sounds like it is being kept from seating by interference with the head.does the tip of the glow plug stick out above the head?if so make your own connector by taking a 1/16 whell collar and soldering a flexible wire to it.secure this to the center lead of the glowplug by tightning set screw till tight.solder another wire to a washer under one of the engine mount screws .attach these to your onboard battery or rca type jack