Buick died in Garage - please help

Hi all, I need some help PLEASE. buick lesabre 2000, 98k on it.
Here is what I did, and what happened.(please excuse the length, but rather I tell it all)
Did a general service of Oil change & airfilter change. Replaced plug leads & plugs(Bosch platinum).Drove to the gas station filled it up & added Injector cleaner into the tank (Techron) and went for a drive. Made 6 stops and drove a total of 76Miles, parked in the garage and changed the rotors and pads. Came to re-start it. It fired & ran for 2 seconds then nothing, this is how it repeatedly has behaved.If I crank it straight afterwwards nothing. It just cranks over whether my foot is flat on the gas or off the gas. If I wait
5 minutes and crank it , it will start for 2 seconds again and repeat as above.

Here is what I have tested and replaced:- Replaced ignition coils and module, (called a car specialist who has a call in program on the local radio station and he told me to do that.) Replaced fuel filter,tested fuel pressure with the following readings:- pump primed it reads 47, when I start and it runs for those 2 secs it goes down to 40, then when I crank it and it wont start it goes up to 50.
The injectors, I tested voltage with the ignition on it read 5.25volts, when cranking it read 3.8 - 4.2volts.?? Pulled the plugs out and there is fuel on the plugs. Tested the plugs, and there is a good spark. I diconnected the positive on the battery and left it off for 5 minutes and tried it again but no change? Can anyone assist, who has experienced this or who has a good idesa of what it could be? I discounted fuel pump, as it seems in range? The strangeness for me is that I drove it into the garage and it just wont re- start??:screwy:

You said you have spark, was this checked after the 2 sec run and then no start cycle?

You said you have spark, was this checked after the 2 sec run and then no start cycle? Not immediately after, but a while inbetween I pulled the plug and tested it.I'll test it with one plug out and see

The best way to test spark is to use a plug gapped at 100 thousandths, hooked up to the ignition wire and use a ground wire to the plug body (metal part) to engine ground. (Jumper cables work fine). Then, turn the engine over, to see if you have a "hot blue flame" across the gap.

apologies for the long delay in replying, I did as you sugested and it sure gives a nice bright spark.

Spray carb cleaner or starting fluid into the intake see if it kicks over. Any aftermarket anti theft device or alarm on the car? Also may have to get a noid lite and see if you have injector pulse.