Yes. The CP4 just like the CP3 and the VP44 before it, are cooled by fuel flow. Factory transfer pumps flow just enough to keep the pumps right at maximum of that temp curve. Add in the fact that Bosch designed the pumps for European diesel which has more lubricants in it than Us diesel and boom, instant problem. He needs to add an aftermarket lift/transfer pump. It’ll supply the same fuel pressure but larger volume and being how they return excess fuel to the tank, it won’t be a problem. I’d also ever other tank run some LOS in it
a very common problem on all the diesels made since the great p7100 pump was phased out