I have a 95 4.3l LS blazer that wont start. I've changed the fuel pump and fuel filter (at different times). each time i changed those parts it would start for a few days no problem then quit again. I have spark and the fuel psi is where it needs to be. The starter IS engaging. I've sprayed starting fluid in the MAS and it tries to kick over but wont. I am also not getting any trouble codes. I'm about to change out the injectors but its a spider style system and it aint cheap. any other suggestions?????

 

though you have spark and fuel pressure are you sure the gas is good in it. I know you say it ran for a few days with no problem, but maybe there is water in the fuel?

 

Rent a fuel pressure gauge from autozone. Key on should be around 60 psi and not leakdown for approx. 10 minutes. Post back the key on, engine OFF numbers and any leakdown you have.

You can also look down the passenger side of the throttle body. If its really clean looking or showing signs of washing then you know the injectors or fuel pressure regulator is leaking.

 

Just thought do you have a aftermarket security system. You said you have PSI is it because you used a fuel pressure Gage or like 50lb_cat says that you need to go rent or buy one to use.
My 96 had a similar problem along with a p1440 code. Separate from the no start and it was the center of the distributor cap. The carbon button was worn out and It was driving me crazy.
It was worse when it was wet and this is what happened









She loaded it up with fuel and killed the battery trying to start it. Charged the battery and when it started it was like a full auto machine gun going off. Then one big bang and the muffler blew apart. Believe it or not she was able to drive it home. Missing and very high RPM at idle.
When I went and checked it, not only did I find the muffler like that, but it blew the MAP sensor out of the manifold just enough to seal when she gave it gas. Then it popped out enough to give it a vacuum leak for the high rpm at idle.
Has I am looking I see the distributor cap is loose. I check and it blew so hard that the hold down tab for the screw blew off and some how cracked the end.

So I put a new muffler and tail pipe on with a MAP sensor and a distributor with cap and rotor. Mind you I already put a purge valve in it for the 1440 and 1441 code. Then a week later my daughter just had an accident and it is now going to be parted out.

 

psi is 62 with no bleed down for about 8 min. this may sound odd but it took the air intake tube off and now itll start with starting fluid only. put the intake tube back in with a new filter and now it only starts with the fluid. No rough idle or crazy rpms. once it starts it runs great.

sorry it took me a while to get back its been raining like crazy for the past week or so here in florida and i havent had a dry day until yesterday.

 

So doesn't sound like a fuel issue. You have spark but is it good spark? Have you tested the coil and each plug wire? What color is the spark?