I have a 1996 Dodge Dakota 2.5 that keeps blowing the starter fuse. It bows as soon as I turn the key to try and start it. I have never had an issue with the starter before until I stopped and got gas and it just wouldn't turn over any more. I had the starter tested and was told it was good. I found the 30A starter fuse was blown and changed it but the new fuse blew too. Don't know where to look.
If the fuse blows with the ignition switch on before you even try to crank the engine, that's not in the starter circuit. Look for a wiring harness that fell down onto hot exhaust parts and is grounding out. If it blows when you turn the ignition switch to "crank", remove the starter relay. If it no longer blows, the starter solenoid is shorted, (extremely rare), or the smaller wire going to it is grounded.
A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a 12 volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.