2 h oil pressure at start up

Hi Brummie pete
Make sure you only use 15w40 grade oil engine has a built in oil pressure sensor to the fuel pump in case of roll over no oil pressure turns off fuel heavy oil when cold takes to long to gain oil pressure so it shuts off fuel when really cold they won't start at all

Regards Old pop

pete,
The relief valve that you are talking about? is it the one on the front of the motor down near the power steering pump.
If this is the case, i had problems with mine because the cylinder it moves in becomes worn over time and the plunger becomes jammed. My oil pressure used to sit on max when revved up.
The local guy tried new plunger with no success. He eventually cut off 2or 3 coils on the spring and oil pressure returned to acceptable limits.
I know your problem is low oil pressure but if this is the valve you are talking about, it could be the problem. My 2H cuts out after an oil and filter change on first start up.
Cheers,
Bros.

Pete,Could be the relief valve at the front of the motor.It is a large nut 20-22?mm behind which is a spring and plunger,it is fairly common for the plunger to wear,causing it to stick in the bore.Awkward to get at,I used a cut down ring spanner borrowed from a mate,and piece of wire to get the plunger out!Could try cranking the motor[disconnect fuel solenoid] if you can control the oil!New spring and plunger were cheap.