I have just came up on this same problem with my 2000 Kia. Turns out it was the Ignition switch. $160.00 to have it replaced.
Big cable from the battery goes to the big post on the solenoid. Solenoid will have two small posts one with an S one with an R. (Start side, relay side) largest of the small wires goes to the start side smaller of the two small wires goes to the r side. if there are three wires hook both the smaller wires to the r side. The larger of the small wires is usually always the start wire and is purple in color.