Alright, got an 89 Chevy k1500. 1. Put a fuel pressure gauge in the fuel line right before it goes into the TBI unit. 2. Modified the fuel pressure regulator as instructed here http://www.thirdgen.org/newdesign/tech/tbi-afpr.shtml. Turned it so it was as open as it can get. 3. Installed a Walbro 190 liter per minute in-tank fuel pump. Pressure gauge shows 13 PSI fuel pressure. Hooked a laptop to the computer through an ALDL cable and it shows that the motor is running lean. How do I get more fuel in there? I would think that I could get more pressure than 13 psi with that 190 ltr fuel pump. Ideas?

Stick a washer between the spring and the little plunger deal as that will shim the spring to make it harder therefore more fuel pressure.

Thats a good idea, has anyone else tried this and seen the same results? Wonder what kind of pressure I can expect...

With 2 washers I can get my factory regulator from 15 psi stock to 21. I am using a TPI pump though.

Are you sure it isn't a 190 liter per HOUR pump
Did you get the generic pump or a TBI specific?
Also, when you say all the way open I hope you don't mean all the way backed out. Screw the screw in to increase pressure. I don't think you can get more than 20psi with the stock regulator and spring before the coils bind. I had to replace my holley spring with some generic beefy "valve" spring to get my pressure up above 20, infact it was stopping at 18psi and then jumping up to 40 (coil bind).
Washers work but you can also replace the spring with a stronger one from the 94-95 TBI vehicles.

You're right, 190 ltr per hour. The pump I got was Walbro Part Number FPG001

When you turn the screw counter clockwise it pushes the platform downward, which then compresses the spring. Thats where I've got it maxed out. It is as far downwards (turned counter clockwise) that I can get it.

Is this corrent? I guess the next step is a couple washers, then if that doesn't give me the pressure I need I'll look into a new spring.

Nope, wrong way. Clockwise compresses the spring. The spring is imbetween the "platform" and the pressure diaphragm so screwing in the screw will increase the pressure. As it sits, you're min fuel pressure is caused by the small return line size compared to supply. This happens with larger fuel pumps but it's just one more reason to increase the fuel pressure and start messing with the chip.

topdown solutions has a slightly stiffer spring for us. 1995-1996 was for 36 lbs FP per turbo city(45 lb injectors in 7.4L). i happen to have a 1995-1996 spring in my tool box? anyone need?

Let's think about this before I go tearing into my TBI unit again. I am pretty sure I had it right, but can't be 100% as I'm questioning it now. When you turn the screw clockwise (inwards) the platform will move up the screw, just like tightening a nut would, moving towards the head of the screw. So that would mean the more you screw it in, the higher the platform goes on the screw, the more room the spring has, the less compressed it is. Resulting in less pressure on the diaphram and less fuel pressure.

Do i have it right or wrong?

this is fun. depends if you are on top or bottom. i will assume you are looking from bottom up. i say turning the screw places the "nut" closer to head of bolt and FP decreases. less tension on spring. BUT i suspect JP is looking top to bottom. so counterclock is decreasing FP. clockwise in increasing. depends on your point of view. i guessed on weekend and FP gauge showed i was upping FP.

I am flipping the fuel pressure regulator upside down, so the diaphram is at the bottom and the head of the screw is at the top. Otherwise I would be holding it above my head with the screwdriver pointing towards the sky. Doesn't make sense to do it like that.

It doesn't matter how you're holding the regulator, clockwise is clockwise, counter is counter. I think you aren't understanding WHERE the spring is inside the regulator. From your description it sounds like you believe the spring to be imbetween the "can" and the platform. It isn't there, it's imbetween the platform (that moves up and down inside the can) and the diaphram. So clockwise on the screw will compress the spring, counter (or "out") uncompresses the spring reducing pressure.

Maybe this will help him. As you screw in the adjuster you will compress the spring into that round housing.

This is driving me crazy. That platform has a tab that sticks out as you can see from the picture. As you turn the screw clockwise that notch moves up (as the unit sits in the picture). Just like a NUT would if it was on the screw. So the platform moves away from the diaphram. The spring uncompresses.

If you screw it counter clockwise it would be like loosening a nut and it would move down in the picture, until it eventually came off the screw. When that tab goes down, it puts more pressure on the spring and it compresses.

Here are the directions

"Step Ten: Now that you have drilled out the cap you will find that the screw and platform inside the cup are not only movable but removable from the cup. By turning the screw counter clockwise you raise the platform thus raising fuel pressure. You can raise the platform to a higher pressure and put it back together at this point but that takes away some of the adjustability to it. "

Arguements?

See the little tab on the side. When it is all the way up toward the top of the injector pad, you are at max psi.

And to get the tab to that position you have to turn the screw counter clockwise!

IIRC yep. The plate won't turn the screw stays in the same place just slides the plate up and down. Turning the screw counter clockwise backs the plate off the screw and moves the plate up. That increases the pressure the diaphram has to overcome and increases the fuel pressure.

i told you this would be fun.

So I was right from the beginning.

So the solution to get more fuel pressure is to add a washer or get a stiffer spring right?

i dont understand why you cant get over 13 lbs with stock spring? if stock FP is 11-13 it would seem plausible 15 is doable? top down solutions charges like $15 for spring. since it is apart i would give that a try.

So in theory, with a 190 lph fuel pump and the regulator as compressed as it can get, I should be getting more than 13psi right? Wonder why I'm not...

not sure is this is aplicable BUT 'search" for return line issues. not sure what too small RL for your size pump will do to FP? i have stock 350 RL with TPI pump and am at 16.5 lbs today.