Soldering instead of crimping

I soldered some wires in my Toyota MH engine compartment. One joint had six wires 14 or 16 gauge. My 40 watt iron wasn't working so I used my 260/200 watt gun. I still could not get the wires tinned completely it seemed. I tin them then solder two at a time then heat and stick the pairs together. Can someone tell me if I need a higher wattage iron or another solution to solder wires that have old maybe weathered ends. On fresh copper wires the heat flows great. Is there a technique to get old copper wire to tin properly or is this the best I can do? Thanks