So when this occurs it cranks ok, robustly, but won’t pop, fire up, and run? hmm … well your theory about the crank position sensor makes sense, but apparently that wasn’t it. On what basis, what test , do you say that you don’t have spark? The reason I ask is b/c for this problem the cause is usually either no spark or no fuel, and solving it is much easier if you know for certain which one of those two items is the cause.
If you are certain there is no spark, given what you’ve already done, the next suspect would be the ignition module. If I had that problem I’d use my o’scope to verify the ignition module was getting its trigger signal, but if you can’t do that test, probably makes sense to just assume that the computer is telling the ignition module to fire, and for some reason it isn’t. Heat related symptoms with ignition modules are a common post here. We had one yesterday in fact, about a Ford Ranger as I recall. fyi, a cam position sensor fault wouldn’t usually cause this problem.