Ok, so I have a 2000 blazer which i got about a month ago. It does not like to start after it has sat for a while. It starts rough but if you start it and turn it off and try and start it again it will start right up. So i checked my fuel pressure at idle and it is 55psi but as soon as i turn it off i will drop to zero in about 5 minutes or less. My question is would that be the fuel pressure regulator or the check valve in the pump. Also, while running if you give it gas to 3000rpm's the pressure will increase 5-8psi. is that normal?

Also my fuel pump does prime like it is suppose to when key is turned but should you be able to here it constantly while driving. It seems pretty loud for a fuel pump

 

You basically need to isolate the fuel pump from the rest of the system to determine the source of the leak. The 96+ Fuel System Diagnosis link in my signature details the testing.

Some fuel pumps are noisier than others. If it is really noisy, it likely is an aftermarket pump.

 

Yea that's what I figured. Well I isolate if I get the chance but I might just replace the fuel regulator anyway because I heard they are notorious for going out anyway. But I just got the blazer so I'm not sure if the pump as been replaced. But isn't 55psi kind of low at idle? Ive heard they run at 60/66.

 

Well i just replaced fuel pressure regulator and so far so good. But the weird thing is my pressure with key on is 60 but running it is 50/60. Is that normal I thought pressures were suppose to be 60/66?