how do i fit glow plugs to my 1977 Citreon Xantia TD?

You could well be right - but its as well to check them first, using a multimeter set to the 'ohms' or resistance scale. Take off the heavy wires to each glowplug, and connect a meter to each one in turn, with the other meter lead clipped to the engine as an earth. You are looking for a resistance of about 1 ohm only on each one...a high resistance or no circuit means that they are faulty. Also check that you are getting a 12v supply to the plugs with the ignition switched on,after you have connected them again. If you find a faulty plug they simply unscrew, but access can be difficult. Don't force them as they have been known to snap off, which is a real bore.

John
January 2008