Oil light on, not low on oil
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Check oil pressure first, Might be as much as a by-pass valve in filter failure or failed sending unit. Oil pressure test will tell you if pressure is up to par, if not, yes I would agree with pump. But also if bearings are wore enough, this can lead to low pressure, an oil leak down test will be needed after oil pressure test. Not a Rover Tech but 15 years experience on Rover and 49 yrs Jag.
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Broken oil pump gerotor
Does the engine make a tick-tick-tick at low idle?
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