The 1980 300 SD glow plug cycle has just changed how long it stays on. Does this indicate that one or more of the glow plugs has burned out?
Is there a test to determine if a glow plug is burned out? On my 7.3 Navistar in my Ford truck I use a test light hooked to the positive side of 12 volts and touch the connctor point of the glow plug. If it lights , the plug is working. It may not be working 100%, but it is getting warm.
Would this same test work on these glow plugs?
1980 Mercedes 300 SD
1994 Ford F-350 7.3 liter turbo diesel
1993 Chevy Suburban