I recently was advised to check for spark by using a timing light. I had a no start in cold. I hooked up the light as usual and had someone crank the engine - no start - no light. I thought no spark. So I pulled the plug and grounded it - got spark. So did I get the wrong idea about using the timing light to check for spark? Was there not enough current to run both the light and crank the engine at the same time?

There should have been enough power to do both, BUT there are zillions of different timing lights on the market and some might be more sensitive to the power drop than others. I have used the trick a number of times with my car and the timing light. Another approach is that you can also get a little device that goes between the wire and the spark plug that checks for ignition, if that light does not light, then you definately have a spark problem.