I have a 2003 chevy suburban 1500 Z71 with a stock 5.3 flex fuel engine.
it is real hard to start hot or cold, it just cranks and cranks.
i have to turn the ignition on and let the fuel pump prime two or three times before it will start.
i checked the fuel pressure regulator off of the fuel rail, and the diaphragm is good, it holds a vacuum as long as i let it, it dose not leak down and fuel dose not leak out when on the fuel rail.
but i did noticed that the diaphragm dose not open the valve inside, it just makes it easier to open it with a small punch manually, is that normal?

I then checked the fuel pressure with the regulator still hooked to vacuum
(i forgot to check it unhooked) and at idle and cruise it reads 42psi. and on acceleration it rises to 55psi. to 57psi.

the engine is pulling 18 to 19 in.Hg vac. at idle.

i then hooked A-tap up and read the parameters, and at idle it read as follows:
LT fuel trims
Bank 1 ( +15% )
Bank 2 ( +6% )

and on both banks the rear or # 2 O2 sensors are slow responding and do not drop below .650 they hang around .650 to .850

the MAP is at 33 to 34 Kpa

and at 2500 rpms parked it reads as follows:

LT fuel trims
Bank 1 ( +3.3% )
Bank 2 ( +1.0% )

and now the rear O2s are switching fast and going from .10 to .850

the MAP is around 24 Kpa

So, is it the fuel pump, pressure regulator, fuel injectors or something else?
any help will be appreciated.
Thanks!

 

T t t