Have you tried PreHeating the work to 300 t0 400 F?

What size electrodes are you using? what size and shape of aluminum? If you are using 4043 i think you are best suited for DC+.

What process do you use with the Inweld A3 electrodes? If they are GTAW (TIG), then I have no experience with that. If you are dealing with GMAW (MIG) then I would say you need some way to control your voltage in order to balance it with your amperage.
CHG

You will find that aluminum is the beast of the industry, there are many types and variables involved. Without knowing more I'd make the following suggestions;
1- call your welding rep and ask for parameters, they should be able to help
2- call inweld tech support and tell them your troubles
3- if your aluminum has any depth you will need to preheat, CLEAN, weld, post heat.
Aluminum dissipates heat rapidly and is VERY tough to get a weld started on.
If not clean you are defeated before you start.
Its a pretty expensive rod to waste trying to find suggested settings, let the company tell you.

Stick welding aluminum can be a challenge for even experienced welders, but here are some tips. First and foremost is the correct current, and that is D/C reverse polarity.Secondly, remove as much oxidation as possible, (try a S.S. wire wheel). Third keep electrode @90 degrees from work piece,after initial arc if electrode does not start, the flux coating will melt around the tip of the electrode and it will be nessecsary to remove molten flux from tip before restriking. For .125 dia. electrodes try amperage range 110-150. Good Luck

Cleaning is most important. If this is stick, try striking initial arc on piece of carbon steel placed near the joint. After arc is started, then drop off into your joint.