@xianos, like tiff said make sure the
tank is screwed down tight, if it already is take apart the switch and give it an iso bath, while your at it you can sand down the screw head flat so it makes better contact w/ the neg side of the batt,
sand the top and bottom of the spring flat and sand the surfaces where the spring sits, as well as the top of the screw post.
also while your in there, do the same thing to the spring under the atty
most issues w/ not firing are in the coil, most issues w/ intermittent firing are gonna be in the switch.