Olde Mazda diesel water tap
I drive a 1984 4-cylinder diesel Mazda pickup. Plain vanilla, still cheap & reliable. On the driver's side, snuggled within the chassis, there's a small spigot with a knurled knob. When I bought the truck the dealer (long gone) told me it was important to periodically "drain the water off the diesel fuel" by opening the spigot. I've done this a few times in the 2+ years I've had the truck, but nothing ever comes out. A reminder label on he door jam tells me bad things will happen if I don't drain the water out. I've asked two local grease monkeys to troubleshoot the problem, and they are comatose. A month ago a dash light that looks like a faucet started glowing. I opened the spigot up again, and no liquid. Truck runs fine.
Should I just forget this "problem"? If not, what do I do?