Rhumb Lines June 2017 Issue

Dealing with Bad Diesel

About this time of year, many of our readers will experience a gradual loss of engine power, maybe even a complete shut down. They’ll pull the filters and find them so clogged you’d think the last fill-up was a spinach smoothie.

Filter Boss
A twin-filter fuel polishing system like the Filter Boss (left) supplements other fuel management practices to prevent contamination.

The bad news is that getting rid of that gunk will require a bit of an investment—if not in money, then time. The good news is with careful fuel management you can prevent this from happening again. If you have persistent fuel issues—gasoline or diesel—be sure to read the series of fuel-related articles found in our online archives. Just search “fuel tank” on our website.

Here’s quick look at your options for resolving a contaminated tank as laid out by systems guru Steve D’Antonio in a past issue of Practical Sailor:

For even a mildly contaminated fuel tank, you need to gain access to its inside. Organic contaminants include biological life forms both living and dead and mineral-based debris includes asphaltine, a tar-like, mineral-based substance that accumulates before it ever reaches your boat’s fuel tank. Additives may help prevent some contaminant build-up, however, no additive will remove years of accumulated organic- or mineral-based sediment or water—no matter what they claim. As for those miracle magnets that have reappeared on the market, we’ve seen no science to back up claims that magnets, or a “specialized light source” will stave off fuel contamination any better than common protective measures including filtration and regular treatment.

As several of our tests have demonstrated, it is possible to limit contamination (and tank corrosion) with the use of additives. A biocide like Biobor JF can help to control or limit biological growth, and as we found in our testing, this can be supplemented with an additive like Startron to fight corrosion. (See “Diesel Additives,” PS August 2013, and “Diesel Biocides Take on Contaminated Boat Fuel,” PS July 2009.)

Keep in mind that every time you shock or treat the tank, the bodies of what you kill will accumulate in the tank. No additive will dissolve their skeletons, which are abrasive and harmful to your engine’s fuel system. And too much of a good thing can be harmful: Some biocides, if overused, can be corrosive and damage your metallic tank or other fuel system components.

The best way to stem biological growth is to keep water out of the tank with a good tank design that allows access for cleaning and facilitates elimination of water (see “Diesel Fuel Tank Replacement,” May 2007).

If you want to be certain that your tank is clean, the best and only sure way to do it is to get inside the tank. It’s not as difficult as it sounds: Access plate kits are available. One, manufactured by Sea Built Inc., www.seabuilt.com, comes in several sizes; these can be installed on the tank top or side by a skilled do-it-yourselfer or your favorite boatyard. Once the inside is accessible, cleanup can vary from light duty swabbing with a lint-free rag (never use “shedding” paper-based products), to the heavy-duty, requiring mechanical abrasion with paint scrapers, gasket removers, brushes, and solvent. (Note: Access plates won’t work with plastic tanks.)

How often you’ll have to do this chore depends on the quality of fuel you take aboard. Poor-quality fuel will increase the frequency of this event, while careful fuel dock discretion or funnel filtering may mean you’ll only be seeing the inside of your tank every four years—a familiar interval for dealing with built up detritus and debris in the U.S.

Comments (5)

The preceding comment mentions ethanol, this was mentioned by Peter Kerrin, Diesel Pure Inc. in our conversations on solving microbial fuel issues. Peter had mentioned that ethanol was now finding it's way into the diesel fuel stream and by virtue of it's affinity for water, enhances fuel degradation. He also cautioned that the fuel treatments available today have not necessarily been re-engineered to deal with the presence of ethanol and may in fact work adversely due to it's presence. So, as recommended, avoid it if you can or/ and check the stabilizers that you do use specifically include suitability for use in bio-diesel fuels.
With the growing mandate for ethanol blending in North American fuel streams it's probably safer to assume there is ethanol present and act accordingly.

