2.) Damaged cables of motor and button have been found for Pump no.1 & no.2 respectively. - This can mean 'Damaged cables of motor for Pump no.1 & button for Pump no.2 have been found."
Unless I'm restricted in the number of words to use, I would use sentence 1 and sentence 3 to avoid possible misunderstandings.
2.) Damaged cables of motor and button have been found for Pump no.1 & no.2 respectively. - This can mean 'Damaged cables of motor for Pump no.1 & button for Pump no.2 have been found."
I see connflicts in logic with this sentence. First, "damaged cables were found" sounds like they were lost. and now someone has found them. If there were pump motor problems caused by the defective cab