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Old 04-28-2014, 06:29 AM   #1
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Join Date: Oct 2007
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Fuel system cleaning

This discussion was lifted from the Flxible bus board , but fuel problems are fuel problems , bus boat or truck.

Some good observations from long years at the battle.


MUCH too much complication on a very simple but important subject.

As to how to change filters and keep from running out of fuel, easy. tmmr had the right answer. Remove the fuel filters from their screw mount (if you STILL have insert cartridges from the last century PLEASE break down and go to Detroit Diesel and get a swap over kit to a spin on cartridge. New Detroit Diesel Spin on Oil and Fuel Filter Conversion Kit | eBay Your life will be so much easier)
Once the old filters are off inspect the filter screw base for a square o'Ring (quad ring) seated at the underside of the filter housing on the spin on lug. Remove it and replace it with a new one in the filter kit. If you fail to tdo this and the ring is old are damaged, the engine will draw air and will either stall or not start at all.

Fill the new filters to the TOP of the element. If you are a obsessive compulsive personality (as I am) place your thumb INTO the large center hole of the filter and pour the fuel into the radially spaced hole or slots around the filter base. what this does is INSURES that NO dirty fuel makes its way into the sensitive injectors by pouring contaminate fuel into the clean or filtered side of the filter. One at a time move the filters to the base of the mount housing and screw them on until the gasket CONTACTS the filter housing, then turn the filter 3/4 of a turn by hand and the job is complete. Some people insist on seating the filter using the filter removal wrench to 'insure' a good tight fit. Wrong approach. If the filter is installed TOO tight it CAN deform the fuel filter base and cause an air leak and when you go to take it off you will find yourself arguing with a filter that REFUSES to be turned in reverse. Need a GOOD all around filter wrench? One that will fit ALL fuel and ALL oil filters and one that NO ONE will fall in love with and will be THERE where you left it, even if THERE is on the side of the road almost on the yellow line? Try this Napa 77 3149 Nylon Strap Oil Filter Wrench | eBay $6 at NAPA.

Once both filters are installed and snugged down you may start the engine. Once started, hold the throttle at 12-1500 rpm. This is a precaution against any air having gotten into the fuel system while the filters were off. After 2 minutes of sustained operation the job is done.

The Detroit Diesel 2 stroke engine as offered by Detroit has many different filter mounts as an option and even has NO filter mount as an option. (housing delete). If it is the latter, they offer a recommendation for filtration when the OEM puts the engine into the truck/bus/equipment. The specification are this, there MUST be a filtration devise in the fuel supply that eliminates all liquid water and solids down to 2 microns. THAT is the specification. In practiced it is not that simple. Historically, diesel fuel has had an atrocious history of contamination. The primary causes are handling and storage shortcomings. Back in the day diesel fuel was transported to remote markets (markets that had no reasonable access to refineries) via barge, train, or truck. Each container was reused over and over again without being maintained or cleaned. Point of sale operations had storage tanks in the ground (5-9k gallon) and would turn inventory over maybe every 2-3 weeks in out of the way places. Any number of contaminants would collect in these tanks but water was the dominant contaminant. This was due to the fact that the storage tank, when down to half full, would expose a large surface are of their steel tank to the ambient air that was free to circulate in the take. The moisture laden water would condense on the exposed sides of the steel tank (kept at a constant temperature by the ground) and the condensed water would coalesce into larger droplets and sink to the bottom of the tank, there to lay until pumped out but the service pump.

No acceptable means of removing this water was available other than to pump it and this cost money. Once the water sank to the bottom, anther situation occurred, the growth of algae. This phenomenon took place at the junction of the water and diesel fuel and further contaminated the diesel every time a new load of fuel was introduced into the tank. Once into the main body of the fuel supply it was pumped in the customers tanks. Once the fuel system is contaminated the contamination spreads to each and every nook and cranny of the duel supply system. Since the diesel fuel system of MOST equipment is designed to 'circulate' the fuel from the tank to the injection pump and back to the tank, perpetual contamination is the lot of the diesel engine operator.

It was in this environment that the dual needs of the manufacturer and the equipment operator came to the surface. The engine manufacturer demanded 10 micron filtration but the filter could not function effectively i the rough and tumble world of bulk fuel handling so, another filter was added to the sister. It has been variously referred to as a nut and bolt filter because its micron rating of 20-25 micron. Why the two ratings, simple, the fuel flows FIRST throughout the 25 micron element and removed all large contaminations that can prematurely PLUG the 2 micron filter if it were left unguarded. The FIRST filter to receive the fuel is called the PRIMARY fuel filter. Once through this filter it is on to the SECONDARY filter for final filtration down to the 2 micron level.

Now to know WHY there are two filters and what they do and how they do it. Now, on to the capitalist approach to fuel filtration.

Remember the above problem of contaminated fuel with water and algae? If a system gets contaminated with algae a complete system tear down and flushing is in order. No other approach is suitable because of the ability of the biological ager to reproduce itself in the system. If a system is left to sit (think the Sexy Flxy in BC Columbia-she NEVER gets out of her back 40) for any length of time, serious damage can befall the system. Because of this phenomenon, MANY schemes have been devised to break this cycle.

The MOST effective approach is to clean up the distribution system. The handling of fuels, the containers they are stored in, the construction and maintenance of the storage devises have ALL been improved in the 70 years since this problem was defined. I drove an 86 Oldsmobile for 50,000 miles-it had 80,000 on it when I purchased it) and when I dropped the fuel tank on it, it was pristine…to a fault. But, I had use, almost exclusively, premium diesel in the tank. Premium diesel is handled in a very deliberate way, being filtered before it is dispensed into the tank. But contamination can occur in spite of careful handling and there is quite a market to address this possible contamination of fuel.

