ISX Oil Pressure Problem

[United340]

Good morning everyone ,

I have a Cummins 870 I rebuild . I’m a former freightliner tech with Cummins certifications from 2010.

I just did a 870 rebuild
About 6 months ago… using {non-oem} parts.

I torque everything to spec n replace everything from rockers , cams , lower bearing , oil pump , cooler n etc.

Customer complain the unit oil pressure would
Drop sometimes from 45-47 to about 25-22 while driving for about 3-4 secs n spike back up..

I personally drive it n it does that . and sometimes does it when u release the throttle pedal ..

I match this issue with a mechanical gauge as well I had plum in by the Oil
Presssure inlet at the oil cooler , the fitting before the Oil filter … it did the same …

Would suspect it to be a oil
Pump problem?

I drain the oil and drip the pan and inspected the pick up tube and the o ring and it was good.. Didt had no metal or heat marks at any of the mains or rods