I have a 2002 Z71 Tahoe that I have owned for approx. 6years. In that time it the trouble has come and gone. It will crank and run fine for days even months at a time, then it wont crank. In the past if I let it sit for 15-30 minutes it would crank. The engine will turn over but will not crank. I drive a company vehicle during the week, only drive the Tahoe on the weekends. Iv read several posts on this and havent found a definitive answer. This past weekend it did the same and have not been able to get it cranked since. btw it is a 5.3L 4x4. Crankshaft position sensor? Neutral safety? fuel pump/pressure? Any help is greatly appreciated, thanks in advance!

 

Welcome to the forum...
Those are all good places to start looking, see if you are getting good fuel pressure with ignition on no cranking.... needs to be in around 60psi
Check for spark, might want to also check compression...
Verify all of your ignition fuses (all fuses for that matter)

 

Check voltage before and after NSS.

 

All fuses are good. How do I check fuel pressure? And what is the NSS? It fired up and ran well for a couple days, now its doing it again!!

 

I believe the poster was abbreviating neutral safety switch, you will need to get a fuel pressure tester...from auto parts store or Harbor Freight... they are not too expensive ~$20

 

it wont turn over unless in neutral or park. not sure where the nss is located...have not checked the fuel pressure but on the fuel rail there is a Shrader valve that when pushed in I get what seems to be plenty of fuel while turning the engine over...tells me the fuel pump is working. not sure what to do now?????

 

If it only turns over in Park or Neutral, then the NSS is functioning.

Just because you are getting some fuel when depressing the Schrader valve doesn't necessarily mean the fuel pump is putting out the proper 50-60 psi.

 

"The engine will turn over but will not crank" I misread your statement, thought you meant no power to starter so disregard NSS as a problem.