Lost my cam
To answer your last question about pumps and cams, the pumps use a gear inside a gear type design (just like a trans pump) does.
The high points of those gears pass each other and create an void behind them causing a vacuum and therefore sucking oil up into that void.
As the gears turn further that void starts closing and forces the oil out a different port into the oil filter and out into the engine.
When the tips of those high spots in the gears gets damaged, or the clearance between them gets too far apart they loose the ability to make a seal sufficient to pull up oil from the pan.
The acceptable gear clearances are normally about 1/2 of one thousandth of an inch so if you have metal particles in the oil that are anywhere near or over that it takes material off the tips (high spots of the gears) cause a loss of vacuum as well as a loss of pressure. (more loss of vacuum specifically) which in turn causes a loss of pressure.
This is a big reason why some people can't seem to get oil pressure back after draining their oil.
Just not enough vacuum for the pump to get it's prime.
Here's a pic of the inside of a typical engine type oil pump just for kicks.
Where the gears edges pass each other is where the tolerance can be less than .005 so anything bigger than that can wear off the gears. (keeping in mind that this is not yet filtered oil.) so bigger crap can and does get sucked up and run through the pump.
There are acceptable clearances on the top and bottom of the gear faces also, but for the sake of the length of this I think we can skip that.
Cams and lifters have a hardened surface only, so once the surface is damaged a cam and lifter can wear down really fast because of how soft they are just under that hardened surface.
To answer your last question about pumps and cams, the pumps use a gear inside a gear type design (just like a trans pump) does.
The high points of those gears pass each other and create an void behind them causing a vacuum and therefore sucking oil up into that void.
As the gears turn further that void starts closing and forces the oil out a different port into the oil filter and out into the engine.
When the tips of those high spots in the gears gets damaged, or the clearance between them gets too far apart they loose the ability to make a seal sufficient to pull up oil from the pan.
The acceptable gear clearances are normally about 1/2 of one thousandth of an inch so if you have metal particles in the oil that are anywhere near or over that it takes material off the tips (high spots of the gears) cause a loss of vacuum as well as a loss of pressure. (more loss of vacuum specifically) which in turn causes a loss of pressure.
This is a big reason why some people can't seem to get oil pressure back after draining their oil.
Just not enough vacuum for the pump to get it's prime.
Here's a pic of the inside of a typical engine type oil pump just for kicks.
Where the gears edges pass each other is where the tolerance can be less than .005 so anything bigger than that can wear off the gears. (keeping in mind that this is not yet filtered oil.) so bigger crap can and does get sucked up and run through the pump.
There are acceptable clearances on the top and bottom of the gear faces also, but for the sake of the length of this I think we can skip that.
Cams and lifters have a hardened surface only, so once the surface is damaged a cam and lifter can wear down really fast because of how soft they are just under that hardened surface.