Don't know if this has been discussed here before, but my 2004 2.7 developed a problem on start up recently. Basically it would fire then die and refuse to start for ages. When started it was fine.
Cut long story short, was advised that the "O" rings on the low pressure fuel lines start to fail, allowing air into the fuel line which can been seen in the clear fuel pipe near the high pressure pump.
This has been discussed a lot on MB forums as its a common problem for vehicles at this age now.
A pack of genuine MB "O" rings of e-bay, there are 6 in the pack but only 4 to change on the jeep and she's working fine now