Samurai starts and runs then after 30min running will die and will not restart. I have replaced coil, replaced sparkplug and coil wires, checked continuity and cleaned wiring connections to distributor, coil, alternator and ballast resister. There is power to coil even when it won't start but no spark at the plugs. Could it be an intermittant problem with ignition module in distributor? Not sure how to test that. Any other ideas of what to check?