There is actually an explanation. Orks are bound together by something called WAAAAGH!!! energy. Essentially, if enough Orks believe something will work, then it will work. For example; because they believe that their vehicles go faster if painted red, then red vehicles go faster. They will also move with no fuel if they believe there is fuel in it. The Imperium did experiments were they couldn't fire Ork guns but then handed them to Orks and suddenly the guns worked perfectly. Then the guns stopped working again once they took them back from the Orks. It does come with the massive weakness however that if there aren't enough Orks near their technology, then it will stop working.



Does that answer your question?