You have way too many things to address here. There has obviously been hands in there modifying things that we have no way of knowing or figuring out. The engine can't run without a mass air flow sensor signal. Hooking "extra" wires to the battery invites a drain from who-knows-what. No one would just assume any leftover wires go to the battery. You've also started randomly replacing unrelated parts which adds more variables to the original problem. What is a "heat sensing unit"? Do you mean the coolant temperature sensor? There could be two of them. Intake air temperature sensor? What's an "ignition sensor"? Do you mean the crankshaft position sensor? Camshaft position sensor? Distributor pickup assembly?
Cranking for more than few seconds suggests a fuel pump of fuel supply problem. That would appear to be completely unrelated to most of the other problems.
Probably the best place to start is by finding a manufacturer's service manual, (not a Haynes or Chiltons), and using the wiring diagram to determine which wires go where. Along with melted wires, you'll have to determine what's at the other end and if applying battery voltage would have damaged anything else. When the person you bought the truck from disconnected the mass air flow sensor and left it that way, that shows they didn't know what they were doing or how to fix it properly. Some engines will run off the MAP sensor as a backup, but only Chrysler has been able to make an engine run properly without a mass air flow sensor. Even if you get the engine running, it won't run well until you correct the mass air flow wiring. Look for a service manual on eBay or at an old car show swap meet. Some vendors sell nothing but old manuals.
To add to the misery, it sounds like you have a generator / charging system problem if you need a battery charger. I can help with that diagnosis once the engine is running. All you'll need is an inexpensive digital voltmeter.
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Wednesday, December 28th, 2011 AT 10:46 PM