Glowplugs are used in diesel engines to warm the combustion chamber prior to cold starts. Without the assistance from these plugs the diesel engine, which relies on heat generated by compressing air rather than a spark, would have trouble starting under some circumstances since a cold engine block draws the heat away.
Glowplugs can fail due to poor quality or excessive use. Sometimes a glowplug relay may be the issue and not the glowplug itself. Have your vehicle inspected by an experienced mechanic if you're unsure.
Replacing glow plugs should be a relatively simple process, similar to spark plugs. Consult with an automotive service manual for your vehicle for instructions, or contact a professional technician.
We stock and sell a wide variety of quality glow plugs from these manufacturers: