The only part bad on my 1040 was the fuel level sensor. I had read there was a recall on the original part and a replacement was issued. I could not source the new part anywhere so I found the original on fleebay and its been working fine for more than a year.
Original Fuel sending unit part: A026J499 or Nsn 6680-01-651-7526
Replacement model number A054f059. When i tried to order at cummins it was out of stock. This is pre pandemic btw.
Ohh, before I forget, you have to tear down half of the unit to get to the sender.