Intermittent glow plug light........difficulty starting

[calimercedes]

ok i got this 79 240 d auto... its been a week the car is acting up when i start it.. usually youll turn the key on wait for the glow plug light to go off and then start it right? well when i turn the key on, theres no glow plug light, i try starting it then the glow plug light goes on while im starting it. and then sometimes if im lucky it will start, but today it was cold and it just drained the battery and didnt start.. it has the old loop style plugs, the fuse is good, i doubt theres a relay .. is there? so the glow plugs do work, but only when i attempt to start , while its turning over its heating the glow plugs. strange... any help... any ideas????? thank you.