I have a 2000 ranger XLT with the 4.0 that ran fine, till 3 weeks ago it wouldn't start. I replaced the fuel pump and filter...also replaced the crankshaft poss. Sensor. Im also not getting spark...as I pulled. Plug and turned her over to see if she was sparking and she wasn't ...idk what else to check.

 

CEL(check engine light) should come on with key on, that means Computer has booted up, no CEL = no computer
CEL should go OFF when starter motor starts to turn the engine over, that means Computer is getting a good timing pulse from Crank sensor, no timing pulse CEL stays on and no spark or injectors

If CEL comes on with key on, and goes off when cranking engine over...............and no start then do 50/50test
Spray fuel into the engine manually, gasoline, quick start, carb cleaner, brake cleaner, pretty much anything the burns well, lol
Try to start
If it fires, starts and dies spark is OK issue is fuel
If it doesn't fire then no spark(or no compression), and FYI its the only way to test for spark on a Waste Spark system, which is what you have
50/50 instant results, and no guessing

Distributorless engine's spark system is not the same as the old distributor systems, so spark testers and/or using a spark plug often won't show spark at all

Test coil for 12volt key on, 4 wire connector, unplug it, red wire should have 12v
If not then check fuse 19 in Cab Fuse box, but CEL wouldn't come either if this fuse was blown

 

The cel comes on and stays on regardless because of a P420 code due to the rear o2 censor but I'm checking the coilpack now trying to see why I can't get spark.

 

I had the same issue on my 1995 4.0 OHV after changing the crank sensor. Ended up being the polarity of the wires on the crank shaft position sensor harness. Not sure how that could happen but one of the guys at the garage had seen it before. So we flipped the wires and it started right up.

might be worth taking a look.