A Land Rover glow plug is only available if you have a diesel engine installed. Essentially, this is the diesel version of the gasoline engined spark plug, and although they work on different principles to ignite the fuel in your cylinders, they accomplish the same purpose. Every Land Rover diesel engine will have glow plugs, and every glow plug can be tested by using the multimeter method.
Open the bonnet of your Land Rover and locate the glow plugs. They will be in virtually the same place as spark plugs would be in a gasoline powered engine; just find the glow plug wires and trace these to the glow plugs.
Remove a wire from the top of the first glow plug to be tested. Use your spark plug boot pliers and grasp the wire firmly on the boot where it meets the top of the glow plug. Pull firmly and twist if needed to remove the boot and expose the top of the plug.
Set your multimeter to read ohms, and then touch the probes together. When the probes are touched, the multimeter will give a "0" resistance reading. This is exactly the reading you want to see when you test your glow plugs.
Touch the black probe on your multimeter to the engine block. This will act as the ground. Touch the red lead to the tip of the glow plug you are testing. The resistance should read "0," and if it reads anything more than that, the glow plug is bad and needs to be replaced.
Continue testing each of your Land Rover glow plugs. If you find a bad one at any time, it is recommended that not just one but all need to be replaced at the same time.
It is also possible to remove all of your glow plugs, keep them wired while turning the ignition on and watching the tips to see if they glow, if not done properly, it will be a fire hazard and can result in severe flesh burns.