Ok... Here goes... Bought this 2000 Blazer 2DR 4WD SFI w/AC 175,000 miles. Ran perfect when I bought it, 4WD didn't work and no heat; new Transfer Case and it works perfectly now. I put new plugs and wires on it and it started misfiring... New Battery and Distributor installed with cap and rotor(cause it was $25 more than C&R alone). After our first major freeze this winter, it broke down on me whilst driving and it was the ignition switch, which burnt out the blinker switch as well as a few fuses. All good for 1 day... the fuel pump went out... Replaced it with a Delco fuel pump (Cheap things aren't they?) and while I waited for it to arrive, I replaced the heater core, thermostat, fuel filter, changed the oil and cleaned the EGR valve. Fixed the heat problem. Now, after those repairs I drove the truck about 4 times and stalled out after turning the heat on at a stop sign, had to push it home by myself.
Current Problem: Gas pump primes then stops pumping gas. I checked this issue before the fuel filter, after it and at the Shradder valve on the fuel rail. I thought it was the injectors or fuel regulator. New regulator. Once the engine warms up it just stalls out, heat/ac/defrost makes it worse. Pulled it apart and CLEANED the injectors with gasoline. Still doing the same damn thing... I'm lost guys... Someone help me, please. What am I missing? I'm not a mechanic, just a handy guy(Plumber/Electronics Tinkerer), so I don't have specialty tools for engines (Except a Check Engine Reader) and would prefer to take care of the car myself. Any suggestions are appreciated.

 

If a fuel supply issue is suspected, you must start by testing the fuel pressure with a fuel pressure test gauge as defined in the fuel system diagnosis thread linked to in my signature below.

If it stalls when using vacuum powered accessories, then I would suspect a vacuum leak somewhere as well. Does everything in the HVAC system work as it should; all modes, etc?

Also, you may want to pull your EGR valve again and check it. Don't forget to use the screened gasket as it will keep chunks of carbon from potentially plugging the valve much longer than without it. While you are in there cleaning things, giving the throttle body a good cleaning wouldn't hurt anything; specifically the IAC (idle air control) valve.

 

I pulled the fuel line off. It pressurises then drops to absolutely nothing.

There was a vacuum line disconnected causing it not to run after I was working on it, I suspect I knocked it off but now it runs fine until it warms. There is one vacuum line that was plugged and taped (not by me) right by the brake booster. It comes out of some kind of check valve Tee (I'm guessing at what it is).

When I pulled the spider off I cleaned everything thoroughly. Intake/T-body/Gaskets.
Where is the IAC valve? One of the two connectors on the T-body?

When I put everything back together, I started and ran the truck for maybe 10 seconds without the egr valve on. Mine didn't have a screened gasket though, just pot metal with like cork over it.

As far as I can tell all the functions of the HVAC are functioning properly. The switch TO the defroster does seem a bit delayed however.

 

There is only a 2-3 second prime cycle when the key is turned to the 'ON' position. The pump does not run continuously until the PCM detects that the engine is turning over. This is why I stated that a gauge must be used as any other observations as to the operation of the fuel system without direct pressure measurement is not really useful given how picky these engines are about fuel pressure.

From the vacuum source connection on the engine (same fitting that the PCV vacuum hose connects to), the smaller vacuum line should run to the check valve / tee fitting. From there, one line will run into the fender to the vacuum reservoir; this is likely the line that is plugged off. The other line will run to another tee which will branch off to the 4wd system (routing depends on which system you have: 4-button auto4wd or 3-button 4wd) as well as into the firewall for the HVAC system. A leak in any of these lines typically causes high idle, but can cause a stall when coming down to idle speed under load.

The vacuum reservoir will make for higher vacuum retention allowing the various vacuum controlled accessories to work more quickly. Slow mode changes in the HVAC system is symptomatic of a missing reservoir.

The IAC valve is in the throttle body. There is a tech article showing the various 96+ SCFI engine component locations that will give exact details.

Running the engine without the EGR valve will cause a large vacuum leak and high idle if the port into the intake manifold is not plugged (detailed in the EGR cleaning tech article). Running of the engine is recommended when cleaning the EGR valve as it will allow any loose carbon buildup to be blown out of the EGR tube/port.

Screened gaskets can be picked up at most autoparts stores. The EGR cleaning tech article goes over this as well.