We have a 2000 F 250 7.3, 4WD with an ignition problem. #20 fuse is blowing when engaging starter. Removed starter, tested, its good, put back on. Replaced solenoid under hood, still blows. Old solenoid back on to ensure wires were correct because of different bolt pattern.. still blows. Pulled small ignition wire on solenoid, turned key, not blowing #20 fuse. Left key on, jumped solenoid, it started not blowing fuse. Before this all started, the key was sometimes hard to pull out of ignition. If it is in ignition area, what should I check?
On neutral safety switch there is one wire of many in harness one is looped up to back of transmission housing to a 1" button , then back to neutral safety switch harness., Is this button a sensor? Could this be what is blowing the fuse? Thanks!

 

Here is one way to help isolate the location of the short circuit causing the fuse to blow when the key is turned to the start position.


If you unplug the plug on the neutral safety sw and turn the key to the start position.
If the fuse blows, the short is between the ign sw and the neutral safety sw.


If the fuse does not blow, the short is between the neutral safety sw and the starter relay.
What result did you get ?

 

Think your looking at the trans Output Shaft Speed Sensor. Its not related to the start circuit protection.

If its fuse 20 in the CJB (not the BJB) Fuse 20 protects the GEM input and the ignition/start trough clutch pedal jumper connector (auto harness are equipped) as well as the DTR (trans range sensor) and starter solenoid.
Like Hanky mentioned,, if the DTR is disconnected, and the key cycled/Start and the fuse pops,, its not the range sensor or starter solenoid related. Next, and the DTR connected, If the fuse does not pop it could possibly be the DTR (or connector issues there) or a starter solenoid etc issue.
Might try cranking the engine in Neutral to see if there's any diff,,
If the DTR is suspect, connector removed, you can jump/bridge the DB/OG and TN/RD circuits and the engine will crank bypassing switched/position control.
Caution,, it will crank in any gear position and as a 'test only'.

Removing the key,, may not be your issue, but was common for the wing area of the locks set to loss its crimp to the lock portion. Basically the wing portion would rotate slight making it difficult to insert/remove the key. Not the only reason, but something to look at..

 

When you removed small wire and fuse did not blow, did you remove it from the starter relay or the solenoid on the starter itself?