Seems to be some disagreement about the ball and spring and also several misunderstandings on how the pump actually works. The Roosamaster/Stanadyne DBG pump is two pumps in one. It has a rotary bladed vane pump that sits in the back. It is a charge/feed pump that delivers low pressure diesel fuel to the other end where high pressure pumping takes place. That high pressure is done by two small pistons. So a low pressure rotary pump is feeding a high pressure piston pump. The low pressure feed pump has a pressure regulator set at 60 PSI. The ball and spring you mention is a "housing pressure regulator" set at 4-6 PSI. One pressure works against the other. If that ball gets stuck closed - the internal pressure will rise until it gets to the same PSI as the charge pressure. When that happens with 60 PSI against 60 PSI - all flow stops. Then the pump starves for fuel and the engine will not run.
To anyone who says they removed the ball and all was fine? Did you recheck the timing advance curve after removal (if equipped)? Just because the engine still runs does not mean it's right. Let's say a typical Deere is set to have the timing advanced by 14 degrees when the charge-pump reaches 60 PSI. If you remove that ball - it lowers the housing pressure by 4-6 PSI. This works the same as raising the charge pressure by 4-6 PSI and the result is the timing advances too much, too soon. That if the pump has a hydraulic timing advance. On older pumps that do not - removing the ball just drops the housing pressure to zero which does not affect much in regard to running. I think Stanadyne wants some internal pump housing pressure to eliminate dirt intrusion. I.e. slight pressure on the inside pushing out.
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