Engine shut down.

[jiffy]

I was on a tour and at the first stop it was running fine. When I started up it ran about a half block and just shout down like I turned the key off. I retarded the spark and it started right up. Did thr same thing 2 more times at other stops. Each time I retarded the spark to start and then moved it halk way down and it ran fine. I have read posts about a wire in the dist. shorting out. I have modern points in it. What wire is causing the problem? Thanks, John