okey I have read this on many occasion from all over but no one has shared the problem yet.
I have a 2002 blazer 4 door 2 wd.
I tried posting on here 2 years ago along with someone elses thread seeing as he had the exact same problem but never got a reply I have been having this same probem for coming up to two years now and am almost ready to sell the truck so any help would be appretiated.
here is the problem as long as there is a half a tank of gas or more there is not a problem at all.
once I get below half a tank it starts to die at stop signs red lights etc.
when it gets to a 1/4 of a tank it is twice as bad it never through a code at all up till about 2 months ago which I would not think is related to this problem seeing as these just came up over a year after the initial problem.
the codes are showing both o2 sensors and maf which I am replacing next week.
My fuel pump gets good pressure with key on it prime fine exept for on colder days it seems like it is not getting the pressure like it should when its colder out or when the truck has sat for about 2 days during the winter months what it does it will start fine but all day as long as it is within about 6 hours when my wife takes it to work she works 9 hour shifts when she goes to leave it will not start it will turn over and over till she kill the battery.
this model blazer does not have an egr valve that was the first thing I was told to check.
then fuel filter changed that no help.
then tune up no help.
I want to fix this truck but I have seen people dump thousand to find this problem and still have not I took it to a gm dealer let them hear it the mechanic tells me that he has seen one other do this and they don't even know how to fix it.
which worries me.

 

You might have fun reading through this thread. It is very similar to your problem and mine. And man are you right about people never following through with their posts.
here ya go:
https://blazerforum.com/forum/showth...t=47829&page=2

 

that talk alot on the egr mine don't have a egr on it i am almost to a point of thinking there might be a pinhole in the fuel pickup my grandfather told me it is rare but he has seen it and it does the same thing that I describe.
like I said truck runs normal when it is above half a tank like there is nothing wrong with it other than the radiator fan staying on all the time but I am assuming that is because I live in tx. lol.

 

An easy test would be to see how much vaccuum your engine has. Generally you want around 17 in Hg. They sell vaccuum gauges at most auto parts stores for cheap. Also if it's having problems with the gas tank being at 1/2 I would have dropped the tank first before moving on. Just my two cents though, they put screen socks on some fuel pumps when they instal them. if this screen is plugged on the bottom but not the top, that could also do it. Meaning when the truck is above half full it's sucking through the top of the screen. Also is your fuel gauge accurate? GM's are notorious for their fuel guage sending unit to go bad or become off, maybe you have less fuel then you think.

 

fuel gauge still works properly as far as normal conditions the only differnce I have notice with the gauge is when I am at a 1/4 of a tank and the truck stalls out at a stop light and I start it back up it will then show 1/2 a tank until I drive about 20 feet then it goes back down to a 1/4 of a tank like it was.
I will pull the tank off first then I was unaware of the being something over the pickup line can you purchase these seperatly.
I know it is going to be a week or so before I can touch it tank is full right now and have to wait till a check clears to fix this problem.
I'll let you know what I find out on the sock I will also do a vac test once I learn how to lol not something I have ever done