Sometimes Crank /No Start KA24DE

[Looneybry]

I have a 96 240sx with a KA24DE got in a front end accident a while ago , i replaced everything in the front end (rad support , rad , ac components headlights , hood , fenders , bumper ). Now that everything is hooked up it wont start up. I bought a new battery, pulled out starter tested it came out fine, replaced fuel pump fuse. Sometimes it will crank but not start and sometimes it wont even crank. everything else like lighting, alarm, and radio work. I had a mechanic(not that experienced i could tell) come by and he seemed to think it was the security system with a kill switch. he also said the distributor wasn't giving power to spark plugs (working on getting a new one) but he thinks its the kill switch preventing the distributor. so i took out the alarm system and still nothing. i recently found something odd, whenever i moved the engine bay fuse box to the left the engine would crank but still not start? with no one in the car or pressing the clutch or turning the key?? so please help i spent countless hours and money on this confusion! feel free to text (562)4seven7-19six9
located in long beach if you can or want to help or take a look

[Looneybry]

i also have videos of the cranking on my phone i can send you.

[Looneybry]

Bump bump bump

[Looneybry]

Bump bump bump

[dbeiler]

If your car is cranking without anyone touching the key, you need to inspect your starter signal wire. If it were properly insulated, it wouldn't be able to pick up stray voltage. If the rest of the wiring in that vicinity were properly insulated, they wouldn't be emitting stray voltage. You need to take a good hard look at your engine bay wiring, starting in the fusebox since that seems to be your problem area. Somewhere you'll find some wiring with the insulation rubbed off or worn through.