Bad diesel fuel

Gooding. R wrote:
Also remember, some diesel machines have 2 fuel filters. A primary(small) and a secondary(large) filter. You can change the big filter till the cows come home and still have a clogged filter. The small filter usually has a scraper handle on top, but this is only good for several uses and you have to change the filter.

I had a friend who had problems nearly identical to the OPs. It turned out that his particular rig had three fuel filters. The first half dozen shops he took it to had no idea. He replaced filter after filter, had many of the fuel lines replaced, had the tank dropped and cleaned, spent a small fortune and the problem still did not go away. The last shop had one mechanic who knew that there was another filter. It looked like it hadn't been changed since the coach was new and it was clogged nearly solid. His engine has been purring like a kitten ever since.