A short example here so as not to occupy too much writing space. When I was studying Automotive Engineering in the late 80s' I came across a rotary engine vehicle which had been abandoned by the owner because the engine could not start. The owner had sent it to various places but no one had fixed it so he gave up on it, as getting another engine from Japan was like half the price of the car. Anyway he let me have a look at it, I went through the entire vehicle for a few days. Short of opening the engine and I'd never opened a rotary engine before, I ran compression tests and ignition timing tests too. All seemed fine, the firing order was okay too. I found another scrap engine with someone else and opened it up completely to understand what was happening inside. Now a rotary engine does not use camshafts nor valves so it was a new experience. After a few days of looking into the engine design, I realised that the fuel needed by the engine was unleaded. Back then in Kenya, there was only leaded fuel. This was the problem. The exhaust gases contained carbon deposits that were going into the catalytic convertor thus choking the exhaust system. I took a hammer and a chisel and pierced a large hole into the cat convertor. The engine started with one kick! We replaced the cat convertor with a standard silencer. However I told the owner that if he liked the car so much, he must import engine parts because the leaded fuel would wear down the compression rotor seals very quickly. Eventually I did get the scrap engine started by using materials from exhaust valve stems that run high temperatures. There are many times even these days I get some friends who call because their cars have problems that are not easy.