Check the ground clamp for correct assembly; be sure that the ground cable has enough insulation removed and copper wire exposed to provide a good connection to the ground clamp. Check to see if your ground clamp is attached to the actual surface metal, which should be free of paint and rust. You should position this clamp as close to the area that you are going to weld as possible.
Check your electric source. It is better not to use an extension cord. However, if you must use an extension cord, use a good 10-gauge cord that is not more than 20 feet long. Make sure you are using a 20-amp dedicated circuit.
Make sure that the wire feed speed is set correctly. Adjust the speed in small increments until wire does not stick to the surface, and before it pops back toward you.
Make sure that the surface being welded is clean and free of grease, rust and paint.
Make sure that the polarity is correct for the wire that you are using.
If using gas, the torch must be positive and the ground must be negative. If not using gas, torch must be negative and ground must be positive.
Check to make sure the wire is not damp, rusty, or oxidized. Make sure that you are using the appropriate wire: Flux E71T-GS or E71T-11Mig ER70S6.