1987 starting issue
 

So I bought a 300zx from my boss.

Wouldn't start, I pulled the "anti-theft starter" relay from the under hood relay box and with the key turned it and a jumper wire it cranks and starts perfectly.

Then I pulled the cover off the box by the battery and noticed one wire had been cut so I repaired this, fixing the flashing security light and no time issue.

Then the Car sat for 3 months and now I'm having the same issue. Turn the key and nothing just flashing anti theft.

Pulled relay under hood and jumped it again and it fires right up.

But wont fire up by just turning the key.

What could cause the security light to flash?

Any common problems?

trouble shoot time fun ,fun
check the door cly magnet switches , usually the alarm unlock/ release for it is in the door lock actuator
check to see no one has been slim jimming the linkage
how do we know your not a thief ? tryen to steal it

Well if I wanted to open it and steal it I wouldn't use a slim Jim since I run a tow truck and have the proper lockout tools.

I tried the whole unlock the door with the key and it didn't solve anything. So what is the proper chain of trouble shooting