Okay, so a few months back i had alot of work done on my blazer and it was running just fine. then it started having problems starting. eventually it got to the point where it was too unreliable to drive anywhere because sometimes it would start and sometimes it wouldnt. it then sat in my driveway for 2 months until i finally got around to replacing the fuel pump ( the suspected problem). Once replaced it ran fine for 2 days, then suddenly... it wont start again. it cranks and cranks and cranks but wont start. when we try to start it, the humming from the pump cannot be heard. Any ideas? Thanks in advance.

 

every engine needs 3 things to run. Fuel, Compression, spark. so start testing.

start with fuel, make sure your getting good fuel psi and the injectors are spitting okay.
then test for spark, make sure you entire ignition system is running like it should.
then go to compression. get a compression tester and make sure you have good compression on all cylinders.

if all check out fine, let me know and ill help you brain storm =]

also what work did you have done before this problem happened?

 

Since you don't hear the pump kick on then I'd start with checking the fuel pressure of your system. Autozone will lend you one for free. Hook it up and turn the key to on (past ACC but no need to crank the engine). The pump should turn on for 2 seconds and pressurize the line. if it's zero psi then your it's definitely not turning on. The pressure should read something above 50 (forgot the exact number) and hold for at least 5 minutes. That's where I'd start.

What pump did you install? I'll assume it was not a Delphi/Delco if you have no pressure. If no pressure and not an OEM there's a high percentage that the pump needs to be replaced again -- but there's troubleshooting until that comes to pass.

 

You could also just take an light tester, turn the key over and see if you are getting power first if you like.Their is the posibility that you have a fuse blown or my be a relay. Just some more suggestions. I had a dim head light, and could not figure out why? come to find out the fuse was blown but there was still current passing threw it so actually pull the fuse and look at them.