[Shiny]

Thanks for the explanations. I apologize, but I'm still struggling to understand the pressure at the carb inlet when an electric pump is in series with a stock mechanical pump and there is low fuel demand.. (at idle).

Originally Posted by glhs#116

...On the other side it produces pressure to the carb that it regulates to whatever pressure....

This is the part I'm trying to understand. The term "regulate" is more like "self-limiting" I think. Because the pump is all diaphragms and springs, is the max pressure it can put out imited by the diaphram spring in this image:



But isn't the max (idle) output pressure of the mechanical pump always relative to the inlet pressure?

Similarly, doesn't an electric pump build pressure at its outlet when there is low flow at idle (or dead-headed)? It may be internally regulated or limited but I have to believe it is going to be 5-7 psi, correct?

So if the pressure above atmosphere (which is what a carb cares about) is 5 psi at both the outlet of the electric pump and the inlet of the mechanical pump, how can the pressure at the carb not be the sum of both "dead-head" or low-flow pumps?

I think I am missing something here about how the mechanical pump works because no-one on this thread has mentioned flooding at idle because the pressure got too high.

I think if someone measured idle inlet pressure at the carb with and without a series pump powered, I'd at least see whether the two pressures added or if the mechanical pump somehow delivers the same output pressure regardless of inlet pressure.

Mike