Okay, this is more or less what you want to build:
Listed here are the parts and tools you need build it as well as where to scavenge them from:
-1 hacksaw, for hacking off necesary parts from other vehicles. The best way of finding it is by killing lots of regular zombies until it drops, so keep your watch for them next time you enter a city. Can also be found in garages (safer place to loot), hardware stores (depending in the situation, it could be pretty easy or a complete pain in the ass) and Public Works (somewhat hard loot due to the big numbers of shocker zombies inside)
Tools:
-1 Wrench, for wrenching wrenchable things (for constructing and removing parts). Found in the same places as a hacksaw, zombies drop it even more often.
-1100 units of Duct tape, for installing parts. Found in rolls of 200 inside house wardrobes, Apartment buildings often have at least 600 units of duct tape inside them, so search in those, if you cant find those, just loot houses until you find them.
-A Welder is a possible alternative to the ductape, but those only spawn in Garages hardware stores and public works and are much harder to find, so I’d concentrate on finding duct tape instead.
Parts that youll need to remove from other vehicles:
-2 frames found literally everywhere, just remove them from the first vehicle you find.
-A motorcycle engine, found on motorcycles, in this special case the smaller the liter capacity, the better.
-An alternator of every type (car, truck, motorcycle) found on cars trucks and motorcycles respectively.
-A storage battery. Found on electric cars (those cars with yellow(#s) on them), you can replace this part with a truck battery but ill try to find the storage battery.
-Controls, intact ones are found on most cars/trucks/motorcycles, just remove those and call it a day.
-A red emergency light and a blue emergency light, yes, you need one of each type to generate continuous light. Most emergency vehicles haveworking ones, they shouldnt prove to hard to find.(If you manage to find a floodlight (found in the Luxury RVs, replace the emergency lights with them.
-A small metal tank, from motorcycles
Building it:
You ll need 3 in mechanics, all the above mentined parts and tools. Once you have those building the generator is pretty straight forward, while in the basement press * to bring up the build menu and select vehicle construction. Then instal the parts in the same order as pictured above( note: if you looted the three types of alternator, just keep adding them after you add the last one) once you finish installing pieces in the first square, move up add a frame the remaining light, and fuel tank. And you generator is done load the fuel and some batteries and you can start using it right away.
If you installed the three alternators, model produces aproximately 4 units of charge per 1 unit of fuel, for every 45 min it runs. (you dont have to wait for the battery to be completely full before turning on the lights, you may turn on the lights at whatever moment you please)