Glow Plug won't light in cold weather (MB 240d)

[ifthecar]

Hi,

My 1974 240d's glow plug was working great 2 days ago when the temp. in DC was around 34-36 degree F. Then yesterday we had a snow storm (1") and the temp. dipped into the teens (around 15-18 F). The car is also left outside.

Now when I try to warm up the glow plug (pulling on the knob), it won't light up even after 1 minute of pulling on the knob and my car won't start. Today was the first time the temp. increased to around 32 F, but the glow plug still won't light up.

Why won't my glow plug work.