I have a 2004 chevy blazer, that will crank but not start. Before it didn't start it felt like i would lose power at certain rpm's while driving. I put all new spark plugs and a new fuel filter into it. I put an old spark plug into spark plug wire and turned they key and it did spark. The fuel pump runs several seconds before it started. I do not have a fuel pressure tester but when i push the valve in the testing port it does spray out, and when i try to start it smells like fuel. Im have no clue what the problem might be, and was hoping someone could help.

 

Spark needs to be blue, not orange, and it needs to jump a half inch gap to ground, at each plug wire while cranking. Fuel pressure is critical on these engines. Just because it sprays out of the service port, doesn't mean it's good, so you really need to check it with a gauge. If it's just a couple of psi below spec, it might not start. Key on, engine off, fuel pump running, pressure needs to be 60psi to 66psi. https://blazerforum.com/forum/2nd-ge...eakdown-88305/ Post all 4 readings and we can help you analyze them.

 

So I checked the spark and it was blue or white, however between sparks it had a smaller spark; I am not sure if this is normal. After this I also took a spray bottle of gas and sprayed it into the intake while someone turned the key, and it fired right up. It also kept running and ran, and runs fine for now but it misses every now and then at exactly 2300 rpm. While it is running I dont know what was wrong with it or why i quit running.

 

I would suggest installing an AC Delco distributor cap & rotor, and a set of good spark plug wires, along with checking the fuel delivery system: https://blazerforum.com/forum/2nd-ge...eakdown-88305/