What else wears in the pump advance mechanism?

[wolf_walker]

Low pressure = low advance.  Gotcha.
Mechanical wear on the advance slider? 
They are shimmed to control max advance I believe, yes?

[745 turbogreasel]

roller axles erode the pump housing.

[vanbcguy]

The vane pump itself wears, that's probably one of the biggest sources of pressure drop.  It gets all the junk in the fuel to it first, scores up the inside and then.....

[fatmobile]

I have a pump with decent internal pressure but still has no timing advance.
 There is a little hole in the piston that lets pressureised fuel into the end of the piston so it can push it to the other side.
 I think that tiny hole gets plugged, so the piston doesn't move.

[wolf_walker]

My pet theory on my funny running, slower than ought to be less MPG than ought to be pickup is the 300+K miles pump that sat for three years and has visible surface rust inside is not advancing dynamically as it should.  I haven't talked myself into coughing up for a
real on-engine timing tester, but my ear and gut think it's advanced too far initially then runs out of advance as RPM demands more.
I think I'm just going to buy a rebuilt pump and quit screwing with it.  Eventually.