engine
fuel
system.
comments to me.
This page updated:
November 2008
| Sailboat engine fuel system. |
|
Please send any comments to me. This page updated: November 2008 |
| [My boat] is fitted out with two RACOR primary fuel filters plumbed in parallel, with selection valves. Having them plumbed in parallel means I use one filter at a time. If it gets plugged or water gets in the system I can switch to a different tank and filter without shutting the engine off. These are the filters that have the glass bowls and drains on the bottom so you see what's coming up from your tanks, and sometimes it isn't diesel fuel. |
| Get a Racor filter. You can "see" the water. You can see the color of the fuel (sometimes algae, or worse). You can add a vacuum gauge and you're done -- you'll change the filter when you need to -- not just to do it. It might be two years between changes -- or two months, depending on where you get your tank filled or what you're trying to grow in it. |
|
> What pressure range of fuel vacuum gauge should I buy ?
The standard gauge you will find is 0 to 30". My boat runs at 0 with new filters. I usually change them when they get to 7 or 8 inches. I discovered that it was reading 15" once but the engine was still going strong. If you could find a 0 to 20" it might be a little better but these would be hard to find and I doubt you would see much difference. Racor has their vacuum gauge color-coded Red for Normal 0-10", Caution 7-10" and Danger 10-15". |
| Check with Racor for the correct size of Racor. If the Racor is too big for the flow, it will not have the proper swirl action in the bottom of the unit to coalesce the water. |
|
... arrange things so that there will never be any water
in the tank, easy to do when
making a new tank. Have the tank builder weld a threaded fitting such as a
pipe coupling cut in half, onto the bottom of the tank, say 1 1/2" onto the
bottom at whichever end will be the lowest after installation. Add a
reduction bushing and draw your fuel from there. Even better, add a 1 1/2"
ball valve, then a longer nipple and a bell reducer. The idea is that any
trash and/or water in the tank goes immediately to the outlet where it can be
dealt with and the tank contains only clean, dry, fuel. If there is some
trash in the tank that plugs the fuel feed line it is a simple matter to
close the ball valve and remove the longer nipple to remove the trash. You
could put a strainer unit between the ball valve and the bell reducer to make
it even more tolerant to trash and more convenient to clean. The more effort
you go through to feed your engine clean, water-free fuel, the less often it
will stop running involuntarily. Lack of a plentiful supply of clean fuel is
the cause of diesel engine stoppage about 90% of the time according to
everything I have read. In my own personal experience it has been 100% of
the time.
I use this well setup on Bandersnatch to insure any water in the tank gets drawn out before any fuel comes out and have never had a problem due to water in my fuel. Over the years, as other fuel problems cropped up, I have added more and more refinements to my fuel system to eliminate each problem. Now the fuel goes through a coarse (1/4" holes) strainer in the tank, a fine (bronze window screening) strainer to protect the electric fuel pump (used for priming, fuel transfer, filling filter housing, polishing fuel, testing for leaks and flushing air from the system), a fine mesh screen inside the electric fuel pump, a Racor, and finally the secondary on the engine. Also be aware, diesel fuel does not like zinc. Galvanize your tank on the outside only, or just use plain steel then sandblast and do a good paint job on the outside. I would also recommend you look at heavily built plastic tanks. They don't rust, but there is some controversy about their longevity. Be extremely careful about screwing pipe fittings into plastic tanks, the threaded bosses are prone to cracking and once damaged are very hard to repair. Use Teflon tape and do the final tightening with liquid in the tank, tightening only enough to stop the leaking. |
|
Draw fuel from the absolute lowest point in the tank to minimize the amount
of permanent sludge carried about in the tank. You want the contaminants in
the filters, not in the tank waiting to overwhelm your filters when you have
a MOB situation in heavy weather, drop your sails causing your vessel to
bounce about and stir up the sludge in the fuel tank, and you
really-really-really want your engine to work flawlessly.
