Would it cause a fuse to blow ?

My pump is knackered i think , as pedal goes hard after ive been driving around for a while ,its done this for a while but is somethimes ok , but as some of you already know , had alot of engine parts off , cleaning etc , now when i connect one of the main plugs onto pump , it blows this fuse why would it do this peeps , got a multimeter but whatr kind of readings should i by looking for , the plugs has 5 pins if i remember right , so cant put it in the wrong way

thanks again

hate electrics man !