I failed to get a block heater cord last night but fortunately the glow plugs decided to work properly this morning and the car turned over no problem on the coldest morning I have owned this car so far.

Is it possible that this is a short and the cold weather cause the parts that were shorting out not to touch. I've deferred working on the glow plug system fearing it was going to be a big job but maybe it is something simple like a bare or lose wires?

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My Daily : 96 E-300 Diesel with 195,000 miles
Retired: 92 300D 2.5 T 345K miles and for sale
Retired: 95 E320 157K miles and currently parked with blown engine

Both retired cars are for sale as is my w124 shop inventory

First to clear up terminology.

A "short" ( circuit ) is where a power source output terminals are bridged with a low resistance conductor. If you took one jumper wire and attached one end to the + and the other end to the - of your battery, that would cause a "short" and a shower of sparks.

A "open" ( circuit ) is when a wire is not connected and the system just sits there.

One quick test is to attach an _incandescent_ lamp to the glow plug terminal and see if it lights up every time you glow. I don't have a diagram or diagnostic for your system to go any farther.

The longer you postpone glow plugs the worse they get.

Something to think about.

Get them done while they're easy. Get the engine hot and have at it.

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Allen Kroliczek
Oak Grove Autosport | Oak Grove Autosport
01 G500, 82 300TD, quite a few more.....