I found this info at ask.com which led me to a trucker's forum.
Bleach will harm any kind of engine, both gas and diesel. Not only the engine, but all the lines from the fuel tank, and the fuel tank itself will corrode upon contact with the bleach. The effect is almost immediate to the tank. When the engine is started, the effect is almost immediate to the lines. Basically, the carburetor, or the fuel injectors will become clogged up very quickly, and the lines as well. EVERYTHING from the tank to the carburetor/injectors will have to be replaced. It is a nightmare.
One cup of bleach is enough to cause a big problem.
Its funny, people always think putting sugar in the gas tank destroys the engine, when in fact it rarely has any effect at all. Sugar simply sits on the bottom of the tank, rarely flowing out, and rarely causing any damage. Bleach, on the other hand, is a sure fire catastrophic killer.