This isn't exactly a fool proof test but it might give you an idea of oil pump health =>

(get some rags to mop up first)

At idle with a low pressure showing on the gauge open the oil filler cap and see if you can see any oil being sprayed inside. A healthy oil pump should be pushing quite a lot of oil through to the top of the engine - with a decent bit of diesel blow-by you should be able to water proof your neighbour's fence!

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!