Hmmm... interesting reply with little substance. You disagree based on what - emotion? I've been a diesel mechanic for forty years, and have been working on Stanadyne/Roosamaster systems since the 60s. I also worked in a pump shop as a pump rebuilder for CAV, Bosch, and Stanadyne/Roosamaster pumps and injectors. In regard to the 6.2s as used by GM, I've been working on them since they came out in 82 - at a professional level. I also own quite a few. Now, that doesn't mean I'm never wrong, nor do I claim to know everything. I am also not well trained with the new common-rail and computer-controlled direct-injection systems since I'm not in that business anymore. That being said - everything I posted is accurate.
The DB, or DB2 rotary pump does not even need injector lines hooked to it to pump fuel. When rebuilding them, very often we'd first test them with the lines off - with just the feed-fuel hooked up. When you crack the injector lines, you speed up the process of getting the lines filled with fuel since the opening pressure of the injectors is not involved - but - it will happen anyway - withtout cracking the lines. The only way that pump gets air-bound is on the inlet side. Fuel from the exit side of the pump comes from the high-pressure plungers that can easily generate 10,000 PSI -and will pump fuel at zero pressure or 10,000 lbs. of pressure - but of course - at zero if will pump faster, and therefore the lines get full faster.
To put it simply, the basics of the DB2 pump are - it has a little low-pressure fuel pump (vane type) hooked to a plunger-type high pressure pump - all in one unit. If the low-pressure pump (on the inlet side) gets air in it, it won't be able to pump fuel to the high pressure side. But, once it does have clear fuel with no air-bubbles in it - and the high-pressure plungers are getting the fuel - there is nothing beyond that point that you are going to do - that will hamper fuel flow by air getting in.
If you were to run out of fuel - out on the road somewhere. All you have to do is get the air bled out of the inlet side of the injection pump. That, because the injection pump has it's own low-pressure fuel pump built into the back of it. It is a four-vane type pump and will not work well until all the air is out of it. Thus the need for bleeding. On some applications, those pumps are used with no other fuel pump other that one inside the injection pump. With the Chevys - at least with the 6.2s, GM was nice enough to add the separate mechancial fuel pump on the engine to make things work a little nicer (and later, an electric pump). On the Chevy Chevette diesel - they didn't bother - i.e. no external fuel pump. I've have installed pumps on many mechanically injected 5.7s, 6.2s, and 6.5s and got them started with little trouble without cracking the lines.
Since you guys out there are telling me I'm wrong - please explain, with a few accurate facts.
Not that I have professional diesel repair/service to back me up, but my 6.2 would not even hint at starting until I had 6 of eight lines dripping fuel. Even then it ran pretty rough for quite a while before all the air was gone.
