this may sound really stupid but how do u know when your glow plug is dead?
plz dont flame me []

To tell wether or not that your glow plug is dead, there are a couple of ways. First way is to take the plug out of the motor and put it in your ignitor. If it glows bright, it's still good, if anything less, it's toast. Another way is to look at the glow plug's element to see if it is damaged or fouled in any way. Hope this helps.