Thanks to each of you for taking time to respond.

My car is a 1987 300E with 160,000, I have driven it for 8 years. Fist time it failed to start I took it to the MB dealer, they replaced the fuel pump and OVP relay. I left the shop and got about three miles before it cut off at a stop light. They came to pick up my car and it cooled down and started before they loaded it up. They kept the car for two weeks and said they could not get it to repeat the problem.

It has happened (drive a short distance and fail to start) about a dozen times since 2003, sometimes 8 months between episodes. In the last week or so it has become hard to start, and cut off once about a mile from home. I have replaced plugs, wires and cold start valve in the last six months.

Where is the crank position sensor and OVP relay located and what do they look like? Thanks, Steve