cleaning diesel tank

Good question. I can see pumping the fuel out, but how does he get into the tank and clean it???

It is called "fuel polishing" and is very common on diesel powered boats.

Basically, they have a large capacity pump and filters. They suck off the bottom of your tank and return it through the fuel filler. When their filter no longer show evidence of contamination, you are done. Typically, they will filter each ounce of fuel in your tank a couple of times, and the high flow rate is pretty effective at getting any "gunk" in the bottom of the tank stirred up and filtered out.

If possible, I would look in there and see if it needs it. You can buy a camera for this purpose for as little as $30 that simply plugs into a USB port.
Could be like furnace duct cleaning where the ducts are often already clean.

How do you know the tank is dirty? Miss in the motor? Am I missing something here? If it is not broken you don't need to fix it,right? Tom

I wouldn't clean my fuel tank unless it was so full of crud that fuel filters are getting blocked.

As usual Brett is dead on. Algae and sludge will build up in your tank especially where you have large temp. swings. A good fuel treatment/algaecide will help but the filters do the main job of keeping it out of the injector pump. On our coach we have 2 filters, a primary with the transparent bowl and the secondary which is the finer mesh. When I start seeing the black sludge in the bottom of the bowl the top of the filter is getting toward the blocked off stage. It's hard to see in performance of your coach since the blocking is gradual but when you change filters it's like having a hot rod. There's a place here, Clean Fuels Inc.(they have a website w/locations) that is a branch of national chain. They have trucks that will come to you and do the service or you can go to them, preferably when there's not a lot of fuel in the tank as they charge by volume. When clean go fill the tank and add the required amount of algaecide treatment.

Hope this helps.

Dave