I posted on the TPI board a couple of days ago and not much respons... I need to get to the bottom of this problem:

First Post:
fuel pump replaced, but still had problems. We put a guage on the fuel rail and drove it... pressure dropped to about 20 psi above 2500 rpm or when pedal was floored. Now, a new regulator, but still not holding pressure. If we pinch the return line, pressure goes up to over 80psi. Otherwise, we still see low pressure at revs. Mechanic is stumped. Is there a vacuum line to the FPR? If so, what does it do?

Then, I posted:
The shop installed a Mallory adjustable FPR. This was their answer to the dropping fuel pressure problem, after they put in a new spring & diaphram in the old FPR

They then left the original FPR alone and added the Mallory FPR to the return line. It seemed to work at first, but out on the street in was back to the same old problem... the car will not accelerate past 2500 rpm or so... sometimes it will rev to 3k. When it falls down at 2500 rpm or so, nothing will let it gain revs. If the pedal is depressed or even floored, not much seems to happen, just bogs and goes nowhere. In park or neutral, it will rev right up to 4k+, no problem, no hesitation.

I just got the car back for the weekend... it is actually drivable. I still have rented a pressure tester. I will put it back on and drive it, but I know I will see the pressure drop at aroung 2500 rpm... it drops to about 20, especially when it starts to bog... flooring it just make it worse.

One thing more... if the car is turned off, then restarted, it is better until the computer takes over... 30-40 seconds.

Can this possible have anything to do with a new transmission installed with a 4k converter?

We are all at a lose at to what is causing the fuel pressure to drop... an open injector, I guess, but would that make it bog down and fall on its face?

 

Check the fuel volume (flow).

This is like one of those tiny water lines going to the ice maker in the back of a refrigerator as opposed to a fire hose connected to the fire hydrant in your street.

Both lines would read the same water pressure from the city water pipes, but you would get a heck of a lot more water out of the fire hose! (It would have more volume.)

More...
http://www.asashop.org/autoinc/june98/techtotech.htm

 

thanks for the link... I'll study it!

my fuel lines are unchanged. We've looking for kinks or other problems. I am leaning toward the injector. I have looked and search, but have not yet found a step-by-step procedure for measuring ohms. The measurement is from one termial through to the other, I would guess. What has to come off the motor in order to gain access to all injectors?

 

You don't have to take anything off the motor to "ohm" the injectors. You just have to remove each plug by squeezing the wire retainer clip (on both sides simultaneously) and pulling up. Be careful you don't break the 20 year old connectors. You can turn the injector in it's socket to get better access to the cap if you need to, but be gentle as I suppose you could break an o-ring doing that. If you have a stock 305, you should have 19lb/hr injectors. If your fuel pressure is dropping under load, then make sure the filter is good. Like someone else said, you might have a clog/restriction somewhere in the lines. It would still build the correct pressure until you started flowing too much fuel, then the pressure would drop like you're describing.