We have exhausted all options (except the return line solenoid valve that was mentioned....still waiting for my manual to determine if this common rail design has one) except yanking the pump. There was no air in the system, purged via external electric fuel pump, no codes that are not surprising (large leak and rail pressure low) we got lots of volume into the rail but no pressure was built. There is something causing the "high side" of the injector pump not build pressure. The possibilities are as follows:
1) Debris (locktite) causing a valve (cascade overflow valve) to malfunction and not allow pressure to be built in the three piston radial pump high side
2) Solenoid valve is operating incorrectly. As per a diesel testing facility, "the solenoid valve operates like a high frequency valve on a gas engine (not the same function but similar action) it opens and closes at a high rate dependent upon the ECU's commands". If it fails entirely it can cause a no start, as previously posted by another member, and is difficult to diagnose without a test "bench". We pulled it out and it opened and closed in very rapid succession (vibrated) when the engine was cranked - what does that prove....absolutely nothing. I thought about just replacing it but it costs $465 and the testing of the whole pump will be conclusive and less cash.
3) Elusive return line solenoid staying open and not allowing pressure to build. I would love this to be the case!
4) Pump shaft failure (common in Duramax) but very unlikely
5) Hung up radial piston(s), broken return spring/broken piston/seal damage, in the chamber not allowing pressure to build. The high pressure piston ride on a tri-lobed cam and are forced to the periphery with every revolution of the shaft, the are returned to the central shaft via a spring.
6) Who the eff knows?!!!
I really appreciate all of the very insightful replies to this thread, they have help tremendously. I will be removing the injection pump today/tomorrow (late nights make for a weary day at the office) and finding the nearest injection place with the facilities to test a common rail high pressure pump. From what I gather there are only a couple of places in Canad that have invested in the equipment to test these pumps. The local diesel injection service I spoke with commented that most of the manufacturers are heading to CRI but since most pumps/systems are under warranty any failures result in the dealer just remove/replace the unit instead of having it tested and repaired.
Have a great day and I will let you awesome folks know what is up when the next step happens. BTW I will post some pics of the timing belt/pulleys/injection pump removal. HAVE A GREAT DAY!!!!
MIke
