If you indeed have a bad fuel pump chances are you'll be hes hes hesi hesitating under load.

 

So what did the open FPR tell me? As stated earlier it didn't start any easier with it open to atmosphere.

 

I really think the culprit is the FPR here.

But then again, you're talking about a mix&match of 90 and 93 ECU and AFM..
That's an entirely different plot twist.

 

Curly, you might also take a peak at the '92 FSM in the sticky. If memory serves, there are some flowcharts there that might help.

 

Curly, have you checked the grounds?
Really.
Bad grounds will cause the symptoms you are describing.

 

I'm going to hold off on that check until we verify fuel pressure and/or check again with another ECU. I'm praying for the free ECU, but replacing a $20 fuel pump isn't the worst option either.

On another note, does anyone have experience with a $20 ebay fuel pump?

 

When you say bad grounds are you referring to the grounds on the engine harness?

 

Yes. There are several ground points on/around the intake manifold.
I would also check the ground strap and battery terminals while I am at it.

Bad ground will result in very strange sensor outputs, cause motors in pumps etc to run erratically, and create unnecessary painintheassery.

 

Agree with checking/cleaning grounds. I assaulted all underhood grounds on my car with my stainless wheel equipped dremel and some dielectric grease and it was surprisingly effective. Brighter headlights and smoother idle, I kid you not.

 

I took it one step further.
Here's my ground strap: 1/2" thick, silver coated, fine strand copper wire...

 

Cleaning up your grounds sure won't hurt anything. Plus, I'll add this. If your grounds are less than ideal, the effect will be at its worst during low voltage conditions (like engine cranking).

Curly, you're in a wettish area, right?

 

Very wet. The fuel pump ground is under the soft top, under the carpet, under the metal cover. I'd be surprised if it's rusty under there. I'll look if I'm REALLY bored and nothing else helps.

 

Until you check FP you're just taking a leak in the wind, pointing up.

 

LOL. I think we're more concerned about sensor grounds than the fuel pump ground.

+1 on checking FP though.

 

Ha! So Mobius' fuel pressure gauge was apparently hiding in his compression tester box and sitting in my garage this entire time.

Fuel pressure was jumped at the diagnostic box. Gauge was T'd into the fuel rail feed line. It was slightly leaky, but more of a small drip, not a spray (aka: loosing pressure from leak).

Sitting doing nothing it was at 42.5psi.

With a clamped return line, it shot up to 65psi.

How does this sound in terms of pump health?

 

I think - and please feel free to correct me if I'm mistaken - fuel pressure is supposed to be about 45 psi with the engine running.
That means the regulator has vacuum on it, and is actually reducing the pressure.
Pressure reading with no vacuum on the regulator should be at least 10 psi higher.

Cliffs: I'm pretty convinced at this time that the culprit is the FPR.

 

Sounds logical to me.

 

Ecu did nothing, we've got a new used regulator on the way!

 

Please repeat the test in post #35 with the new FPR and post results.

 

Make up your mind.