Our under the counter dishwasher is supposed to be screwed into the underside of the kitchen counter top. The counter top is very cheap, some kind of compressed wood. The screws pull out leaving divits in the wood, once we even screwed too deep and the screw poked through the top of the counter, ha ha. The dishwasher is set on the floor. The screws seem to give the dishwasher, mainly when you open the door, a little stability but of course the dishwasher just sits solid on the floor, it is not going to fall over. So, how to make cheap pressed wood more solid to accept a screw, or leave the dishwasher unscrewed? The dishwasher sits snugly between the wooden divides between the sink and floor cabinets.
Some dishwashers have the option of mounting into the cabinets from the side of the dishwasher frame. You might want to check your owner's manual and see if this is an installation option for you.
If not, buy some of the two part epoxy wood filler. Take an ice pick or a slotted screw driver and remove all of the old crumbling particle board. Then mix together enough of the wood filler to fill one of the holes. Fill it in, smooth it out and let it set. When it has cured, use a small drill bit and drill a pilot hole into the wood filler before re-attaching with the screws. It might not be a lasting solution, but it has worked for us in the past.
Had a similar problem with mounting my dishwasher. Most formica counter tops have a particle board base and the front edge is rolled over and hangs down a bit. The front edge hangs about 3/8 to 1/2" below the bed of the counter top. Get a piece of 3/8 or 1/2" fir plywood 2" wide and 6" long and cut it in half to from 2 pieces 2"x3". Mark the bottom front edge of the counter with pencil where the dishwasher should be mounted to the counter top. Use wood glue or construction adhesive and place each piece of wood on the bottom of the counter top against the front edge overhang centered with the pencil line. Apply a couple of clamps to hold the wood blocks in place while the glue dries over night. Be sure to use screws that are 1/2" to 5/8" and this should solve your problem.
