GMC Repair: 2002 GMC Envoy SLT, gmc dealers, gmc envoy

Question
2002 GMC Envoy SLT (6 cylinder) – starts fine when cold (for example, first thing in the morning). When making short trips, and letting the car sit for a few minutes (running errands) the car will not start. It will crank, but will not turn over. Each time, the car has been parked for approximately 5 – 30 minutes. When this happens we wait for around 5 minutes, and it often will start. If not, we wait another 5-10 minutes and it will usually start. The longest we’ve had to wait is 60 minutes. Once the car starts, it runs fine. The problem does not occur all the time. We’ve taken the car to our local mechanic who has had problems diagnosing the problem because it cannot be replicated. Today, the problem occurred twice while running errands, so we took it to the mechanic. It happened numerous times at the mechanic, but he could not determine what the cause was. His best guess is a problem with the car’s computer, because the readings he was getting on his diagnostic computer were very strange, but that is only an educated guess. He is still not sure what is causing the problem, and recommended that we take the car to the dealer. We have not had much luck with our local GMC dealers. We appreciate any suggestions you might have regarding the best way to get the problem resolved.

Answer
Hi
If this is an 02 Blazer Envoy package, with the 4.3L V-6 engine and it cranks but does not start, my best guess would be first to get a major tune , plugs, wires, Dist cap, Rotor, fuel filter, air filter, etc.. I would also have mechanic monitor the fuel pressure, 60-66PSI NO MORE NO LESS. If they have less than 60, the pressure is not great enough to spray when the poppets are energized.
If it is a 2002 Envoy, with the 4.2 inline 6 (S motor)  my personal guess would be the Ignition switch. Not the key cylinder, but the actual electrical part of the swithc, located in the steering column, under the lower Column cover. It is small, about the size of 2 boxes of matches and is shaped in a 90 gegree angle (shaped like an "L")There was issues with the switches, especially the earlier years (2002-2004up  ). It is a fairly easy repair, the switch should cost  well under $100.00, and maybe 1-2 hours labor. If ya'll decide to repalce this, just make sure it is "timed" properly(small gears), same in as the same out.
IU hope this helps
Good Luck, God Bless