5.9 QSB warm start issue

Hey guys running into an issue with one of my engines. It starts and runs perfectly every time from “cold” start. If I leave the block heaters on to where it keeps the oil temp around 130 the engine will not start. It’s as if it’s completely dead, no crank or turnover. This just started this week, happened while out fishing. So I left block heater on for a few days, came back wouldn’t start. Turned them off for a day and came back, started right up.

Same thing would happen if I run the boat and shut the engines off. Port engine won’t start, but could be jumped. To me it sounds like it could be the injector pump, wanted to get some feedback. My Cummins mechanic is booked full for the next 3 weeks so won’t be available until after I winterize it. trying to see if it’s anything else to look at so I can use it before the boat gets put away for the winter.