May be of assistance^^^^

Reply to
Knifeblade_03

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.

Reply to
arachnid

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