There's been a couple of threads lately about oil pumps and as I had an old one sitting on the bench I thought I might put a couple of pictures on just so those that have never had one apart can see just whats inside.
Notice the gears on the left in the pic are wider than the others, these are the return or "scavenge" gears. Being wider they have a greater pumping capacity than the delivery ones so can keep the sump empty, this is why you get the intermitten return to the oil tank, simply put the pump can pump more out than in.
Also take note of the nose of the pump in the far right of the pic, see how it appears to be "eaten away", thats one of the problems with these pumps when they get old. The metal they are made of deteriorates to the stage it starts crumbling apart, when this happens, as has happened with this particular pump, its all over. This pump is past its use by date !
