Shutdown Problem

[SteamDave]

I've been a member for a while and I've finally decided to post this. Nobody can tell me why my truck is doing this so I'll try my luck here. My problem is the pin that shuts the engine off, (under the solonoid) keeps tearing a corner of the rubber tip partially off. This keeps the pin up off of its seat and won't let the engine shut down. I have put 3 of these things on the truck and within a month the same thing happens again. At $90 a piece- thats the whole assembly, solonoid and all, this is getting EXPENSIVE!! Before anyone asks, there is nothing in the hole, the piece that breaks is still partially attached and comes out with the pin. I can't see anything in there that would cause a new one to tear. By the way if you havent figured it out, I do ALL of my own work. Any help/suggestions will be appreciated as I hate to have to keep stalling the engine to shut it off.