About 30 years ago I installed an RG6466A Deere engine in an IHC TD20C dozer for a customer to replace a tired, and very expensive to rebuild ,DVT573.He was very happy with the repower until 2 years ago when it would no longer start at 10degrees F without aid.It now needs to be 40 to start with no aid .I pulled the injectors,which pop at 3800psi and have a good 6 hole spray pattern. While the injectors were out I checked the compression,in a 50degree shop,and it ranged from 395 to 440.The charge pressure going into the pump is 16 psi.Can anything in the pump,with only 4100 hours,cause it to start like that ?The service manual does not go into pump symptoms.