My engine started knocking after low oil pressure

check your oil level, color, and smell. My guess is that the low oil pressure light is on because of literal lack of oil to pressurize. Generally when you get that light and a knock it points to major engine repair or replacing the engine. Knocks due to oil pressure can indicate many things from a bad head gasket to a stretched rod or blown piston rings. Check your coolant reservoir for signs of oil entering the cooling system as it will float on top of the coolant. By the sound of it it needs major mechanical repairs

if you ran out of oil and you now can hear knocking sound comming from the engine then it time to get it checked by a mechanic

Sounds like a tapping maybe lifter. Maybe valve check under valve cover.

Worn bearing caused by a defective oil pump or low pressure due to leakage around the worn bearings. Either way you need to overhaul the engine.

Knocking in engine and low oil pressure usually means bad main bearings. May have been caused by bad oil pump or just worn out bearings due to high mileage. If this is problem needs engine or rebuild old engine.

Dosent sound good. Oil light on means you lost oil pressure. and the knocking sound is the damage done due to low pressure. Start looking for another engine or another van.

did the oil light come on? it it did that means a low pressure situation which can cause con rod bearing damage. the knock sensor can cause that too.

i'm sorry! does the engine dipstick for the oil,is it full? has it been run low on oil lately? is the knocking sound like a real hard knocking,thumping with like deep base sound?if so,do not start it again. you may have a bad crankshaft bearing,or a bad crank,broken crank. if it's a tapping sound,that's different. it could be low oil pressure, just like the lower knocking,it may be bad oil pump.my advice is this, lower knock from oil pan where you drain the oil,do not start! upper,on top of the engine,just change oil 1st add a fram oil filter,if in cold weather recommend 5w30weight oil,in summer,30weight castrol with fram oil filter.is your oil light on? if not,then it'not low on oil,but CHECK your oil on dipstick,just to be sure thank you for choosing fixya.com

Does the oil light come on or the knock occur during the engine warm up after a cold start?
There could be a couple of problems causing the issue. You could have an oil pressure pump or pump pressure regulator sticking. I would have a mechanical oil pressure gauge installed and verify oil pressure at idle and 2500 rpms to make sure oil pressure is in normal ranges.
You could also have excessive piston rod bearing, crankshaft bearing or cam shaft bearing wear that will cause oil pressure to drop too low to prevent the rod knock your hearing at 2500 rpm.
You said a knock and not a ticking noise,so I don't believe a lifter is the issue at 2500 rpm.
Start with the oil pressure check and go from there.
Let me know.
Regards,

how low does the oil pressure drop?? is it below 40?