Starts, knocks, stalls

[aaronforprez]

Thank you for taking a look at this.

we have an E-350 with 75k miles.

when the engine temp was lower than 20* the van will crank for 5-10 seconds, start, run for 30 seconds, start knocking and eventually stall. after that you need to get the jumper cables to enable enough cranking for the engine to start running again. at times the vehicle will run for a full minute allowing you to drive away before it starts knocking and eventually stalls.

brought it to the local garage and they said there was no check engine light or other codes they could retrieve. so they changed all the glow plugs and relay as well as replacing the cam sensor (recall item). they said they now had no problems starting the van inside their shop and that everything was fixed. when we arrived that night to get the van, the engine temp had fallen to 20* and the van did the same thing as it did before.

4 weeks later they called and said they were done. i went to get the van back and they gave me a large large bill and said the injectors were losing oil presure and that the oil pickup tube was cracked. the pick-up tube and the pump and the cover were all replaced. but they didn't want to give me the parts back. after a lot of talking they gave me the parts and i can't see anythign wrong with any of them. no crack and no wear marks on the cover or pump.

i'm concerned that they replaced all the expensive items and it still didn't work and then they had to go back to square 1 and found something simple.

the service guy has been less than forthcoming and i really am concerned that i've been had.

my questions-
is the oil pickup tube or gear wear plausible cause for what was going wrong?
will i notice wear marks on the cover from the pump that would cause the problem?
does the cam sensor cause problems that we had relating to cold temperature?
does the type of oil or the weight of oil have anything to do with causing this problem?

thank you all very much for your time.