Hi

My glow plug light is fine when first start of the day, goes out when heated etc, but then the light will not come back on at all during the day, no matter how many times i start the car again and again (Taxi driver) The car still starts no problem at all, just no light on at turn of key, any pointers anyone ?

Andy

sounds like yours is working fine then !!!
if only we were all that lucky

how long should the glow plug light stay on before starting???

Strictly speaking a diesel engine shouldn't need glow plugs as it is the extremely high compression that causes the fuel/air mix to ignite. However, in order to give comparable starting characteristics to petrol engines, glow plugs are used to heat the air in the cylinder resulting in quicker ignition. A modern diesel will typically only require the glow plugs for the first start of the day, residual heat negating their requirement thereafter; winter conditions may see glow plugs staying on for longer (still just seconds) or being used at other times in the day. HTH.