Next time it won't start, might be helpful to check if the spark is good. Since this problem seems to come and go, it may be a wiring problem. Not sure what year your tour is, but there was a recall for some of the older ones to replace wire harnesses. (Check for cracked insulation on electrical wires) If the fuel pump were clogged, I would think you would get some sputtering before the engine died, but it's hard to say for sure.
