hey i have a 98 blazer and it won't start...unless i spray starting fluid in the throttle body. Once it's running it runs like a champ with no problems. Once it's shut off it won't start again without a spray. It's got a new fuel pump about 6 months ago and regulator. The pressure is at 50 psi when starting and injector pulse is fine also. It also has a new fuel filter too. I heard someone say it needs 60-65psi when starting or the injector pintles wont open. Do you think the pump is bad again?

The pressure is too low, but it may not be the pump. When was the last time that the fuel filter was changed? A weak battery could cause low intial pressure, too.

The pressure is at 50 psi when starting and injector pulse is fine also

I just recently had the same problem and solved it by replacing the fuel pump. Search on my posts, I'm not sure which one it was within the last few weeks. My static pressure would go to 60 psi but when cranking would drop to about 45 psi. I could only start by using starter fluid but then the engine would run fine. Also, make sure your battery voltage is OK, good spark, etc.

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
Post back fuel pressure readings.

MT