2002 GMC 4.3L vortec V-6 with throttle body CPI. Was only pushing 20psi fuel pressure, no start. Replaced fuel pump now pushing 60psi with key on & pump running, drops to 52psi when pump shuts off. Will start & run in park, a little rough, runs at 52-54psi. No power & wants to stall in gear. Specs call for 60-66psi. Replaced all retainers on plastic flex lines.
Any Ideas?

 

sound like a injector is stuck open

 

Thanks for the input. Will take a look at that when I get off of work today.

 

When was the last time you cleaned the throttle body? Those envoys and tb's you need to clean them out every 20k miles. Buy some throttle cleaner and take off the throttle body make sure you clean it inside and out.

 

If there is less than specified fuel pressure, and you know your fuel pump is new and not an option, you can continue from there:
Check the fuel lines for leaks. Pressure leaks will be evident. Check for vacuum leaks in the fuel system (anywhere pre-pump), crushed/blocked fuel lines, and a plugged fuel pump sock/screen. Replace the fuel filter, then try your fuel pressure regulator. Very rarely does a fuel injector limit fuel pressure unless it's stuck open, but then you will be able to notice excessive unburnt fuel in the exhaust, especially since it will start and run.

 

These trucks are very sensitive when it comes to electronics. The first thing I would do is clean the TB inside and out if that doesnt do it, it could possibly be a bad ecu.

Here is a very good forum to list your problem Trailvoy.com - The Chevy Trailblazer and GMC Envoy Enthusiast Site theres a guy named Roadie he knows envoys and tb's like no tomorrow. PM him if you cant figure it out.

 

I'm pretty sure he doesn't have an Envoy or Trailblazer. In his first post he states that it is a 4.3L V-6, Envoys and Trailblazers have either a 4.2L I-6, or a 5.3L V-8.Is it throwing any check engine codes? These have been known for condensation building up on the AC lines and dripping down onto the distributor.

 

Check the vacuum line coming out of the fuel pressure regulator to see if it has fuel coming out of it. I have seem those diaphragms tear and allow fuel to get into the vacuum source. If the injectors need to be serviced we can take care of that for you @ Boost Lab.

http://www.youtube.com/watch?v=hT2-DZ-hcrA

 

Gotricebih is right, every 6 months or so I have to replace the distributor. AC lines are right over the distrubutor. There is no vacuum line coming out of the fuel pressure regulator it's internal. There's is a vacuum plug on it but it's not used. Just bought one last night and that's my next step to change. If that doesn't work I'll look at the ecu. It's a GMC sierra pick up. Thanks for all the feedback.

 

^get a piece of foam hose and put it on the line. should take care of the condensation dripping onto the distributor.