1991 7.3 diesel

I have a 91 diesel in a 350 - i have just started hearing a grinding noise coming from inside the oil filler cap - sounds like a loose bushing or something around the timing chain - not a pulley or water pump (but thats the noise) - anyone know whats going on with my motor?

Thank you!!

There is no timing chain, it's all gear drive, and they can get pretty loud. You have three gears, crank, cam, and Inj pump drive. Just like it should be (chainless). The Inj. pump gear bolts may have come loose, pull off the oval cover/oil fill on the front of the upper gear housing and inspect the three bolts. One may be griding on the housing.