I have a 1980 280ZX with 38000 original miles. After starting cold it doesn't register oil pressure until the engine warms up. So far I have replaced the sending unit and pressure relief valve. The guage reads erratically. I installed a mechanical aftermarket guage and got a reading of about 5 psi warm and 0 cold. I disconnected the guage pressure line at the block and had good flow when warm but just seepage when cold. I will replace the pump next but think that I probably have a clogged intake screen. Can the screen be checked/cleaned without total engine removal? I would appreciate any advise. Thanks.