WARNING: This page is about a different car, the 1984 Volkswagen Rabbit, 1984 Volkswagen Quantum, and 1984 Volkswagen Jetta. However, it is still accessible from the selected car via links, so may be relevant.
Listen to nozzle while it is being tested on special testing gauge (US 1111). Use long, slow strokes of testing pump lever (1-2 strokes per second). If nozzle is working properly, it will "ping" as fuel emerges.