[justpassinthru]

I have seen a lot written about this but no explanation of how it accomplishes it.

I am confused with how adding or removing shims to the fuel pump increases or decreases fuel pressure.

It would seem to me that by doing this, it would just move the stroke into a different position in the pump. How would that change the fuel pressure?

For example: Lets say there is 0 clearance or even compression between the push rod and the pump lever when the pump shaft is on the base circle of the cam lobe.
If I were to add a shim between the pump shaft and lever, I cant see how that would increase fuel pressure. Just the diaphragm position would be moved and the stroke would stay the same.

I could see that creating clearance between the pump shaft and pump lever would lower fuel pressure due to reducing the stroke of the pump along with making a noisy pump.

I just don’t know how, by doing this you could increase fuel pressure without increasing the stroke.

Please enlighten me.
Bill