CM2350 Code 4727

[windowrattler]

Figured I'd update the ending of the story. We ended up putting in the fuel pump actuator. After this the driver reported fuel mileage back to normal and the code would pop less often but was still there. I racked my brain for a solution. I poured through some cummins training documents and found my culprit. The fuel actuator doesn't mount into the fuel pump head, there is a fuel actuator adaptor/block. In this block on older ISX's (2250 block we had around) there is an venturi air bleed. On the later years it is a small 300 micron drilled hole. In the XPI training slide show it specifically points out this small passage and that when blocked it could cause high rail pressure codes during engine decel. We replaced this block and the issue is resolved.