You need 3 things.
Compression
Good hot blue spark to all plugs.
Good gasoline and proper fuel pressure. 63-64 lbs.
If you have all 3 then move on to injector pulse to all injectors.
You may be weak on fuel pressure . even a couple of lbs low on a cold start will cause a no start. Double check cold start cranking fuel pressure. If under 63-62 lbs you have problems. One test is to give it a squirt of carb cleaner not starting fluid. If it starts then you have a fuel pressure problem. Run the full fuel pressure test and post back pressures. Here is the guide lines on testing.
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.
Also you mentioned that you replaced the fuel pump, it's common for the $15.00 wire harness from the fuel pump to the frame will break and there is a bad connection till the wires heat up. You can try this trick, turn your ignition on for 30 seconds "engine not running" and then turn it off for for 5 seconds and then try to start. This will energize the fuel line if the fuel line check valve is bad which is a part of the fuel pump and will heat up the wire harness which will make a better connection and see if the engine starts easier. Regardless, inspect the wire harness for corrosion and the ground is good. Good luck and keep me posted.
Testimonial: "Gosh, thanks for all the input, i'll check all you sent. As a note, if I need to replace the FPR, i'll opt for the MFI retrofit.THANKS !!!"
Here is link for you if you are going to replace the CSPI on your Silverado which should put a mile on your face if it's is a bad injector system. Good luck and keep me posted, be glad to help you keep your truck running 100%
http://www.napaechlin.com/web_app/DYK/do...
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