I own a 2001 Blazer 4.3lt 4 door 4 wheel drive. I was having a hard starting problem it would take several attempts to start before it would run. On a few occasions it would back fire through the intake manifold. Researching pointed to the fuel pressure regulator. Put fuel pressure gauge on key on engine off got 55 to 60 psi it would drop to 48 or so. Changed fuel regulator (inside intake manifold) Inside the manifold it was pretty carbonized except under the regulator so I thought this was most probably the problem. When everything was back together I had no fuel pressure. Even though I could hear the fuel pump with the key on. I thought since the pump was on the old side maybe I could hear it but it wasn't pumping. I dropped the tank and changed the pump and fuel filter. Put pressure gauge back on and no pressure (0psi). I can hear the relay click and the pump. What did I overlook
just changed the fuel pressure regulator on my 1996 Silverado. The truck would not start after all the work. I took it apart the next day and found the smallest o-ring damaged. I am sure it happened when i pushed the regulator into the "spider" fuel ejector pack. (Really dislike this system). Anyway, I noticed a small piece missing from the O-ring which was still in the ejector pack. After I removed the piece of O-ring I figured out what caused this. I put the O-ring into the ejector pack and pushed the regulator into it. A better way is to put the larger O-ring on, the small filter and then the smallest O-ring on the regulator, put a small amount of oil on the O-rings and press it into the ejector pack. I connected the fuel lines and checked for pressure on the shrader valve which was good to go. Then put it all back together 'again ' and it started up with no problem. The truck ran prior to me working on it so I knew I caused the issue. A word of advice: if you work on something and it acts differently than when you first worked on it, always suspect what was done last. Hope this helps someone.