Fuel System Test Gauges A ' E Hand Tools introduces two new products under its Star Products brand: the Fuel System Pressure Test Gauge (P/N TU-32-20) and the Fuel System Restriction Test Gauge (P/N TU-32-21). These test gauges are used to test either pressure or restriction on diesel engines with Compucheck test ports. Assemblies fit fuel systems of Cummins and other diesel engines that have been outfitted with the Compucheck test ports.