Spent some time with a field tech looking over a sprayer, FPT engine - 6 cyl - 6.7L - Common Rail
Machine was at roughly 80hr when the issue began occurring, main complaint slow/hard starting.
Tech had went the way of a fuel system problem, replaced the HP pump as it also contains the lift pump and replaced the main filter housing as it contains a check valve to prevent fuel drain back to the tank.
The first thing we checked was the fuel supply, scoped the metering valve PWM, rail PSI sensor output and CMP/CKP correlation, did a 3 start/stop test, all checked out good.
Our findings were the fuel system is spot on as is the CMP/CKP correlation, the starter current was odd on the problem machine and after getting the known good for comparison I knew we were onto the source of the problem.
After having a chat with the tech & service manager we determined the likely source of the higher than normal load on the engine was the unloader valve (malfunctioning) for the main hyd pump.
The valve coil is commanded on (unloading) during startup, once the ignition is released to the run position, the coil de-energizes putting the pump into a full load state.
The tech tested the coil for short and open, all was good, ran a independent 12volt feed to the coil and the engine cranked and started in <4 sec. where before it was upward of 10 sec.
There was no concern for the ground side of the coil wiring as its a shared ground and the machine had no other issues. The hyd control is a Parker iQAN system, it was determined that somewhere in harness from the iQAN node to the coil it suffered a broken wire.