Oil Pressure on Discovery 4

If your oil pressure light was on, but the oil level is OK on the dipstick, it seems that the engine lost oil pressure due to a failed pump (a rare thing to happen) or a blocked filter, or sludging in the engine.

The first thing to do is replace the oil pressure sender unit with a pressure gauge, and idle the engine for a few seconds to get a reading. If it reads zero, the engine may already be damaged. That loss of power sounds like the engine was beginning to seize.
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Sounds more like an engine idle issue than a oil pressure issue. If the engine idle drops too low, the oil pump cannot provide sufficient oil pressure. If there is no oil light when the engine is idling normally, then there is no problem there.

This question is not understood Sir. We need more and complete information

Take out the oil sender switch and fit a gauge , if the gauge reads low the pump relief spring may be broken or it could be stuck . the oil pick up tube filter could be blocked if there is a lot of sludge in the oil pan,

I agree with the oil pump. Drop the pan and replace it. Just because you had a slow roll that would not effect oil pressure. Make sure you torque the pan to specs, very inportant.

Pull the oil pan and check the oil screen first. It may be plugged up
This happens when the engine is not serviced and neglected

Drop your oil pan and remove the gasket, You will see your oil pump under your crank shaft. You will be able to remove it from here

If you want to test the oil pressure sending unit, let me know. I can assist with that.

It could be that your engine oil pressure is indeed low -- how many miles on the engine?

I had this problem on my gto i turned out it was the wire from the oil pressure sender unit , it was all corroded with oil and ready to snap off , try the wiring first and if its not that then the oil pump is on its way out.


john

check oil pressure with test gauge from near large engine oil filter and cooler assembly, to rule out sender unit issue, if same readings check oil pick up sucking air O ring leaking?
releif valves in oil filter cooler assembly, stuck/jamming open?
if vehicle has been sitting for a couple of days and this happens light should only stay on 1-2 seconds go out and then gauge starts reading
have seen this on older higher km vehicles bad ones have balance shaft centre journal in sump worn out (new sump)