Wet distributors are very, very common on these. I see a rash of them every time it rains.

Pull the doghouse ( <img src="/forums/images/graemlins/frown.gif" alt="" />sorry) and use a #20 torx to remove the distributor screws. I usually unplug the 3 plug wires on the driver's side too. Just make sure you mark them. The cap has cylinder numbers on it to make it easy.

If there is any sign of green or white powder, replace the cap and rotor. I cannot stress enough the importance of using AC Delco parts. I've never seen an aftermarket cap and rotor that worked for very long in this application.

Make sure you dry the inside of the distributor very well prior to re-assembly. I use brake cleaner to remove any moisture. Just be sure to give it enough time to evaporate before you put the cap/rotor back on. It could be exciting if you don't.

The rotor screws are #15 torx.

BTW, you may find that the inside of the cap is still wet when you get in there. That's not uncommon with this situation.

Distributor caps can fail internally too. If you don't find signs of moisture, pull the coil wire from the cap and check for spark. If it lights up real well then plug it back in and pull a plug wire at a plug. Probably #5 is the only one you can reach easily (driver's side, rear of engine). If no spark there, then the cap/rotor is still bad.

I forgot to tell you, it is customary to unplug the electrical connections to the coil or to the ignition module and crank the starter to make sure the rotor turns whenever you have the cap off for a no-start. Just be sure to plug everything back in.

If you have a fuel pressure gauge it wouldn't be a bad idea to check your fuel pressure when you have the doghouse off. It should be ~50-55 PSI when keyed on. The pump runs for 2 seconds at key on. Watch the guage for a couple minutes. It should hold a steady pressure even with the pump not running. If the pressure drop, let me know. There will be more to do there.

One more thing, don't think that you're immune to distributor moisture issues just because the cap/rotor are new (if they are). I've seen vans like yours come back on a hook the very next day with the same problem in spite of a brand new cap/rotor. Usually happens when aftermarket parts are used.

Let me know if you need any more help. I work at a GM shop as a drivability tech, so this is something I've encountered a number of times. I'd be glad to help.