Outer Limits 4x4 Board

Up until about a week ago my 06 RA diesel would start straight away even on the coldest of mornings. Now first thing in the morning it is really hard to start. It cranks over for about 5 seconds before it finally fires, then for the rest of the day now the engine is warm it starts straight away. To me it sounds like it is the glow plugs are not working. Can someone go through the process of checking the correct operation of the plugs.


Thanks Matt