'97 Explorer Strange Starting Problem

I'm having a problem with my '97 (4.0 OHV). It seemed like the longer it sat
the longer it was taking to start when cranking the engine. I thought it was
a fuel problem but a few days ago it wouldn't start at all. I checked for
spark with a timing light and NO SPARK. I can hear the fuel pump pressuring
up when I turn on the key. Here's what I checked so far:

Black wire going to some unknown (I couldn't find it in the Hayne's manual)
small black device bolted onto the coil pack was partially eaten through by
mice. Checked for continuity and it checked OK. Cut out the bad part and
soldered it anyway. No start.

Battery: all cells test very good with a hydrometer and it charges back up
(after trying to start the engine) quickly with a battery charger. Voltage
is OK.

Pulled the fuses for the ignition and put them back: all OK. No start.

Tried to start with fully charged battery and charger connected: no start.

Voltage to coil with switch on: OK

No start.

Coil resistance: OK

No start.

Checked voltage to crankcase position sensor with switch on: OK. The funny
thing is when I connected the voltmeter to the CPS connector I could hear
the fuel pump pressuring up.

Started right up!!!

Could a small amount of corrosion on the CPS connector cause the voltage to
be too low while trying to start it and then after it starts it just doesn't
care any more? It runs fine once it starts. I have started it several
times, several hours apart since the CPS incident and it has always started
quickly and strongly. I sprayed a little WD-40 on the connectors to help
clean them and prevent corrosion. I tried starting it with the CPS
disconnected and it cranked but would not start. When I reconnected it it
started right up.

Or is it possible that a bad ignition switch could allow it to crank but not
start? Or what about an alarm system? There was one on this Explorer that I
had removed when I bought it used from a dealer. There is still a red LED
installed in the dash. Are there alarm systems that will allow it to crank
but not start? The ignition key does not have any microchips in it (from
what I was told by the Ford Parts Dept) and hardware store duplicate keys
were working fine. The original key has the same problem.

Any other ideas? I did a google and could not find any other Explorers with
this particular problem (or at least none where the solution was posted).

I intend to check the fuel pressure if I can ever find a local auto parts
store that has the correct gauge. I also plan to get an inline spark tester
if I can find one locally. I really don't want to pay $6 shipping for a $4
spark tester. Is there any reason not to use a timing light to check the
spark? It's a basic, cheap inline light, not an inductive type.