As long as you have enough compression in the cylinders glowplugs are unnecessary period. It will just take a a few seconds to crank. My old 300SD takes about 45 seconds of cranking on a warm day if I bypass the plugs. If you have poor compression good luck. If the plugs are not working or you start cold you will feel the weakest compression or coolest cylinders miss for a bit before the engine gets warmed up.

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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