Dd15 crank no start

[PROMOBILE]

I have a 2012 DD 15 that we have a crank no start issue. The truck came in for a lube oil filter, and after changing all the fluids and filters we found that the truck would crank, but no start tried putting a purge tank on it to purge out the air and still crank no start. Upon taking apart, the three filter fuel system I found that the check valve was bad. Tried to get parts but ended up replacing the fuel filter housing to a two filter system upon doing so still crank no start performed a fuel integrity test, and found that it had no low side pressure. We then therefore replace the injection pump and low pressure pump. Still crank no start still zero psi on low pressure side 275 to 325 bar on high-pressure side we then replaced injectors and it fired for about 10 seconds then shut off and again crank no start no low pressure. We are kind of at a loss with this thing.