Does my Ford E-150 van need to be running when doing a diagnostic OBD II scan tool?

My van started giving me trouble a month ago but only when it was wet outside. It would sputter here and there but nothing major. I assumed it just needed a good tune up since I just bought this van in January and I'm sure the prior owners didn't care to spend more money on a car they were selling. So it finally it died on me while I was driving, sputtering out. It will crank but won't kick in. So I did the tune up- changed the fuel filter, spark plugs and wires. ( No distributor cap on my model) It started and ran for a minute then died and now I'm back to square one. My check engine light is NOT on and the fuse for the dash is fine. (but my cigarette lighter fuse isn't working) Anyways, I got an OBD II/ EOBD scan tool to run a diagnostic anyway since I figured it wouldn't hurt and I'm trying to eliminate everything I can so I can close in on the specific problem. The scanner said " NO CODES FOUND" but, as I said earlier, the van isn't running. Will the fact that the van isn't running cause this reading? Do I need to get it running to get an accurate read from the scanner? Do you have any idea about what might be wrong? I checked the fuel pump, and the air filter, and they're both good.

Unfortunately for me, it's been raining since I broke down 2 days ago and still is! So I can't be sure if the moisture is really causing all this. My auto info is below. Any help would be greatly appreciated! Thank you!

2000 Ford E150 1/2 ton Van 8 Cylinders L 5.4L EFI
120,000mi.

Added (1). Yes, the vehicle has to be on. The issue was my fuel pump. I checked the fuel line- no fuel coming out. Tested the volts going to fuel pump, that checked out fine. I went to used parts store, bought a used fuel pump for $75, and replaced it myself. I actually cut out a square above the fuel tank w/ a saw to gain easy access to the pump. This saved me 4 hours since I didn't have to drop the entire tank! (you can see it on youtube - "replacing fuel pump without dropping tank! E-150") Thanks everyone!

Key on wil have scan tool read. Ignition on position. On e codes checked we can run engine and check other readings.
Symptoms described would point to moisture shorting ignition. Check crank sensor and cam sensor connections.
We also describe an engine having no fuel pressure… Start run one minute cut out and non restart are typical no fuel pressure issues. Recheck pump runs. Check fuel line.is pump running but no pressure? If so check fuel filter.
Some codes won't show on some scanners. Here main dealer WILL be able to read all codes etc both non and in running condition.
Main dealer ought to be able to pinpoint fairly easily the fault.
Balance cost versus no use of vehicle…

Key on engine off to read codes… You have none… Right?
what was the fuel pump pressure… And how many pounds did it drop with key off?
What's air temp when this problem occurs…
that vintage f150 used to have a pair of MEGA fuses on the firewall that could cause stalling…175Amp the fuse may look good but be cracked…

No. You just need the key on.