I just bought a sentra last week, 92 model, it was in a very good condition but problem is at times it wont start, it would just crank, this would happen 1 out of 4 instances, napa carb cleaning ko na siya sa rapide, then next day tune up sa servitek pero naulit na naman

actually nung tune up puro kalawang na yung fuel filter, isa ito sa pinagdududahan ko, how much po ba sa palinis ng gas tank,
o may iba pa kayang cause, kasi minsan one click naandar na then pag pauwi ka na from the mall patay ayaw umandar, kailangan may mag start ng key then choke ko yung carb

please advise, thanks in advance