While I hesitate to recommend any repairs to a 15 year old machine, there are only two possibilities:

1) The intake valve is plugged with corrosion and doesn't allow the machine to fill with water. The result is nothing from the nozzles and a pump that is overheating.........hence the burning smell.

2) The pump, itself, has reached the end. However, I tend to discount this possiblity if you are able to fill it with water and get it to properly work. There is no "priming" of such a pump. The pump sits at the lowest point in the system.

If the problem is #1, the valve is $40.00 typically.

If the problem is #2, it's usually not worth it to get a replacement pump.