A ball valve to shut off the fuel. It would be nice to have valves on *every* opening of the fuel tank, including fill and vent, to seal in the fuel in case of a sinking. It will greatly reduce your problems if the boat is salvageable. An inline screen about the mesh of window screen, easily cleaned. Mine is a Watts brass fitting, obtainable at a plumbing supply. The original screen was much too fine so I made my own from bronze window screen. This screen is just to protect the electric pump and check valve. You really want the sludge to collect in the Racor. Be aware that Racor has filter elements of several different micron ratings. I use the smallest I can get. It is much easier to change one big Racor filter than several smaller secondary filters. A clear section (I use a 2" piece of clear fuel hose with a spring inside it to keep it from collapsing) so you can *see* what is being drawn from the tank like trash or air. An electric impulse type fuel pump (NAPA, Balknap BK.610-1016, red dot, $108) to prime, clean, and troubleshoot the fuel system. This type of pump has a piston and two check valves, just like the old-fashioned well pump, so fuel can be pulled through it [AKA "flow-through"] by the engine fuel pump. A bypass check valve may be required depending on required fuel flow rate when the engine is running. Compound gauges (plus/minus 15psi) on the input and output of the Racor to see the condition of the filter and another between the secondary (engine mounted) filter and the injection pump to see the condition of the secondary. I found some nice ones: Gen Svc Liquid-filled, 304SS case, 1.5" dial, 1/8" ips bottom fitting, PN 38545K42, $23.64 ea, McMaster-Carr, 404 346-7000, credit card, UPS. A crossover valve from the output of the Racor back to the return line to clean your fuel after taking bunkers. Another valve to draw fuel from the system at the output of the Racor if you want to. |
|
> Bought bulbs like the ones on an outboard fuel tank line. > Put them in each fuel line before the primary filter. You are fooling yourself. The squeeze bulb is a band-aid, a baby step. A major problem with the squeeze bulb pump is that minor trash can plug up the small clearances in the check valves. If you put a filter upstream between the tank and the bulb to protect the check valves, the bulb will tend to collapse from the suction of the engine pump and the resistance of the filter, with said collapse increasing as the filter collects more and more debris, squeezing the fuel flow down more and more until the engine quits. ... |
|
I have read that the fuel microorganisms need water in order to live. If
this is true, then if you keep water out of your fuel tanks, you will not
have a microorganism problem. The key to keeping water out of your fuel
tanks is to draw the fuel from the very bottom of the tank. I have wells
about the size of a cup in the bottom of my tanks and my suction pipes go the
bottom of the wells. By doing this I automatically remove any and all water
every time I withdraw fuel from the tank.
Putting the ends of the suction tubes an inch or two above the bottom is a technique left over from the days of professional engineers and day tanks on yachts where the engineer would drain the day tank from a valve on its very bottom to be sure there was no water in it every time he filled it up. Unless you have such a drain valve on your fuel tank, or use the well or similar technique as I do, you *will* accumulate water and associated microorganism glop in your tanks. A fuel preservative would be a good idea for fuel stored for months at a time, but that is only to protect already clean fuel. You really must keep the water from accumulating in the bottom of your tank. |
Fuel tank:
|
| When possible, buy your diesel from automotive pumps rather than fuel docks. The turnover is higher, so the fuel is generally much cleaner and it is well worth the trouble of getting it to your boat. |
| Mount an electric fuel pump as a backup to the manual transfer pump. It makes priming after a filter change easier, and in an emergency will overcome the effect of a small air leak. It also makes it easier to spot air leaks. |
| ... install a vacuum gauge [between primary filter and lift pump] so you can monitor your filter's progressive restriction, avoid unnecessary changes, and most importantly avoid untimely engine shut downs due to a clogged filter. ... |
|
Use the stick method. Pump all the fuel
out of the tank that you can thru the normal pickup. You can use a 12 vdc
pump from Napa and it will do the trick easy. After you have the tank empty,
add fuel a gallon at a time. Either by jug or watch the pump at the dock. and
mark the stick as you add fuel. Please do not do this on a Saturday morning.
The guy behind you will have a fit as it will take a little time.
Then take the stick and transfer the marking to somewhere on the wall in the engine room. If you or the next owner lose the stick the calibration is still available. Now for fuel care. Use that little pump inline with your current system, but leave the pump off. The right pump is one that you can blow thru if it is not powered. Now for the good part. If you have a fuel starvation problem due to whatever, you can turn this pump on and it will draw more fuel thru a clogged filter for a short time. Just what you need sometimes. ... |
|
A leaking or broken injector pipe is fairly common. The pipes are subject to
high pressure and vibration and any flaw is soon revealed. It is rare that the
tubing actually breaks. The usual leakage site is at the joints or
compression fittings, probably due to repeated overtightening. If your injector pipe
leaked two gallons into the bilge it must have been leaking for several hours.
