Last week I purchased a 2002 7.3 diesel Excursion. A few days after purchasing, it wouldn't turn over. No crank, no start. I cycled through the gears and it turned on fine, so I chalked it up to anti-theft programming.
Two days later, she wouldn't start for real. Nothing helped. Troubleshooting led me to believe it was the starter, so I replaced that.

Installed the starter and she turned over fine three or four times, no problem. I thought it was fixed and then it goes again.

No crank, no start. Cycled through the gears and it turns over.

Is it the anti-theft or am I way off base here?

Checked fuses. Checked batteries. Checked the alternator. Starter is now brand new. Doesn't blow compression.
TIA for any help/insight.
Bench tested the starter after I took it out and it was bad.

 

Few things I would recommend here.
First keep the batteries fully charged while checking things out. You need to keep them at 12.6 volts when resting otherwise you may drop down to or below 10.5 volts while cranking and that will lead to a no start. You will need a real charger not a maintainer or a trickle, this can not be stressed enough.

First..Connections.
Check all connections on each end of the batteries. Physically move, wiggle, touch the cables. Any burnt, discolored, or loose wiring needs to be addressed. You have two grounds on the front of the block each from the batteries, insure they are tight and in good condition. You will also have a ground going from the block to the frame on at least one side maybe both starting at the primary block bolt. You should also have a smaller cable usually about 10 gauge from the battery to the fender on at least one side if not both. You also need to check the starter connections both trigger and main feed. If I remember correctly the 02 does not have a fender starter solenoid but if you do check that as well.

After all connections are checked measure both batteries while connected, they need to match voltage, if not you have bad cables somewhere so check again.

Second. Codes
Are you getting any codes or lights from the dash? OD light blink???
You can not rely on the auto parts store to scan and tell you what you need. The scanners they have there for use or purchase do not read our trucks properly. Get FORScan or FORScan Lite and the reader they recommend.
Check the Neutral Safety Switch on the transmission as well as all the linkage. The switch will cause a not crank condition. Try cranking in Neutral instead of Park.

Are you getting the Wait light? If not your computer will not come on line as the fuse is blown.
Also...
Keep the fuel tank above 1/4 unless you have done or have proof the shower head in the tank is new. Recommend you look into the Hutch/ Harpoon mod.
Keep the oil fresh and correct. Do not use additives in the oil the HPOP will not like it. Use proper diesel oil. I will not tell you which one but there is a Ford list so use it.

Pull the Fuse Box covers and check them out as well. (All of them)

Can not help on the PATS system but others should be along soon.

Just a few things to look at so let us know.

 

Second battery. If you got a known good battery throw that in there. You would be surprised on how much amps that engine takes to crank. So even a good testing battery for say like a little four banger could be a no crank for that monster. But this would be my first step and new will always give you a good piece of mind..


Plus a bad starter puts a lot of strain on a battery...

 

If you cycled through the gears and it worked, have you checked the shift linkage?

 

I am a second on the Neutral Safety Switch it's on the drivers side of the transmission with the shift linkage.