Investigation into fuel system warranty has led to the need to develop cost effective, robust materials that are resistant to both fuel and aggressive cleaners. Acetal (POM) is the current material that is used universally by OEM’s throughout the fuel system for its excellent performance in fuel and relatively low cost, but lacks resistance to strong acidic solutions. Acid containing wheel cleaning solutions are increasingly being used by customers to clean their aluminum and magnesium wheels. Due to the proximity of the fuel modules to the wheel openings, acidic wheel cleaners chemically attack the POM resulting in cracks. FCA worked closely with suppliers in recent years to develop cost effective, acid resistant POM materials that can withstand the stress-cracking at severe acid concentrations and meet FCA’s functional requirements. Other material alternatives that were considered outside of the acetal family provided adequate resistance but had other design and functional issues that would drive up cost. Our study included three unique vehicle flange designs molded in both types of POM and subjected to an extensive acid exposure cycle. The results indicated the acid resistant POM performed more than 15 times better than the current material. However, our validation testing uncovered issues that needed to be resolved before acid resistant POM could be executed into other fuel components such as fuel flanges, valves, and Evaporative System Integrity Monitors (ESIM). In this paper we will compare the material properties and part testing of the current and acid resistant POM.
Monica Shammas, Edward Luibrand, Linda Hess