turn on my headlight and the truck dies!! WTF

[7tcutty]

87 fuel injected half ton chevy no power anything not ever air conditioning.

this is the first time ive had a chance to look at this truck

when it starts it runs pretty good needs tuneup bad! but
if you turn the light on the truck cuts out and will not start.

the truck will turn over but there is no power to the fuel pump to start the truck. if you wait (unknown amount of time) it seems to fix itself and the truck will start and run..

i did notice even if the truck is turned off if you turn on the lights you get nothing! also the dimmer switch in the column does not work..

has anyone had this prob before? and where should i start looking fr my fix?

thanks allot
karl w