Ive replaced every sensor on the motor with a new one either standard or cardone. The motor still wont run right. Ive checked all my grounds and I have a new stock fuel pump. My 383 has 32lb injectors and Is backed by a PCM for less tune. My fuel pressure sits at 40lb when its primed and 32lb when its started. The motor will only run when the mass air flow sensor is unplugged causing it to run really rich. the mass airflow sensor is brand new, i just got it today. Maybe my stock fuel pump does make enough fuel pressure causing the motor to run lean when the mass airflow sensor is plugged it. Ive been told by mechanics that 60psi and an adjustable fuel pressure regulator might solve the problem. Can anyone tell me how much fuel pressure their 383 takes to keep it running happily. what size injectors are you running.

 

I have 30# SVOs and an aeromotive FPR, i think its right around 41 for the fuel pressure. It's running a little rich, but i haven't gotten around to figuring out why.

 

Are you sure you don't have a vacumn leak somewhere? I had a problem like that once. forgot one hose felt like an --- after I found it.

 

yea they are all plugged

 

There is no reason the stock 43.5psi fuel pressure will not support the typical NA 383, as long as the injectors are large enough and the PCM is programmed for them.

All you need to do is check the fuel pressure correctly. At idle, with the vacuum compensation line removed from the FPR, you should see 43.5psi. GM accepts anything from 41-47psi, since that variation (-3%/+4%) can easilly be corrected by the closed loop long term fuel corrections.

Reconnect the vacuum line at idle, and the fuel pressure will dropp proportional to intake manifold vacuum. A stock cam might see a drop of 6-8psi. A more radical cam will see less of a drop. Tape the pressure gauge to the outside of the windshield and take it out on the road to its max HP point, and the pressure should hold within 2psi of the pressure you measured at idle with no vacuum.

That should establish whether your fuel system is healthy.

Why did you replace every sensor? Did you scan the PCM and look at how the sensors were performing under various engine operating conditions? Did you even look for codes?

If, in fact you had a faulty MAF sensor, and have now replaced it with a new one, be sure to clear the long term fuel corrections, before you try and run it. You can do that by simply pulling the "PCM BAT" fuse for 30 seconds. Running rich without the MAF (speed-density) may indicate a weak VE table in the programming. When its "running rich" what do the long term fuel corrections (BLM's) look like?

 

im new to fuel tuning and pcm programing. this is the first time i have ever experimented with a modified motor. Im not really sure of what you mean by "ve table or BLM'S"

 

The VE table is a cross refernce map that the PCM uses to determine fueling for a given point in open loop operation, or if you unplug your maf.

The BLMs are kinda like the number of correction steps from the given table number the PCM is using to try to reach what it wants to see.

I run around 43 psi fuel pressure on my car, and it spikes a little and drops slightly under WOT. (I'm using 30# SVOs).
The way I checked my fuel pressure all the way to redline was by getting a gauge that would mount to the schraeder valve and a hose long enough to tape it to my windshield in my line of site so I could see it without having to look down. (this is only when checking the FP)