The oil pump should be directly driven inside the engine.  If the engine is running, the oil should be pumping.  If the oil pump was not working, the engine would not have run "seven to ten minutes".

What you are probably hearing is all the internal engine damage done when the old pump quit.  At the very least, you need a set of crank and rod bearings.  The noise lessens when the engine warms up and rod knock/piston slap is taken up by the heat expanded parts.

Did the shop recommend any additional work when you brought them the vehicle with the bad oil pump?

Did they replace the oil and filter when they did the oil pump?  If so, they should have used a quality filter with a check valve, not recommend that you get one now.

The sending unit may be just fine, but the ruined bearings are leaking oil pressure and not allowing a proper pressure to build.

It's tough to call without seeing/hearing the vehicle, but I think I called it right.

Anyone else?
(edited fer spellin'!)

The oil pump is mechanical and is usually either a go or no go situation, they are usually not intermittant.

The oil light or gauge is consistantly indicating low oil pressure for first 10min of run time???

I would purchase a new mechanical oil presure gauge ($20 at auto parts store) and replace the factory electrical oil press sender with the new mechicanical sender.  Least then you'll know where you are at with the oil pump.

The rattling noise on start-up is the lifters, ya know those little things rolling on top of the camshaft and connected to the rocker arms. Not the piston or rods.

Rods don't ever get quieter, if their knockin' they will only worsen and get louder until they fly apart.

IMHO, the mechanics are not up to snuff or they'd have checked it before ya picked it up, sounds to me as if they installed it improperly and it's having to be primed in order to get started to pumping. Possibly mis-installed pick-up tube, either way makem' fix it!

Mike

Your oil pump consists of a drive and driven gear. the driven gear slips over the crank shaft and is turning whenever the crank turns.  It is an all or nothing proposition. You may have a problem with the pick up tube or a blockage in the oil passages, but like others have said, if it ran for 7 to 10 minutes and did'nt lock up, it had to have gotten some oil. That engine does'nt have lifters, the rocker arms rest on the cam lobes. Toyota oil pressure sending units are very vauge as to exact pressure. I have customers ask all the time "is'nt the pressure to low at idle ?" If this happened right after the repair it is possible that the pump needed to be primed and was sucking air and oil. these are noisey engines when little oil is present, timing chain, rockers etc. A filter with a check valve (I use only toyota filters on my trucks) does help keep the oil in and around the pump or at least holds oil ready so the pump does'nt have to bring it up from the pan. I am a Toyota master tech and have seen similar things, but then again I always make sure to pull the EFI fuse and crank the engine for a few moments before I actually start it after the oil pump has been off.