Van Occasionally won't start

Since beginning of the year van has failed to start 5 times. Engine turns over fine, but smells like it gets flooded and acts like no fire. Garage can’t find the problem. They say fuel and spark test fine. Seems to occur when rainy and cool out side. Found if jumped by a running car(14+ volts instead of straight battery 12 volts), van starts, so I am really baffled. No engine codes set and it runs well once started. Could it be the ignition coil acting intermittently? Any suggestions?

How many miles on this van? What year? Try new spark plug wires.

Van has 122,000 miles. Wires and plugs were changed approximately 20,000 miles ago, with a new distributor cap just put on. I guess the wires could be bad.