Hey, I have a 2000 2dr blazer, 4wd, replaced the fuel pump and ran fine for two weeks. Now if it sits over night I have to crank it two or three times to get it started, and sometimes while I am driving it will start to bog down, meaning it won't go above 20 or 30 mph. If I pull over & put it in neutral and rev it it's fine. But when I put it back in drive and try to give it gas it doesn't want to go. Wires, plugs, cap, rotor, fuel filter(2x), air filter, mass air flow sensor all have been replaced. The truck has 105,000 miles on it. Please help as now I am forced to use the wife's mini-van.

 

Boy, not sure but maybe I can help. I see that you have replaced the items like the fuel filter, plugs, rotor, etc. that would normally be associated with this type of behavior thought. Two questions when youreplaced the fuel pumpdid that include one of the filter changes also. Because if not you could have crap built up from when the old pump was on. If you did the onlything that jumps into my brain is Ito have had to replace my fuel pump and when I puteverything back together it started, ran ok for awhile then I started the same type of symptoms you are experiencing. After about 3 days it became undriveable (as where Ilive now if you don't have a lead foot you ares**t out of luck because they drive like moronshere).
Anyway I took it to a friend of mines (towed it) and you could here the fuel pump on it sounded normal but when we tested the fuelpreesure the pump volume was not what it should have been. So we took it off and took it back to the parts store according to the guy there are a couple of types of replacement pumps including the ones they get from GM that seen to run fine meaning when you hit the key you can hear them come on but after awhile they start to fail internally causing pressure to drop. I ask the guy wouldn't you have other motor problems he said from what they had researched and customer feed back that this typically was the only complaint and it was not uncommon to once in awhile get a bad pump. Sorry this is so long and like I said it could be just a shot in the dark. You might other stuff that is contributing but its so hard to not be there to look at it, as it is kinda hard to diagnose something you can't look atyourself. SoI am onlygoing off of my own personal experience.Good Luck to you hopethis gets you in therightdirection.

Oh, Ifeel for you on the mini van bro.

Almost forgot did you make sure the connections were clean (electrical) and hooked up securely if the pump isn't getting full power that could cause it.
How sure are you that its the engine? You said if you pull over and rev it that it seems ok. Mine did that not to long ago and I was kinda freaking and drained the trans in anticipation that the damn thing needed to be rebuit but it turned out after flushing it several times and changing the filter and cleaning out the valve body it had some crap built up it took care of the problem. I would check the fuel pump though and go from there.

 

This almost sounds like you have a clogged catalytic converter.

 

I think Kyle could also be right that could also cause your symptoms. Now I have a question. How come so many of you guys on here have had problems and had to replace your converters. I have over 155,000 miles on mine when I changed the exhaust it was inspected ( county I live in requires that anytime exhaust work is to be done that emissions must be tested and examined for good working order)(I did the exhaust work but had to take it to the shop to be welded because my welder quit) and didn't have anything wrong the truck passed emissions like it was brand new ( according to the sheet I got when it was passed). I have heard that winters and extreme high heat with humidity and short drives are death to converters but mine still passes emission with no problems and theproblems I had with mine everytime the converter was ruled out as the possible cause. I guess thats why I never think that there could be a problem with the converter, as mine has not failed yet ( yet I guess is the key word). I also run additives in mine, maybe that helps. I run a fuel injector cleaner once a month, then about every two tanks of gas I run a premix that I get from the auto parts store that has a octane boost, stabilizer and conditioner.