1993 hilux

Once I turn the key the glow plugs come on as normal but as they time out and turn off the glow plugs turn back on for a split second and then off again and They do this repeatedly till you turn off the ignition when trying to start. Any ideas?

G'day all, I've been looking around for cars for a while, and found a decent one. This one is a 1993 Hilux with the 2.8 non-turbo diesel (yes, I know they're slow and I won't turbo it) and 5-speed manual. It's got 318,000K's and i know these things are bulletproof so the K's don't matter too...