Light problem

I have a '92 chevy S-10 all the lights worked great until yesterday when the fuel pump went out I removed the bed and installed a pump when returning the bed I noticed the rear lights dont work I went thru all the wiring and fuses could this be a flasher problem? I have front turn signals but both rear flash, then with the lights out I have tail lights and with them on I have nothing. The hazard flasher works fine but it makes the plate lights flash please any advice would be helpful I have chamged all bulbs and went thru wiring from front to back. I have juice back there and I even changed harness but no luck I need help ? Thanks