I have a 1995 Mercury Grand Marquis Runs good except sometimes it won't start. It'll crank just fine but that's it. I unhook the battery for a minute and then it starts right up. Works fine for a week or a day, then won't start No check engine light.
When it doesn't start, switch the EEC relay under the hood with a different relay of the same part number to see if that fixes the problem. If it doesn't, check to see if there is spark and fuel to the engine when it won't start.