Ranger starter problem 2.3L year 2007

Hello,
I have a short time a Ford Ranger year 2007 engine 2.3l Argentina, and I have a problem with the start that sometimes starts well and then if I stop the engine in the second game it is longer and when I leave it just without any force and I do not know what could be happening.
I would like to try to make it a refinement and also know how many spark plugs have since I have tried to find a manual and not found. Looking on the Internet say they have eight, but I look at the engine that they only have 4, so I am somewhat stunned, the truth would like to ask you who have the greatest experts on the subject, thank you already ..

Hello if your ranger has 8 bugia 2 by cylinders if you change bugies also change the cables that are expensive controls the preservation of the naphtha pump that also does not turn the fuel to the tank greetings