got a 1999 chevy silveraldo with old style throttle body,wont start when it sits more than 6 hours once it starts runs fine.wondering if there is a sensor that injects shot of gas when starting thanks

sounds like the fuel pump... try turning the key "ON," but not starting it for about 10 seconds. Then turn it over and see if it doesn't start right up.

Could be a clogged fuel filter not letting the fuel through fast enogh on startup after the fuel pressure has drained off.

Could be a clogged fuel filter not letting the fuel through fast enogh on startup after the fuel pressure has drained off.

Yeah, and for the $6 for a new fuel filter, I'd go ahead and change it

Yeah, and for the $6 for a new fuel filter, I'd go ahead and change it
Had the same problem try to change the fuel filter frist. If that does not work then check to see if you have a check motor light on, if so it is the mass air flow sencer. But if not when you start up your truck and if it makes a loude ring or busing sound all the time it is the fuel pump. If not that it will probly be the fuel presure regulator. I have the same year truck and i hear this problem alot. Mine was a combonation of the fuel pump and the mass air flow sencer.

I had the same problem with my 2001 5.3. Changed the fuel pump and now its good to go. OEM fuel pump from ebay $135.