How to find weapon parts during a Scavenger Hunt

Best bet is to check the borderlands wiki, those scavenger parts are always in the same location, and the green quest marker only leads you to the general area, not the exact parts.

What I have always done (playing the PC version) is to select that quest in my quest log. Follow the waypoint. When you get to the location the waypoint indicates, stop and look around. Usually the piece is pretty easy to find. But there are a few times it will be in some difficult location. Usually up high and on a ledge you have to jump too.

Remember that the waypoint is not exact. If you get to the waypoint and you just can't find the piece look around. I've seen it be as far as about 100 feet (pretty subjective in-game I know).

Don't forget to check inside containers, behind buildings or even inside vehicles (there's one piece I remember I had to jump up on top of a wrecked vehicle and the look carefully inside the cockpit. It is hidden beneath some junk in there and seeing the "glowing green" isn't obvious. Once you see it though it's easy to pick up.

HTH.

After your arrival on Pandora, you should have had your personal ECHO Communication Device and Heads Up Display (provided to you for free by the Dahl Corporation) from a CL4P-TP General Purpose Robot (more commonly known as Claptraps). One of the features included is a Digital Bearing Module (more commonly known as a compass) which, in addition to other functions, allows you to locate objects of interest in your near vicinity.

The easiest way to find those weapon parts is to look for the loot icon on your compass when you are standing on the spot indicated on your map. they may point towards ammo or other items, but when those are picked up, the only thing remaining are the weapon parts.

Do note that your compass does not indicate a height indicator for the location of an item, so be sure to look up and down for ledges and other type of height differences.