Originally Posted by lrg

On your car what ever glowplug(s) are still working should glow regardless if one or more of the others are burned out, only the early cars were wired in series. This really sounds like a fuse problem. IIRC on the 123 the fuse is on the left front fender over the wheel, it is NOT in the regular fuse box. The IP fuse is a flat metal bar, about one inch long and held in place by two screws. There is no covering on the fuse itself but it is in a holder that is covered. Poke around a bit until you find it. Even if the fuse looks good remove it and make sure it is solid and clean. My GP fuse once cracked just under a screw and looked perfect untill I tried to remove it.