I have been working on this for a friend. It started with leaking fuel tank and lines.
we replaced all with new tank and pump assembly. After changing this out the truck start very hard like it is flooding blow dark carbon exhaust if you rev to 3000 it will clear until it idles and starts to load up. I tested the pressure regulator because I thought it was over pressuring. But it tested within the 85 to 90 psi as listed for this year vortec. I also replaced the rod because we had no signal. But know it is in spec. This the list of issue

Fuel gauge will not work
black smoke at idle
does not want to start turns over normal no hesitation

Parts replaced over the last year
new transmission. This is when the gas gauge stopped work I did not change for him
Complete tuneup plugs wires cap rotor pcv fuel filter air filter this week
Tps. Sensor yesterday

After reset codes starting continued to be problem but stop smoking and ran fine till today. I have not had a chance to check codes but it is. Doing the same hard to start and runs rough from a stop.

At a lost need help

 

85-90 psi is way too high and even too high for the pump to be able to produce. The highest dead head pressure I have seen one of these pumps go to is 68psi. The CPI & SCFI injection systems in these trucks requires 55-60psi for proper operation.

How is the output from the upstream O2 sensors? Do they show rich? How about the LTFT/STFT (Long/Short Term Fuel Trim) values?

 

There is no error codes for the o2s. According to the techII gm scanner I was able to borrow they are reading in spec. So is the mass airflow sensor.only codes we have had was random cylinder. Misfire and no Tps signal. I check yesterday and random cyllinder missfire.

 

What are the LTFT/STFT values as stated by the Tech2?