99lt- 4wd -4.3 -auto 120,000. Bare with me fellows.. I love this old truck, but now beginning not to trust it..Got in it yesterday morning and it wouldn't start. Noticed that I didn't hear normal fuel pump noise, but didn't worry. SOB wouldn't start. Several 5 to 10 second starter bursts; with no response. Not one hit,, as if NO fire to the cylinders.. Waited & wondered 5 mins; then several more attempts; with zero response from anything/anywhere.
Battery/starter strong, no sound from fuel pump; gotta be a bad pump??
Running late, can't worry about it now, use wife's car and worry about this sob tomorrow.

Next day (today) got in it and turned on ignition, still no pump sound... Suspicion confirmed, bad pump..... Tried it anyway, and friggin thing started like new; I mean it started on first 2 or 3 rpm... Repeated starting several times; each time PERFECT. Still no pump sound.

What the hell is going on??? Yesterday couldn't beg/borrow/steal a start...
Did nothing to it; today it starts & runs perfectly.

I've searched & read over 30 pages of starting problems; and still at a loss for answer.

Any help greatly appreciated.

 

Three things that are super high failure that often cause what you are experiencing:

Fuel pump
Ignition switch
Crankshaft position sensor

All three not only cause the problem you describes, but all three are well known to fail prematurely. Of the above parts, it is not if but when the fail and leave you stranded, and note they typically fail intermittently, making trouble shooting hard.

The CSP is very easy to replace(FSM states a tech II scan after replacement for learning- but many don't do that step)

Ignition switch moderately easy to replace

Fuel pump often an all day job to replace,

Make sure you but DELPHI or AC/DELCO only for the above three parts if you select to replace them.