The distributor vacuum advance module adjusts the timing of spark in the cylinders of the engine. When the internal diaphragm of this module ruptures it prevents that proper timing from taking place and the engine will begin to over consume fuel. This over consumption will result in excessive engine temperatures, vapor lock-like symptoms, and frequent shut downs after the engine gets hot. Recommend to replace this every 1500-2000 hours. Found on the Nissan A-15 engine.