I use a [link=http://sonictronics.com/xcart/customer/product.php?productid=16152&cat=305&page=1]metered glo plug ignitor[/link] to check for bad plugs. the meter tells if the plug is bad or not but its hardly ever reliable...when ever the meter is in the red, it 98% of the time means the glo plug ignitor battery died.

just my $00.02