Hello I'm new to the site and it looks like I may able to find some help here.
I have a 2004 Blazer 4wd(not the trailblazer)2004 Chevrolet Truck Blazer 4WD 4.3L SFI OHV 6cyl...I had a no start the other day and trying to figure what the problem may be.It seemed to have slwer starts a few times off an on.Never had a problem when driving up inclines/hills,no bucking etc.I am thinking fuel pump and the only reason is that I hear no hum when key turned.I'm tyring to borrow a fuel pruessure tester If I can catch the guy that may have one.I'm guessing this may be an easy diag.Is there anything I should check for(simple things) in the meanwhile.
I have put a few gallons of fuel in it to make sure,since the fuel gauge has always lied.It would read 1/4 tank but be less.I am parked on a slight incline in driveway so it should have at least 5 gal in it.
I swaped the horn relay with the Fuel pump relay fuse to test .No difference.
Checked to make sure it was fully in gear when trying to start and also tried in nuetral.
What the easiest way to check for spark?--I believe I can take a plug wire out--stick in a screwdriver and place close to a ground and have someone crank to see if there is one.These plugs and wires seem like a challenge to get at and change.
Any other fuses to check ?I read something about ECM B?Can I swap a fuse of similar amp and try that?
I'm at a loss right now and trying to get Ideas.Thanks

 

You are on the right track, you do need the gage. While you wait you can jump the prime terminal to help rule out other electrical problems. I think this is Captain Hooks pic. Put 12v to the terminal and the pump should run.

 

I got around to doing the quick tese on that Primer connection as in photo--still no pump buzz..I guess I wouldn't have to worry about testing the spark plug for spark in this case,I imagine.Still trying to catch my neighbor for the fuel pump tester---I know I can rent onee at an autozone--but I don't even have the money for that for 2 weeks.I put a paper clip in there with some copper speaker wire I has laying around and connected to + battery terminal.Also had a battery jumper connected to battery thinking I would get the max volts.
So nothing on the primer...anything else worth a shot?

 

if you checked the relay and its good, and you still don't hear a buzz when you turn the key forward, its more than likely your fuel pump man.

Ive done that to 5 different s10's and it was the fuel pump everytime, ****tiest fuel pump ever made for a vehicle.

 

You can see if you have 12v at the fuel pump when the pump prime is jumped. It will be the gray wire at the pump. The black ground wire should have less then 5 ohms resistance for a good ground. The ppl and the white with black stripe should be for your fuel gage. At this point don't worry about those.
If you have 12v at the gray and a good ground the pump should run.