It's noted that you have a leaking hose on the #5 injector, however, this has nothing to do with the failure to start.

Furthermore, the check for resistance at the glow plugs will probably not yield you anything if the fuse or the relay has failed.

Tomorrow morning, when it won't start, put a voltmeter on the #1 plug and see if you have 12V when you first turn the key to the #2 position.

A good foreign auto parts place might carry them, but MB surely does. I have purchased a dozen or so of them over the years. Same with the hose material. I keep a meter or so on hand because when the stuff ages and begins to crack it leaks right through the cloth covering, making a stink and mess. So if you find them, buy a few of them to keep them on hand. Good luck, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1985@@1985&makeid=MB@@MB@@X&modelid=300-TDT-001@@300TD+Turbo+Wagon&catid=D@@Diesel+Injection&subcatid=D1040@@Diesel+Inj.+Plug&applicationid=000004617&mode=PA

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1985 Euro 300TD Turbo