have an ml270 that has just died on me.Was working ok but pulled out of dri?

Possibly a failed earth cable. As a quick test, get a single jump lead, clip one end to the battery negative and the other end to a good solid metal earth on the engine. If you now get power when you turn the key, you've found the problem. Dont drive the car like this, find the loose/broken earth and repair.
Are you aware that cars with automatic gearboxes should never be towed with the driven wheels on the ground? As your car is four wheel drive I dont think it should be towed at all.

ben888
February 2010