Hello I'm Chris a Ford Certified Electrical Specialist.
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The focus is notorious for ignition lock cylinder concerns. For a fuse to pop it must be overloaded or touched to ground. A multimeter will be needed to see the amp reading on this fuse before it pops. If the amp is normal then check for a ground connection. To do this, You need to pull the fuse and see what side is 12 volts constant. The other side needs to be ohmed to ground while the ignition switch is turned a couple of times. If it ever shows no resistance to ground then you have found the short to ground. Here is fuse #8 circuit.