Well, no fuel, no start. Leaking air into the system means lots of cranking to displace the air. The starter turning the engine over is the most inefficient fuel pump you can imagine. Thus the hand pump.

Check all the jumper hoses between injectors, the lines bringing fuel from the tank (there is a short, fat hose from the hard line from the tank that can get old and crack, and weep fuel/leak air), and your hand pump. Also check back at the rear of the car from the fuel tank, where there are a few other rubber lines subject to aging cracks.

The injection pump is a positive displacement pump. If you get air in it, it basically stops working correctly as it cannot generate the pressure needed to pop the injectors. The hand pump, while also not the most effective pump, is the designated device to clear the system of air. It is a piece of junk and has to be reasonably tightly screwed down. If it leaks fuel out, is will also allow air in. Not good.

There is an aftermarket hand pump that is less prone to leaking if yours is really the source of the problem. But be thorough when you inspect the vehicle. Until you get the system air/fuel tight, you will have difficulty as the starter is going to be worn out along with the battery performing this air purging task every time you start.

As for temperature contributing to the problem, the system is made of a bunch of dissimilar materials and they all have different expansion rates. The rubber O-rings in some places can handle this fine until they become aged and stiff. Cold O-rings are characteristically stiffer than warm ones.

So, make sure everything is sealed up. Sounds like you have done everything else. Jim

__________________
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)