I have a 2003 chevy Silverado with the 4.3L somedays it will start and somedays it will only turn over but not fire I have replace cap, rotor, plugs, and plug wires I have spark and fuel pressure I have injector pulse but it still wont fire, I have also replaced the crank sensor I have no idea what is causing this but when it don't start if I let it sit for a day then it will start and run fine for about a month or two then it will happen again. any ideas?

 

When you are having a problem with starting it, spray some starting fluid down the throttle body. If it runs for a few seconds then your problem is fuel related.

 

tried it wont start then either thanks tho