How come I couldnt get an arc? I could hear the wire-feed motor in the welder starting and stopping as I was welding. I had the trigger held down the whole time.

And why isnt my avatar changing?

 

There's only one reason to not strike an arc. Either the ground wasn't good, or the wire wasn't making good contact to the tank. If you used your grinder to bare a spot for the ground, and ground all the pieces to be welded, it should strike an arc every time.
One problem is possible. If you grounded the tank, but the neck wasn't well grounded, it could be a ground path issue. I sometimes use a set of battery jumper cables to ground both pieces when I can't clamp them together. I clamp one end to the ground that's on one part, then clamp the other end to the second piece. This puts both parts on the same ground, which makes for a good path.
I've got a pretty inexpensive wire feed machine, and if I prep everything correctly, it still does very nice welds. Worked great welding in the hole where my car's sunroof used to be.
I've welded a lot of exhaust systems and thin metal with it, but never anything as thin as a gas tank.

I don't know why your avatar isn't changing. Is it a Transformer?

 

Is your welder a 110 or a 220 with argon ? It looks like a weld job with out gas if you can get one that has the hook up for argon it would make a cleaner weld

 

Argon and solid core wire will definitely do better, but still need a good ground to both parts. My particular welder is flux core wire only, with no gas attachment, and 120 volt, but if everything is good it works up to 3/8" material, although over 1/4" I neeed multiple passes.

 

Its a 110V (non-gas) flux core wire-fed ($99.00 el-cheapy from Lowes) welder. I used a drill-fed wire brush to clean the area to weld (worked good) and an angle grinder to clean an area to put the ground clamp. I thought it was grounded well, but even when I had the neck and tank welded together it still spit and spudder'd. I've never had this welder do that before... it has, however, been several years since I used it.

As far as the avatar.... I changed it to my bike the same time I changed my sig to my old '80 RS Camaro. The sig changed but the avatar didnt.

 

looking at the welds i can tell u the wire speed was too fast

 

In the pic of the welder... thats the last settings I had it while welding. I did however try to adjust the wire speed while welding. It seemed that the faster speed worked better... but... nothing actually worked good. It seemed like the slower the speed, the bigger the holes but as you can see my POS welder has 2 heat settings.... "high" and "low". I'm thinking it needs a "low as hell" setting. Too much heat is my thinking as why holes were burned, but, your probably a better welder than I ever thought of being so I'm assuming (as I'm not much of a welder) that your right, and I need a new welder. lol

 

I've decided to keep the tank since its already welded (as crappy as it looks) and just J.B. Weld the holes. It will be hidden from view anyway and I just cant seem to part with the money for something I really dont need. So... now all I have to do is decided what to buy next. I figure I'd leave the drivetrain till last and just concentrate on the body.

How do I hook up a battery without an engine in it so I can check the wiring?

 

Just hook the positive to the pos of the battery, then hook the neg to battery, and get your jumper cables out and hook one end to the cable and the other to a clean spot on the frame.

 

I dont have battery cables in the car. The engine compartment is pretty much empty.