Just came back from the garage. I pulled the cold start injector out this time.

I tried tightening the hard line connecting to the top of the valve, I put quite a bit of force into it, and got the nut to rotate a bit more. I then primed the fuel pumps twice and checked for seeping fuel at the top of the cold start valve, did not see any, which was a great step in the right direction.

I went ahead and started the car, but only for about 5 seconds, as my air cleaner is off so I can see if it started to leak. Sure enough, after I switched off the engine, I checked the top of the valve and the area was soaked with fuel (top, and sides of cold start injector)

I disconnected the battery, relieved the fuel pressure in the system by loosening the gas cap, and undid the hard line again slowly and caught the excess fuel with 3 folded up paper towels. I removed the two allen bolts that hold the cold start valve into the rubber hose below, disconnected the plug after prying off the metal clip and am going to see what I can do to the conical surface to make it smoother and get a better seal.

The part number is 0 280 170 412 (Bosch part number). It does not appear in any online Google searches so far. There are a couple used ones on eBay, but does anyone know if Bosch makes a replacement part that can be used for this application? The Bosch auto parts website crashes when I input my 1989 300E's data.

Cold Start Valve Part Numbers:
Mercedes-Benz: 0000714137
Bosch: 0280170412
Standard Motor Products: CJ79
Wells: CVS66
Airtex: 6C2066

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)