Chevrolet Repair: Impala question, 3800 engine, electrical level

Question
I have a 2000 Impala LS with V6 3800 engine.  About two years ago, every month or so, if I drive more than 40 minutes, and shut the car off, it may not start up again.  It eventually starts again if it sits for at least 15 minutes so it's never caused a major problem.  It's obviously sporadic-I've gone 4-5 months recently without it happening.  It's always worse in the summer-definitely seems heat related.  It has never happened during my usual weekday usage as I only drive 25 minutes to work and that's too short.  It has never happened from rest (like in the a.m.)-only after driving for a longer period of time.  I've taken to a few places and because it's running and everything checks out, there's nothing they can do. They tell me to bring it there when it doesn't start but its a Catch -22: by the time it's brought somewhere (once towed), it starts up just fine.  It's been very frustrating and I would appreciate any insight. Thanks

Answer
Hey,

  Two things you want to do:

A: Have someone scan it for trouble codes in the PCM and BCM to see if there is any security codes like an invalid key code.  The ignition cylinder contains a security device that goes defective all the time.

B: Have a shop test the fuel pump waveform with an occilliscope and a low amp probe.  This test will show the state of health of the pump on an electrical level not a mechanical level.  Even though a fuel pump has good pressure and volume it still may have a defective winding or brush that will show up on this test.  If you call a shop, talk to a technician and just ask to have a fuel pump waveform analysis.  If they say "HUh?" or "errrr I don't understand what you mean." Call another shop until you do.  This test is definitive and will show intermittent anomalies with the pump.  A knowledgeable technician can tell you pump condition, rpm and current flow at the fuse believe it or not.

WAyne