Your car is a pin type glow plug system. The glow plug relay uses number one glow plug as a temp sensor by measuring the current through that plug to determine when to turn off the dash light.

Start troubleshooting by putting a voltmeter on one of the plugs. If there is voltage then replace all four plugs. If there is not voltage, check the 80Amp bar fuse in the relay. This fuse will often look good when in fact it has vibration caused stress crack that is difficult to see.

If the glow plugs work okay, but the dash light still does not come on, check the bulb in the dash light. Remove the kick panel below the steering wheel and reach up with your hand and push the instrument cluster toward the steering wheel to get it out far enough to access the lamp.

Good luck,