Funky Spark -> No Go
 

On a Ford E150 Econoline van, everything ran fine before a tune up.

After the tune up I could not get it to start again. Testing the center wire of the distributor cap produces a spark and starter turns engine freely, but putting the wire back into the cap, it seems like it loses all power and fails.

Putting the old distributor cap back on produces the same result. (even with a battery charger set to boost).

Battery and battery cables are brand new and both starter and alternator have been tested ok at Autozone.

I'm not sure what more to include, but any help is greatly appreciated.

Thanks!

Did you do what I think you did?
Did you replace the plug wires on the cap one at a time or did you decide to put them in the way you thought they should be?