One problem related to starter solenoid has been reported for the 1998 Toyota 4Runner. The most recently reported issues are listed below.
While driving to work in my car on 3/21/07 the soleniod of the starter did not disengage and a fire commenced in the starter of the car. Fortunatly, I was able to stop and a passer by,almost immediatly provided a fire extinguisher, and the fire was extinguished. Damage tp the auto was relatively small.