If you discover a leaking pipe during the middle of the passage, DON'T CRIMP THE PIPE SHUT. This will ruin the expensive injector pump. Rather disconnect the end from the injector, slip a plastic tube over it, and direct the open end into a 2-liter soda bottle. Check the bottle every hour and empty it back into the fuel tank. Then limp home on the remaining cylinders. |
|
Re: fuel tank gauge:
Others mentioned the sending units from West Marine. I put one in my tank and the thing I learned is that the manufacturer can't measure tank sizes. They list them as for a certain tank depth, but if you get one, you need one for a tank several inches deeper than what will be listed on the package. I had to take mine back and get the next deeper size, and it still isn't deep enough. I would have gotten the one 2 sizes deeper than the actual tank depth except I had to bend the arm on the second one to get it located before I realized that, even though it was listed as for a tank 3" deeper than mine, it still didn't reach the bottom. Now, when it's about 3/4 full, mine says empty. Bottom line, don't pay any attention to the sizes mentioned on the package, measure the unit yourself and make sure it will drop down as much as you need. |
|
A recirculation polishing system takes advantage of 'turnover' flowrate and a filter that is much coarser than
the prefilters found in a normal "in-line" filter set. A coarse filter will have little resistance to flow (GPM/psid)
and yet have retention ability down to the sub-micron levels ... but not a very high efficiency of capture.
So using a coarse filter with for example a 12v fuel transfer pump (3 gallons per minute @ 1psid)
will allow you to 'turn over' the tank volume many times. Each time through, more and more of the very
small particulates become trapped until you haave essentially a total background of only submicronic particulate.
Coarse filters are cheaper than 'fine' filters. A prime benefit of a high turnover recirculation system is its 'recovery' --- if a
huge amount of particulate comes loose from the tank walls, the particle load will 'recover' back to normal due
to the high turnover rate --- With a lift pump (at about 2 gallons per HOUR capacity in comparison to a transfer pump
at 3 gallons per MINUTE (180 gallons per HOUR) ... the transfer pumps system will turn-over almost
100 times as much fuel in the same time!
I'd disagree with the use of a Racor; they are relatively expensive (huge mark-up for the distributor/reseller) and are more or less designed for 'single pass' filtration. For the filter I'd recommmend a 2.5" diameter by 10 inch long, spun bonded polypropylene microfiber media 15-20 µM about $8 in a cheapo carbon steel 'oil-burner' filter ($60). Since such transfer pumps usually come with a protective suction screen, I'd pressure-feed the filter with the transfer pump for the longest in-service life of that filter (vacuum-feed filters are VERY inefficient with respect to 'on-stream or 'service life'). A Walbro model 6802 12v 3 gpm transfer pump is about $150. |
|
Re: Epoxy tank coating:
Go very slowly in building Epoxy tanks intended for gasoline. The formulations of fuels have been changing. What you build for gas in a few years may have other additives in it. By law and in pursuit of profit, fuel is expected to contain more and more Ethanol and other alcohols in the future. Some are destructive of Epoxy. I understand there have been more and more problems of late with tanks failing due to other solvents in the gasoline. ... We earlier talked to the West system epoxy experts and they advised of the problems with some gas formulations ... |
|
Article by Durkee Richards in July/August 2005 issue of Good Old Boat magazine Fuels:
Advantages of bio-diesel and bio-/petro-diesel blends:
Disadvantages of bio-diesel:
From Nigel Calder in 2/2008 issue of Sail magazine:
From page on Sail World:
|
|
Re: Can gasoline be used in a diesel engine ?
Gasoline and diesel fuel are very similar. Gasoline is the portion of crude oil that boils between about 100 and 400 degrees F. Diesel fuel is the portion of crude oil that boils between about 400 and 600 degrees F. However, an ordinary diesel engine will not run on gasoline, and a gasoline engine will not run on diesel fuel. A gasoline engine works by compressing a mixture of gasoline vapors and air in a cylinder and igniting it with a spark, driving the piston and creating the power. A diesel engine works by compressing air in a cylinder and injecting a liquid fuel into the cylinder. The air must be compressed to a high enough pressure (much higher than a gasoline engine's pressure) that it will be hot enough to ignite the fuel without a spark. If you try to run a gasoline engine on diesel fuel, the fuel will not be vaporized satisfactorily, and if it ran at all it would be sluggish and would exhaust a cloud of smoke. If you try to run a diesel engine on gasoline, the gasoline will vaporize and ignite prematurely and the engine will sputter and knock and eventually stall. (I know this from experience because I once rented a car that I did not know had a diesel engine and I filled the tank with gasoline.) Kerosene and jet fuel are portions of crude oil that are similar to diesel except that they usually will not contain the highest boiling part. They should work in a diesel engine, but not in a gasoline engine. |
| Home | |
| Site Map |