WONT START- Placing bomb in van now! Shhh..

HELP! I am about to blow this van up!
This freakin' van is making me very mad.

Background: 87 Safari, 4.3 V6, Auto, 2wd, 165k mi.

I have replaced nearly everything under the sun..
Here's list of new items right off the top of my head:

Fuel pump, relay, fuel filter, injectors, regulator..
Dist. cap, rotor, plugs, wires, coil, ign. pickup, finally the distributor.

PCM, TPS, EGR, IAC, O2, EGR sel., All vaccum lines, PCV, Air filter, cleaned the TBI body...

I am looking into a bad engine ground, possible bad PROM and CALPAK now, but I am grasping for straws...

Here's an exaple of what it does...
Short trips with long (couple hours) lay overs.. Van is fine.
Long trips with short lay overs... your stuck.

Just a while ago...
I went out, cranked the van first try, drove it around the block several times while cold. Came back, parked it in the drive and let idle for about 30 min., when I came out to check it, it was not running and would no longer start..

When this problem is present... the injectors are not spraying fuel.

I am tired of chasing this problem and being towed home..
If anyone has some insight... please help.

Just a thought. I understand that, if oil pressure is too low, the oil pressure switch shuts off the fuel pump relay and stops the van to protect the engine. A bad sensor can also keep it from starting. If you oil pressure is low (long trips and hot oil = lower pressure) the sensor may cut the fuel relay out until the oil cools and pressure comes back up. Is your oil pressure ever low?

Is your oil pressure ever low?

I've been thinking about that myself, which is why I orderd a Oil Pressure Sensor today..
But.. I am not aware of the oil level ever being low. The engine uses very little oil, and it does not leak. Everytime I have checked, it has always been in the acceptable range. Looks like we have having the same thought process on this. :)

This sensor measures oil pressure, not oil level. So, you could have full oil in the sump and no leaks, but if the pump is not putting out enough oil pressure, or the sensor is bad, the computer would think there is not enough oil pressure and you would have the problems you report. Let us know how this works out for you.