Since my checkvalve was leaking there was very little pressure on the system as the car had been sitting overnight since it was started. I do not know the correct procedure for venting a pressurized fuel system but I would wrap a rag around one of the clamped hoses and loosen it a little to relieve the pressure and catch the fuel.

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Dave
88 300E 250K Sold
2000 C230K Totaled @104K
2003 ML320 156K Sold
2009 E350 4Matic Sport 46K Sold
2011 ML350 60K Sold
2014 GLK350 46k
2012 GL450 55K