Patrol oil pressure drop ?

[patroljock]

ZD30DDTi engine - oil pressure light comes on at low revs - after 1500 revs the light goes out - have changed the sensor at a crippling cost of £126 just for the kit of which I only used the sensor and not all the other bits which presumably are for other vehicles - suspect it now may be the oil pump - engine has done 163,000 miles and runs as sweet as a nut - Nissan dealer is quoting me £800 + VAT for a new pump - taking the sump off tomorrow to see if the filter is blocked or sludgy - anybody got any ideas of something I may be missing like a leaky seal etc etc
thanks for reading - hope you can help
Patroljock

 

[briggie]

have you had a look through the workshop manual for any ideas as the cause ? ........ just an idea , hope it hel:thumb2ps

 

[supergnome]

Is this when the engine is cold or hot? If its when cold it may be the pump, and is there an oil pressure releif valve that could be weak? David.