Posted by: GM Ross | June 15, 2017 9:19 AM    Report this comment

My 2 cents:
- No such thing as too much filtration
- Switch to a transparent-bowl...also put in an inline pump/bulb, and an inline vacuum gauge (with tracer needle) as this will give you advance warning of and help diagnose all kinds of potentially bad things that might be going on.
- Stay away from biodiesel and if you have to use ethanol go for the lowest %
- Keep fuel tanks full (less air surface area expose for water to absorb into and promote bacteria growth).
- Install a H2Out water vapor absorber in the fuel tank vent line
- Replace degraded Fuel cap O rings

Posted by: CA Dude | June 14, 2017 1:50 PM    Report this comment

My experience with microbial contamination has led to discovering much of what's laid out here. I began with the addition of two additional tank top access covers to get in to all three chambers of the tank - 2 baffles built into the tank necessitated this. My boat had been laid up for 4 years, with indoor storage I presume warm summer temperatures over that interval had promoted quite an in-tank bloom.
The tank was not exceptionally dirty, more so the presence of water was promoting the biological activity. I had the good fortune to meet a fuel solutions fellow from Halifax, Nova Scotia - Diesel Pure Inc.
Practical Sailor doesn't permit external image links, HTML, etc so I'll describe what I've built. It's a three stage arrangement consisting of a primary crap trap, a 1st stage water type filter followed by 10 micron 2nd stage and 2 micron 3rd stage Racor filters in series. A Vacuum gage provides visual indication of filter status.
To accommodate this polishing setup I added a set of inlet/ outlet drop tubes that extend to the low corner of the tank, in the same vicinity of the existing fuel pickup feeding the engine/ filter/ pump. The pump that I've included in this setup (approx. 6 psi) is to be powered from a timer/ solenoid that will run the pump for an hour each day or, on a manual over-ride any time new fuel is taken on.
Since the main fuel pickup draws from that low corner of the tank it's guaranteed to draw from any pool of water naturally collected there. By drawing from and returning the polished fuel into that same zone I anticipate I'll create sufficient turbulence to agitate and capture the water. As I understand it, the microbial action takes place in the interface zone between fuel and underlying water. Eliminate the water and the microbial activity ceases.

Posted by: GM Ross | June 14, 2017 2:55 AM    Report this comment

Jackie and I were arguing about whether the waves crashing against the nearby lee shore were splashing 40 feet into the air or only 25. We were chugging along the southeast coast of Grenada toward St. David's where we planned to lay up CHILL for the summer after our second season of cruising in the Caribbean. We had spent three days at La Phare Bleu Marina vacuum bagging our clothing and linens, stripping all the sails and canvas, stowing and securely chaining our outboard in the lazarette, and blocking and strapping the dinghy on deck. All was set to haul, we had only to power 5 miles into what turned out to be a 35 knot easterly to reach Grenada Marine.

Our argument was cut short when the diesel faltered and died. Ducking below I found the vacuum gage on our Racor reading about 25psi, a situation fortunately relieved by switching to the starboard tank. With more leisure to investigate later we found the filter element clean, but the 5/16 metal pickup tube completely stopped with about twelve inches of stringy black sticky stuff from the tank. Thus my interest in the subject of this article!

The only access to each of our plastic diesel tanks was through the 1.5 inch holes for the pickup tube and the fuel gage sending unit. I built a polishing system from a spare fuel pump and a used Racor that I bought from a machine shop. The only problem - the old Racor used spin-on filters that cost about $25 each. We didn't want to burn through a stack of these while we vacuum-cleaned the bottom of our tanks. So Jackie built a conical vacuum attachment for the polishing unit inlet hose and secured some kind of fabric to the inside of the cone. She used a straightened coat hanger to guide the vacuum here and there all around the bottom of the tank, pausing periodically to remove it and clean or replace the fabric.

Messy? Yes. Effective? Yes. Something a cruiser can DIY in the middle of East Nowhere? Yes. Extremely helpful to have a can-do wife with a creative attitude who is not afraid to get her hands dirty? Yes, yes, yes!

Posted by: Annapolis Sailor | June 13, 2017 3:05 PM    Report this comment

I checked out the Fuelright site and found the product claims and test results to be impressive,however the testing is inhouse;I'd prefer to see some independent lab tests before using or recommending the product.

Posted by: Capt. Singood | June 11, 2017 2:19 PM    Report this comment

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