My goodness, don't risk taking your Super Duty to a "Diesel Shop" - this engine has Ford specific diagnostic equipment required and Ford technician training that is really beneficial. I can't say it enough that a true trained Ford Diesel technician is such a value when you have a truck like this.
Guessing like they are doing is only costing you money and making it more complicated with replacement parts (likely unnecessary).
"Power issues out of the PCM"? I hate to say this, but a PCM merely "grounds" a circuit. It does not power anything.
I'm quite concerned about the service you're getting at the chosen shop. Seek proven Ford Diesel tech help near you -- at a reputable shop or at the local Ford dealership.
www.repairpal.com/repair-shops
A bit late for me to find this post, as I had a similar issue with my 2016 F350 Diesel 4x4 with 95K miles. Ran perfectly and parked it in the garage for about two weeks and decided I needed to put some miles on it, heat up the engine, and get it up to operating temperature. Never had one starting problem... until last week.
I looked at Forums and the input made by some was so unrealistic, I thought it was about... anything. Turned over the engine and it turned over fast and after a couple seconds, I figured it was not going to start. It usually starts once the engine turns over. Had my wife looking under the hood with a flashlight and the engine was turning over.
After a couple days of browsing the Internet and people spending $1,000's for various fixes... I was really depressed about my well kept F350. I do my own oil, air and fuel filter changes. So... WTF... I felt totally... screwed. But from what?
Since I do my own Service... I have had NO Water to drain. I removed the filter cover and the filter was OK. The Diesel Fuel had no water in the bottom drain and was nice a fresh Diesel Amber. I removed the Filter Cover and Filter and puled the RUBBER GASKET ON TOP OUT.
I reinstalled a New Filter and Gasket. When pushing the rubber round gasket UP over the Threaded Section I passed what is the position of where the Rubber Ring...should be. Seeing that below, just above the Threaded section was where the Round Rubber Gasket should be placed and I moved the gasket DOWN to where it should have been. Had my Wife turn the Ingnition ON... it turned over... and STARTED as it always does. Holy Crap... the only thing I can think of is I had the rubber gasket TOO HIGH and above where it belonged on the last filter change.
Being a bit Paranoid... we both started the F350 and when up the uphill asphalt road in the event the engine quit, or... etc.. It ran as it always did. Drove it a bit further... just perfect. The Turbo kicked in on the Highway as my next test... a Rocket.
I BELIEVE THAT THE LAST RUBBER RING GASKET WAS ABOVE THE GROOVE. WHERE IT SHOULD HAVE BEEN. I had a flashlight to light the area... and discovered my error. I suspect it was the previous round rubber fuel filter cover gasket let AIR into the system parked for a long period. I removed the previous gasket and did not note it was too high, or not. I installed the replacement doing the SAME TOO HIGH POSITION and saw I was ABOVE THE GROOVE ABOVE THE THREADS. The rubber ring gasket was set where it should be... installed the Fuel Filter mounted into the Casing...had my Wife turn the ignition to ON, so the electric fuel system could do... something... and said CRANK IT.
IT STARTED IMMEDIATELY... and RUNNING PERFECTLY FOR SEVERAL SHORT LOCAL TRIPS... not being 100% SURE if that fixed it. RUNNING LIKE IT USE TO. STARTS IN A SECOND OR TWO..., and Turbo Kicks in and Off we Went.
Avoid all the crazy nonsense costing $1,000's. We are both elated. Runs perfectly as it always had. REPLACE THE FILTER AND PLACE THAT ROUND BLACK RUBBER GASKET WHERE IT DROPS IN ABOVE THE THREADS. We are both 'shocked' it was an easy fix... by accidentally changing the filter ands rubber gasket. WENT from Depression to Elated after several days try to find a fix on the Internet. Some advice not to be taken seriously. This worked. Try it... the worse that could happen...you now have a clean Diesel Fuel Filter. We were both...happy, happy, happy. The fix was simple and did not expect anything... but it worked.
Thanks for reading this to the end. Sometimes go to the most simple FIX...which is a fresh Filter and placing the Rubber Gasket where it drops int the right spot.