I have a 2005 Sport Trac Adrenaline with a NO Crank issue. It cranked 2 days ago but today doesn't. I didn't touch anything. Just installed a fuel rail sensor and now won't crank. Also won't start when it did crank. The Fuse box doesn't look like any other I've been able to find.

I've checked All fuses & Relays and battery is new and charged

Starter is new and getting power when switched on.

 

Don't forget if we get a normal power reading from the positive side of the system when we check it, the other half of the electrical system is the ground side.
There, as you know, you have 2 choices to check . One is to remove clean and reinstall all connections coming from the negative battery post to wherever they connect top the vehicle. The other is to do voltage drop tests to verify the connections are not offering resistance that prevents full electrical flow.

I have seen many times where the cable connection to the battery post looks fine, but if there is oxidation at the lead post OR cable end, which by the way looks just fine, but IS NOT !
A simple step that can make the difference, just clean them with a wire brush, sandpaper or battery terminal cleaning tool. (Always a good investment)
These are some of the simple , but important things to remember.

 

You can bench test your starter motor and its solenoid without removing the starter itself.
1) Remove the connector that's connected to the S terminal (must remove this or you'll get cross circuit and blow a fuse instantly or damage your range sensor)
2) You don't need to use a bullet male connector and insert into that female connector, you see where that wire the other end goes where the silver nut is, you can use a battery jumper cable (red only) and clamp the alligator to that silver nut is.
It's danger to work under the car so the other end of the red alligator you don't clamp, just touch and tap to the battery positive post for 1 or 2 second (don't attempt to start the engine), does it crank now? Your goal is to test and see if it cranks for 1 or 2 second.

This test is to bypass just your ignition switch and range sensor and starter relay at the fuse box. If it cranks that way then there is an issue between the S terminal to your ignition switch, could be range senor or ignition switch or fuse or starter relay.

 

Found the problem. Grounding strap on post "m" was broken. thanks

 

You got the right part just the wrong description That strip brings power from the solenoid to the starter motor. They do give out when starter motor is drawing excessive current for an extended period of time. Could be internal or,,,,,,,,,,were there long cranking episodes before this happened ?