There seem to be five (?) topics on this forum addressing the same issue. So far, no one has found a fix to the exact problem; the banjo bolt fuel return is leaking air and there is no sign of air entering the injector pump.

I think we can solve this!

1. Bosch injector pump service manuals have a section on plugging the fuel bypass and all ports. To check for air bubbles, it must be pressurized, then placed in an oil bath. This should show you if there is an opening outside. It is possible, however, that an o-ring could be faulty somewhere on the delivery valve body holder.

2. When I prime the banjo bolt, I can see air coming out. Air comes out, but not as much as when revving it. Despite my best efforts, I do not get the banjo bolt "squeal." I think I should get it. Over time it does encounter some resistance, not all of the air is expelled, but some of it. I can keep that going with air coming out the bypass. Mind you, no air is coming from the supply.

4. There is a possibility that the air is coming from negative pressure. What processes would cause that, and where are the possible points of air entry?

5. Cavitation? It might be possible. Is cavitation a dynamic phenomenon? It is my understanding that bubbles grow and then collapse. I see air bubbles without flow.

__________________
Theseus

Instragram: doss_project
1984 300SD - 930 Blue, OM 617
Murfreesboro, TN

Theseus owned a ship in Greek mythology, and when a part of the ship needed replacing, it was replaced. Eventually, everything was replaced. Is it the same ship? (I own the car of Theseus. )