My kid has a 1987 nissan se pickup ,everything worked on it until he hooked the battery up backwards, now all that works is it'll crank over ,no lights etc. ,won't run ,Help where do I even start ,T

Also check the fusible links, especially as he saw smoke.

I really don't know exactly where to start with fusible links,all I've had time to do is sheik all the fuses below and to the left on drivers side,and they are all good

You have fuses under the hood too I'm sure, and fusible links would connect to starter or starter relay, they are wires designed to melt to prevent excessive current from burning up the wire harness. When you hook up a battery backwards you don't really blow accessory fuses as those only receive current when the device they power is on. It will blow a fusible link to the starter/relay, and that will kill all power to the car, just like a main fuse would, and as you lost all power (from your description) it's one of those two items. Keep in mind we can only make generalized suggestions here, not being able to see any symptoms ourselves.

You guys are awesome! ! It was a fusible link so now he has all power back but no fuel ,we think fuel pump, Thanks alot

This nissan was my dad's he parked it in1996 he thought the fuel pump was out of it,well my kid just turned 12 and grandpa gave it to him,so my kid found a battery it started up so he drove it home to our place,I bought a clutch mastercylinder and slave cylinder and my kid put those on by himself ,I helped him bleed them ,then he was putting a new battery in that's when he hooked up backwards, now with you guys's help we got that fixed and now no fuel is squirting out, that's why I believe that ok maybe the fuel pump isbad

I have an 86 2WD D21 and I had no lights, horn, beep sound when key was in, but truck ran fine. From this site I had learned to check fusible links. Mine were all fine, However my link that comes off positive terminal after unwrapping 1K feet of tape and tracing wires for a short found out that the F/link that is tucked behind battery was corroded so bad (not blown) after cleaning and hours of work. Fixed the issue.