I have a 1999 Chevrolet S10 4.3L with possible ground issue? I have no headlights/tail lights, dom lights, dash lights, and no power to the fuel pump. I do still have parking lights, and I have checked all of the fuses and relays none are bad. could this be due to a bad ground and if so where should I start to look?

Tail light bulbs can blow fuses when they fail. Remove the bulbs and test them with a meter, or with a piece of wire to the battery terminals.

Check the grounds and connectors that are near the rear lights. Check underneath for cut or broken wires.

The dash lights are more of a puzzle. A corroded or loose connector is the most likely. Older vehicles do have small capless bulbs in the dash.

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Sounds like you have a electrical short in the brake light switch. Finding electrical issues can be a bit tricky but I would start with the under dash relay you hear clicking when you depress the brake pedal.

current for tail lights and dash lights is coming from headlight switch Brown wire.
Don't forget the ground. or common ground
hope it helps

if the cables were put on wrong yes..since it sounds like you are not mechanically proficient, go to a shop that specializes in auto electrical..they should be able to fix fairly inexpensively(cheaper than the dealer)..

main power issues .. check battery connections.. check fuseable link wires under hood,..check fuses in fusebox for blown fuses and check wiring harnes ground connections especially by the headlights..

There should be a fuse for the dash lights and one for the tail lights.
A mechanic would check for voltage for each circuit at the headlight switch and go from there.

it could be the dash board light switch is bad.
may be fuse.
check for power at the tail lights with test light or meter.
may be a fault ground ( not likely) or a bad taillight wire.
did you check the bulbs they have more then one filament in them.

Does it do it if you just turn the parking lights on? I would suspect this is a bad ground causing the head or tail lamps to pull through the turn circuit. I came across this years ago in an 85 cutlass. the ground for the tail lights was very rusty. Cleaning and regrounding solved the issue.

you might have an open ground wire on your brake/tail lights .. when you apply the brakes then power would flow thru the brake light (not see ground) so would then provide power backwards thru the parking light (common ground open) to all the other things connected to the parking lights .. like the other parking lights and dash ... when you turn power on to those things (headlights on) then there is 12 volts on both sides of the light .. thats why the lights quit working ... if the missing ground is the problem then most of the lights that are improperly turning on should be at a lowered brightness level.. interesting problem .. its also possible to have a brake light bulb that has the common ground open inside or not making connection with its socket .. i would start by removing the brake lamps and see if the problem goes away .. if it does look for a broken ground or damaged lamp ..

Head light Switch Most likley