Thanks for the feedback. I believe I found the problem. I am able to get the engine to run by removing the harness from the fuel pump and straight wiring 12 VDC to the pump.
There is +12v on the harness but the ECU won't ground the other side. I was trying to wire in a test light and haven't been able to make it work properly. If I connect the light to the red/black in the test port and the blue/white test connection, the light will burn about three seconds at key-on and then go out. It will briefly come on during starting. It will not flash the "heartbeat" or trouble codes (if any).
While troubleshooting, I found that if I push in on the center of the ECU, the fuel pump will ground and come on. I was able to repeat this several times and even made a device that would keep pressure on the ECU long enough to run the engine.
After reading numerous posts, I began taking temperature on the ISC. It's hard to be sure if I'm gettting a temp from the same spot every time but it appears that the ISC is approching 190-200 degrees F.
Rodbolt17 stated in several posts that this could be due to the ISC sticking and would lead to damage to the ECU.
I ordered and received a new ISC and ECU. I tried to test the old ISC but was unable to verify any movement. Before removal, I could hear it clicking on key-off, but not everytime.
After installation of the new ISC and ECU, I want to make sure that I don't toast either one again... I started the engine and was taking temps on the ISC and when it got around 160 I shut the motor down. I don't know if 160 is normal but I'm a little gun shy at this point.
Also, before removing the old ECU I tried to verify voltages, particularly the 5 volt reference. The only place I can find it is in the test port. I may have to order the test harness' to test the other sensors. Anyway, I can only get 4.32 volts on the white/black wire at the test port. I get 12.6 to 13.5 on the red/black at the test port.
I get the same reading after installing the new ECU.
Prior to this issue, I replace all four fuel injectors and did the service on the VST, cleaned the HP fuel pump screen/filter, replaced the idle speed control filter, LP fuel filter, ignition coils and plugs.
Any guidance would be much appreciated.