Focus 2.0 tdci 2006 - Focus 2.0 tdci glow plugs - minioneman

The glow plug light on my 2006 focus 2.0 tdci only stays on for less than a second even in the coldest of mornings. It allways starts but takes a fair amount of turning over before it fires. I have also got a 1.8 tdci and the light stays on for up to 5secs and starts much better. Is this normal??