Finally rented a fuel tester gauge from Autozone.

My 88 GTA manual says fuel pressure should be 40 to 47 PSI.

After the car sat all day (24 hours) I hooked it up this morning and took an initial reading. I got 0 PSI. So it bled off in 24 hours to zero. Hmmm.

Turned key on, did not start car. PSI bumped up from 0 to 2 ( right, two) PSI.

Turned key off, on again. PSI bumped to 4. And on and on, I bumped the PSI up 2 PSI at a time, to 14. At every bump, the PSI held. I tried starting it at 14 PSI and it started right up, and slowly (about 4 seconds) moved up to 26 and held steady. No fluctuating needle at all.

Turned it off for 2 minutes. PSI held at 26.

Started again. Still 26. It went up to 28 at one point, but back down to 26.

Revving the engine doesn't changed the fuel pressure.

Bogs when I try to rev it, but I can rev it slightly.

Idled it for about 10 minutes total, and it idled fairly smoothly all the time.

I have 50,000 miles and 20 years on this fuel filter. Maybe 20 years of rust have restricted the filter?

167,000 miles total on the car. Bought the car used. Could be the original fuel pump.

Hoping it's the filter and not the fuel pump.

What are the chances my fuel filter is clogged but my fuel pump is OK ?

Thanks

 

I am going to say both may be bad, but that filter should definitely be changed first. It's not just/only rust that the filter traps, plus they are cheap and easy, comparatively, so if you change it and it doesn't solve your problem you're not out a whole lot.

 

Make sure you're testing the fuel pressure with the vacuum line disconnected from the regulator and plugged. Also did you purge the air out of the tester? Should be a bleed valve on the side to open the system and push the air or fuel out of the line. Don't discount the possibility of the loaner gauge being a bit off either.

Just change the filter anyway, then check it again. Before you drop the tank, I'd probably jump through the hoops to try another gauge, or try the gauge on a different car to verify it works right. Loaner tools take a ton of abuse.

 

Try all of what Drew said, but don't expect miracles.

Then change the filter, but don't expect miracles there either.

Most likely, a tank dropping session is in your immediate future.

 

Hey thanks for the help everyone!

I think I might have to purge the contents of the tester tube. I never did that, just screwed onto the Shrader valve and started getting readings.

I went back to the car after about 3 hours since my last post, and the pressure had gone down to 12 PSI. I tried bumping the key ON a few times but the pressure stayed at 12. I started the car and it started up on the first try, and idled OK, but it wouldn't take any gas without bogging. Hmmm. I let it idle for about 2 minutes and shut it off. The pressure never moved off of 12! Surprised it even idled at such a low pressure. Removing the vac hose to the fuel pressure regulator didn't do anything to the pressure either, or the rpm.

So... I'm going to use the relief valve on the tester to purge whatever is in the tube (air and gas?) and go from there.