As a point of information, in all of my dealings in the on road and military operations of large equipment (and I DO mean BIG equipment-I operated one of these for the Army in Texas, Korea, and Viet Nam) M88 Recovery Vehicle - Wikipedia, the free encyclopedia
the Primary/Secondary fuel filter system was sufficient for the efficient and effective job at hand. If ever a fuel distribution system was overwhelmed with extremely contaminated fuel, the system itself had to be dealt with, NOT the Pri/Sec design of the fuel system.
I tell you this because there are MANY systems and methodologies on the market to 'solve' problems that don't need solving. What needs solving is keeping the fuel clean before it gets into your tank. But here are some of them.

The fuelwater separator. I put this at the top of the list because it is both a blessing and a curse. If you keep your fuel tanks cleaned (drained of water) regularly the fuel water separator will have NOTHING to do. Here is a fact-the primary AND secondary fuel filters previously mentioned BOTH have treated media (media is that material that actually filters the fuel) that causes the surface tension of the water to be trapped by the filter. IF you find that your primary filter is clogging up it is almost a given that the culprit is water being trapped on the outside of the filter media. I WANT TO KNOW THIS AHEAD OF TIME and the clogged fuel filter is an early warning devise for this.

However, there ARE auxiliary devises out there on the market that claim to be able to remove the water prior to entering a filter (there is often a primary fuel filter associated with this design) and this trapping of the water creates a settling reservoir that will trap the water and solids in a bowl. The road show demonstration even shows cigarette ash being scattered into the unfiltered sample and being trapped by any number bells, whistles, gongs, and plates. The process is simple, it causes the fuel velocity entering the devise to be slowed down and sent into a settling plate that causes the water molecules to be attracted to each other and when they come into contact with each other, they fuse and grow larger, dropping down to the bottom of the collation bowl to be drained when the level of the water gets to a certain point. They work EXACTLY as I have described them and YET I have had MORE road breakdowns using these type of separators that any other single piece of maintenance equipment. The radon is simple, the devises are complex in design and complicated in construction. There are 6 individual places on the devises that can…and DO, leak air. SInce the devise is ALWAYS mounted on the suction side of the fuel system, you can NEVER know where the devise is leaking air. Air leaked into the system will shut you down faster than hitting an Interstate bridge overpass. See here,

There is ANOTHER variation on this devise that is often incorporated into the fuel water separator, a fuel heater. It is generally known that a heater on a fuel filter is a needed option in certain climates but there is a design disconnect with the heater element use on these devises. Remember, diesel fuel is CONSTANTLY being recirculated from the engine to the fuel tank. The tanks are exposed to the passing cold air and the fuel is kept in a cold condition when traveling down the road. The fuel WILL pick up engine heat as it passes thorough the injector pump but the transfer value is small. For maintenance purposes these heater separators are almost ALWAY located out side of the body or on a frame rail with ambient air passing throughout he compartment. The problem with the devises is this, their heater mechanism is ALWAYS too small to maintain fuel temperature across the filter element (the design concept is to have the fuel temp raised up to at least 40° F so that the paraffin in the fuel will not congeal and clog the 25 micron filter.) As such the devise becomes unreliable and fuel gelling will cause the vehicle to shut off. This would of itself not be too bad but when it happens on the road, often times the repair process to get at the clogged filter will leave the devise improperly services and it will draw air again and you will be stranded down the road again…often in as little as q mile or so. Again, I cannot tell you the number of times I have had to chase a fuel freeze up repair more than once because the mechanic wanted to get back home to the warm fireplace.

Another gadget is called the Fuel Slicker System. It is sold under various names but in essence it is a fuel recirculation system that constantly pumps fuel from the tank to a dual fuel filtration system (can you say primary and secondary filters) when the fuel is pre filtered and returned to the tank for normal use. The idea behind the system is to cleanse the fuel of ANY contamination (including algae) by forever moving the fuel through filtration. This process goes on as long as the vehicle key is on. It was designed to answer the problem of algae contamination in the on board tanks. It worlds by constantly cleaning the system of ANY contaminants. The PROBLEM is this, it NEVER removes the offending contaminant completely. Its' operation merely keeps the algae contamination level to a non critical level that would impinge engine operation. For $750 plus installation and a few $200 road calls for dead batteries because the driver wanted to listen to his tape deck, I would just as soon drop the tanks and have them cleaned out.

These are the MAIN categories of fuel filtration. There are many more sub categories too numerous to mention.

How does one navigate through all of this stuff? If you listen to those who have a product to push you will spend more time at the parts store and the garage putting stuff on and fixing problems and then taking stuff off again. What can you do?

I will tell you more in another post. I'll call it the Fuel Dilemma for the Diesel Operator.


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Old 04-28-2014, 01:59 PM   #2
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Interesting in a sort of historical way. But since there is no light in a diesel fuel tank and algae are technically plants that need light to live, there is no algae growing in the diesel fuel. Bacteria perhaps but no algae.

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Old 05-01-2014, 05:30 AM   #3
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What lives on the water interface with the diesel is delighted to eat the diesel as its food.

The bodies and waste stick to the tank sidewalls and come loose with fuel tank agitation. Bumpy water.

What ever you choose to call them , they make poor pets , and clean tanks make for more enjoyable boating.
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