Chevrolet Repair: van with wierd problem, vendura, tank unit

Question
hi .   i bought a 1988 3500  vendura van ( box truck) and  as  soon as i  turn it  on it  fires  but if  i  turn   the  head lights or a horn on it  will shot off and  the  engene  will not  fire  for a good  2 days .  it  will  fire  if i  put  gas on  the  thoutle body   but not   stay
it  has  a  throutle body  injection. so  u  have any idea   what  could be .  i  tested the  alternator and it is  fine

Answer
Hi Marcos,
Sounds like a loose ground.
Go back near the gas tank, and find the wire harness. There is a black wire in the harness that goes to the gas tank unit, that bolts to the frame.
Make sure it is connected to a clean spot on the frame, and is tight.
Also, make sure there is a good ground wire to the firewall, probably from the engine block.

Van