OK
Looking back to something similar.
With cricket bat about to be struck and inflicting pain on Bevis & Butthead both were shown multiple times that you must first pre-fill the filter !
Cos if you don't that and go for a start the LP pump will run dry and not suck fuel--Engine no startee with mucho crankee .
In any case there was always a shop policy to install the WIF sensor and the drain plug FIRST , fill the filter with it sat on a bench and look for leaks before fitting it.
Simply getting these two fools we had to easily install the WIF sensor and doing a half turn to locate it eluded both of them!
They either bent the circular tongue or damaged the O ring causing a leak. On one "You Try" training course Bevis buggered up no fewer than 5 genuine MB filter before he got it right.
Cost of that (AT TRADE PRICE WAS) $220. I got a little testy saying you can teach monkeys to do this.
In your case ensuring ALL the pipework is installed and airtight , the modis operandi is now
1) Remove the suction hose at the filter.
2) With an open gallon plastic container full of fuel sat on the battery ,(trade calls it a dolly can) with 3/8 drop a hose in it (that will fit the suction port on the filter) and then create a siphon filling the filter. The bleed port at the front being removed so that fuel can pour out . Once its pi$$ing out refit the vent plug.
Now with a 14 mm wrench loosen off the HPOP steel injection pipe to the rail and go for a crank watching for fuel being pushed out by the HPOP.
Tighten it up then open #'s 1 & 5 injector pipe and go for another crank. Then see fuel start to be blow out of the first injector pipe--secure it tight ; then crank again until fuel pi$$es out of the back injector connection. Then secure it tight.
Now make sure you have plenty of fuel in the dolly can and go for start ,
After a few cranks the rig will fire and run a bit rough to start.
Once a runner shut it down before you run the can dry , and connect the chassis fuel line from tank the filter.
Now take into account that the chassis line might be empty so with pedal to the metal fire it up and DON"T let the revs drop below 2000 r/m until the plastic lines flow with no foam in the fuel supply.
On the roadside and doing breakdown we have resorted to bypassing some of this after a voiding by running the rig dry.
This is old timer method when I was a teen apprentice in the 50/60's .
Open the filter bleed screw, and with a rag balled up tank filler neck introduce compressed air to the tank with a blow gun forced past the balled up rage. Don't go mad with the air pressure. The air pressure in the tank will force it to push fuel out the bleed port.
Follow the bleed method prescribed, pressurizing the tank and go for a fire up. The air pressure however minimal, and leaking out of the balled up rag will force the fuel into the fuel rail giving you a short cut to bleeding up.
Works every time !
Realistically when someone has broken down with no fuel in the tank and the ambients are below zero and snow flying. Anything is in order to force the bugger to fire up. As it will in your case AND as it did back in zee aulden days up on the Cotswolds fixing a Leyland or Foden truck. All diesel engines in them days had engine driven lift pumps.
Young mechanics these days are spoilt- by innovation.
Bevis & Buttehead had to go --I fired them, no aptitude nor motivation to fix Sprinters .
If you want me to talk to these guys Pro to Pro I am happy to call them and have a quick chat I even have Devlin on hand to make the point more strenuous.
All the best Dennis