once on my previa van the starter stayed engagedeven when i pulled the key out and the only way to stop it was to disconnect the battery. upon inspection of the starter the plunger was heavily pitted which are signs of resistance and it seems that the plunger fused it self together and the return spring was'nt able to disengage the plunger. a little turning on my lathe, cleaning the contacts on the plunger and replacing the other side solved the problem.