I have a 91 L98 (63000 miles) everything original except has after market radio. It runs and drives almost like new. Here is the problem from time to time after driving it will not start. Turn key absolutly nothing from engine. Let sit for 30-40 minutes fires right up and runs like a charm. I have been told everything from security system, chip in key, starter, battery ect. Does not happen everytime I drive, seems to be on the longer runs that it happens. Everything works when it will not start, so I eliminated the cause being the battery. Any thoughts this problem? Thanks in advance!!

Is the whole car dead when this happens? If so, then you most likely have a bad connection at the battery, or on the starter. If everything else works, but only the starter will not turn, it is most likely the starter solenoid. Heat can make it do weird stuff like that.

l98's are notorious for hard or sometimes not starting if solonoid is hot....does this seem to happen after u've driven the car up to full operating temps, then shut it off only for short time then try to re-start?If this is the case heat is your culprit....

Thanks everyone. Will do the VATS bypass first. Saw one on Mid America that has 3 positions so that VATS can be switched on when needed for security. Got my key code today from dealer. If this does not work then will try heat shield on starter. Thanks again to everyone for imput.