When I have the key in the position prior to turning the car on and all the instrument lights come on, the glow plug light does not come on. The engine starts but is horribly rough at idle and sometimes cuts off. Do I need to change my glow plugs? Luckily its hot here.

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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.

i would try to change glow plugs first.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Adiaw 83,

Why doesn't the light works? The symptoms you discribe indicates your engine starts without glowing. So I recommand a search on this site before
replacing anything. It's an expencive experience replacing something on a
MB to find out the trouble not to be resolved!
Good luck and share with us your experience!
Danny

Adiaw,

Do a search on GP. There are many posts on GP in these BBs.

It sounds like you GP are not working at all because of something other than the GP. Do the tests you will find in a search.

P E H