Originally Posted by Jeff753
I drained some fuel from my water separator and found darkish fuel with small black flakes. I was going to put some biobor jf in it but thought I better wait until I get closer to home in case I go through multiple filter changes.
Ideas or comments?
On a related note Arnold (Cummins Ocala) who is one of their best mechanics told me to plug the center hole on the primary and prefill it with clean fuel. He told me to put the secondary on dry and use the lift pump (3-5 30 second cycles to fill the secondary. Seems most people fill the secondary too??
Yup.. Water.... and old fuel.
Diesel fuel starts to break down within 60-90 days of refining. That is the darkish color. It actually coats the inside of your tank with tar.
The black flakes are likely microbes growing in the fuel at the water/ diesel fuel interface.
There has been much discussion and misunderstanding of algae in diesel fuel. Algae need light to live and grow. As there is no sunlight in a closed fuel tank, no algae can survive, but some microbes can survive and feed on the diesel fuel.
These microbes form a colony that lives at the interface of fuel and water. They grow quite fast in warmer temperatures. They can even grow in cold weather when fuel tank heaters are installed. Parts of the colony can break off and clog the fuel lines and fuel filters.
Water is heavier than diesel fuel so the fuel rides on top. Stuff lives where the water meets the fuel. No water no microbes.... The microbes can actually get quite thick. In a boat in rough water the fuel can get stirred up and the microbes distributed in the fuel and end up in the filter. Unlikely in a MH.
I could be wrong but it might be an indication that if it is indeed water in your tank, that it is getting a bit deep and close to the fuel pickup and the microbes are getting pickedup. ( not good ) I base this on the assumption that you are not off roading at 50 miles per hour in your RV so the fuel is not going to get shaken up much.
Water usually enters the tank via bad diesel fuel or via condensation through the fuel vent. Not much you can do about that one. Always get your fuel at a place that goes through a lot of fuel. Like truck stop. Some local garage that goes through a tank every 2 months is a poor choice.
My advice is to dump the fuel, and send it through a water filter like this link.
This actually works. All the fuel that goes in to my boat goes through Mr Funnel. Filters out the water. Cheaper and faster than using up fuel filters.
Then mix it with some fresh fuel and use it quickly. You should always add a biocide to your fuel and if the MH was built prior to the low sulfur fuel coming in around 2003 you should also be using some additives for lubricity. The sulfur in diesel fuel was used to lubricate the hi pressure pump and the injectors, much the way lead lubricated the valves in gas engines. No sulfur now so you need to add lubrication.
Manufactures even recommend the additives for new engines because its simply too dry and the pumps don't like it.
My blue water sail boat has a 75 hp diesel that cost me 20k to replace a few years ago. I always add biocide and lubricity additives.
I also have 2 -30 micron filters that the fuel goes through and then 2 10-micron filters. They are actually set up so that it goes through one 30m filter and then through a 10m. Any problems and I immediately flip a couple of valves and we go to the second 30m filter and the second 10m filter.
There is nothing like going in through a narrow cut in 6 or 8 foot waves and a 25 or 30knot breeze and loosing your engine. The natives will heartily disapprove.