Good chance it's on the side of the engine , are you able to see the valve cover , from the access panel in the bedroom ?
This picture shows it , below the red circle , that would have been a manual fuel pump for priming the fuel system.
Could also be visible from underneath, just past the air compressor.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.