Okay I have been searching around for this problem for over a month with no results. So far this site has had the best info that I could find so I am hoping you guys can help me out. I have been having running issues for a while it started out as a stutter when you hit the gas, I figured it was just one of the knock sensors malfunctioning and sure enough one was unplugged so I plugged it back in and it is still stuttering. Okay so I just stay off the gas simple enough. Well then it started getting worse and worse to where it would do it going down the road and then the it quit running at all. So I checked the basics I found it had spark but it didn't have any fuel pressure. I got it towed home and found out the pump wasn't running so I went to napa and got a dephi fuel pump and new wiring harness and installed it. Fired up the blazer and went for a test drive same thing it started running badly almost right away. So I pulled the plugs four out of six were gas fouled. I dried them out and Tried it again, fires right up and ran great until you hit the gas then it immediately starts running worse and worse. I pulled the plugs again, gas fouled again cleaned them again. Then later I tried moving it and it wouldn't start so u gave it a shot of ether still nothing so I checked and sure enough no spark. So I do some research and I come up with ignition control module so I get a new one (napa Ecklin) and a new coil just in case. I change both out and new cap, rotor, and plugs are just a month old. Then it had spark and ran for a bit then started running rough as soon as you step on the gas.
I don't have gas in the oil like a bad fuel pressure regulator might do. I haven't checked fuel pressure yet but I don't think that is a problem. There is no codes for the engine no cel when running. I haven't pulled the top off of the intake yet to see if the problem is in there yet. I cannot find a MAF sensor on this engine yet. I was thinking it is wires but wouldn't the computer be able to pick up on multiple cylinder miss fires?
Please any help is appreciated I am fairly good with TBI and MPFI but this is just frustrating me badly.

 

Open up the upper intake and see all the gold washed area. I will eat my eorkboot in your nut kits not leaking... Look up CPI SPIDER LEAK on here and find your diagnosis instructions. FYI, you may as well buy an intake gasket set as you have to pull the intake off to change the nut kit (unless you have a body lift).

MAF sensors weren't used till OBD2

Your fuel pressure should be 58 with key on, 58+ starting and running, and 50+ ten min after shutdown.
NUT KIT is about 50bux
Felpro intake gasket kit will be about 39

 

I think the nut kit you are talking about is where the fuel lines connect to the spider correct? If so I had a neighbor that had that exact problem but unlike him my gas mileage has been 25mpg the whole time and there is no gas in the oil. I did drive it quite a while before it got bad.

 

The gas can be sucked into the engine instead of dripping into the oil... It depends where the leak is on the lines. You did have fouled plugs afterall. take off the VORTEC plate on top, and remove that black puck like thing and have a look inside the engine with a flashlight. If you see any gold anywhere, there is a leak. It should be jet black everywhere inside this upper plenum.

 

Okay that explains some things, I think this could be the reason for the multiple vacuum leaks that it had when I first got it. The p.o probably figured out he had a leaky spider and just put so much of a vacuum leak to it that it would run good enough to get it sold. I bet you are right, I will check this as soon as I can. Thank you

 

Update: okay finally got around to checking fuel pressure the highest reading I got was 38 but it was mostly 13 between this and the fouled plugs. I would say you are right it's probably leaking to fast to build up pressure or its a bad FPR either way it's time to pull the top off the intake will post updates as I get them.

 

Okay it's fixed, it was the fuel pressure regulator.