[:-] Blazer doesn't start, fuel pump buzzes, only 35psi at fuel test port behind throttle body(fuel rail?), no codes. Could it be the fuel presure regulator under the plastic manafold? Thanks

 

Definitely sounds like the FPR, but more tests are necessary. When you had the fuel pressure gauge on the fuel line, did you monitor the fuel pressure after you turned the key off? If the fuel pressure drops after the key has been turned off, there are four possibilities - FPR, o-ring leak in CSFI spyder, fuel line leak, or leaking check valve in the pump. Most likely culprit is the FPR. Something else you could do to narrow it down is open up the throttle and smell for a strong gas smell with the pump on. If the FPR or a CSFI o-ring was leaking into the manifold, there should be a strong gas smell in the plenum - FPR should have a stronger gas smell. I suspect that with that low of a fuel pressure, that either your pump has gone or your FPR is leaking badly and dumping fuel into the intake.

If you think you've got it narrowed down to the FPR or CSFI o-ring(s), pull off the plastic upper plenum and look for a cleaned off area of the aluminum lower intake. The fuel will tend to wash off under the CSFI spyder.

 

Fuel pump. It should be pushing around 58-60psi when starting.

 

Yes, the fuel pump should be pushing 58-60psi (actually 60-65psi as per the latest specs from GM), but unless you pull the line and install a pressure gauge, you won't know if you have a weak pump or a leaky CSFI unit (o-ring or fpr). The upper plenum is easy enough to remove or atleast get part enough to see if something is leaking.

Removing the TB and using a flashlight and mirror should suffice to see well enough into the back of the upper plenum to look for drips/sprays or signs of either. This would be a lot easier than pulling the gas tank, replacing the pump only to find that you had a leaking o-ring causing the whole problem.

I'm not saying that it isn't the fuel pump, but there are other much easier and less time consuming checks that can be done to ensure that it is the pump.