If the fuel is draining back he should have air at start up. No air would indicate it's not draining back. So something is causing it to take 5 seconds to build pressure, maybe a bad LP
Had a job awhile back that I could have used this boring bar on. So now that I don't need it I have it setup. Lol
also got more tool holders and a storage cabinetand here I have a couple more boring bars I might get set up
Need to go back to basics. Verify fuel pressure at IP . Verify glow plugs are working properly. Etc hopefully your engine is ok if it shut down from loss of oil pressure then chances are the bearings got toasted.
Afaik there is no such thing. I wouldn't bother with the relearn until you get it running right. If you haven't touched the IP it shouldn't have changed.