Norm's Fuel System Description

I have had some requests for information about my fuel system and apparently my previous descriptions cannot be found in the archives. So I cobbled up a reply from several old messages - took about four hours. Hope it may be helpful.

Since I built my boat from scratch, I have had the opportunity to create and modify my fuel system at will. Whenever I had some problem, I changed the system to eliminate that problem. Eventually all the problems were gone. Here is what the result is.

First step, and the hardest to retrofit, is to have your fuel tanks built with a well or pocket at the very lowest part of tank. Imagine a 1 1/2" threaded flange welded onto the bottom of the tank at the lowest corner. Then imagine a stainless nipple threaded into that followed by a bell reducer down to your fuel line size. Add a tee to that with a drain valve on the bottom (if accessible) and the suction line out the side of the tee.

The well in the tank insures that everything that sinks to the bottom of the tank gets removed at first opportunity and there is never any water or trash in the tank during operation of the engine. If you can't do a well on the bottom of the tank, then perhaps you can arrange to have your normal fuel suction tube suck from the very bottom of the tank. It might be feasible to add a short section of fuel hose to the pick-up tube to suck at the spot anything sinking (water/sludge) will migrate to.

The entire concept is to withdraw any and all water or sludge that settles to the bottom of the tank in the normal course of vessel operations. Any water or sludge that finds a permanent home in your tank will rise up and try to kill you some day. What usually happens is the weather makes up and stirs the glop in the bottom of the tank enough to overwhelm the filters and stop the engine.

Then you have to take corrective action under the worst conditions with an fuel system, while adequate for most conditions, is now inadequate for the conditions you find yourself in. We all have heard of the results of this, sometimes with mention of salvage or photos of the wreck. Have ball valves (I like Apollo brand, West sells them), on each suction line, return line and vent line of each fuel tank. The vent line valve is to seal the fuel in the tank in the event of a sinking. You can remove the handles if you are afraid someone will close them inappropriately.

Oil spills are frowned upon, especially in harbors, and having a way to easily close up the tank entirely, say when a hurricane is approaching, can save a lot of extra grief in an already bad situation.

After the fuel tank suction valve(s), I have a short section of transparent fuel line, with a spring inside it to keep it from collapsing under suction with hot fuel softening it. Although it has turned quite dark over the years, it was helpful early on when I was getting air in the suction line due to a cracked fitting inside a tank. Perhaps the glass sight glasses used in Freon lines would not turn dark.

After the clear section there is a bronze strainer (Watts makes the one I have), to protect the pump and bypass check-valve. It came with a rather fine screen that plugged easily so i replaced it with a screen i made by soldering together a cylinder of hardware store bronze window screening.

Then the electric impulse-type fuel pump (a NAPA Balkamp BK.610-1016 about $120) with the bypass check valve across it. the check-valve bypass is because my Detroit Diesel has a high flow fuel system, once the engine starts it needs a high flow, also the Balkamp fuel pump has a fine screen in it. Without the check valve the screen could foul and stop your fuel flow. the Racor has a much larger capacity so this is less likely to happen as long as you have the check valve bypassing the fuel pump.

Then your Racor or other primary filter with a compound gauge (plus and minus 15 psi, about $9, Part Number 4004K41, McMaster Carr, 404 346-7000) on the inlet and another identical gauge on the outlet. These gauges tell you when it is time to change your filter (and sometimes more importantly, when you don't have to) and what is going on inside the pipes.

After the outlet of the Racor I have a valve to lead the fuel to the return line (for cleaning your fuel before starting the engine) and another valve to atmosphere (to obtain clean fuel in case you need some). The ball valve on the return lines to the tanks is so you can select which tank to return the fuel to, to seal off the fuel tanks and to pressurize the system to find leaks. The electric pump allows you to push fuel around to clean the fuel, fill the Racor, flush air from the system and pressurize the system to test for leaks. The gauges tell you what is happening inside the pipes. Air, water or other contaminants in the fuel have caused almost all of my diesel engine stoppages. The above set-up will go a long way toward reducing this.

A remote switch at the starter switch to operate the fuel pump before hitting the starter usually assures good fuel to the injector pump at spin-up time. I also have a electric pre-start lube oil pressure pump to supply the engine with lube oil in the bearings before I hit the starter. Also have a starter switch at the engine to avoid having to have two people to spin the engine.

Noting the normal operating pressures on the various gages while operating with new filters, and as the filters gradually be come more and more plugged with garbage, will reveal exactly when a filter must be changed and more importantly, when it is not that filter's time to be changed so you can look elsewhere for a problem. Mark the gauges with red and green magic markers. Making everything as easy as possible while tied to the dock, will pay off big time on a dark and stormy night offshore.

Generally, main engines and gensets should be completely separate systems so the main engines will not suck too hard and starve the genset. However, on Bandersnatch I have used 1/2" copper, (sweated and compression fittings), with the system splitting to a Racor 1000 feeding the GM 6V-53 and a Racor 500 feeding the Northern Lights 8Kw downstream from the electric pump. If I try to go steaming speed with the main engine the genset is starved for fuel and shuts down.

[Reply to someone objecting to pressurizing a fuel system] From a safety aspect though I would rather suck air than spew fuel. With 5-7 psi the fuel does not "spew" but dribbles or oozes from leaks and does so only when the system is pressurized by the electric pump, which in not on during normal operation but only when polishing, priming, bleeding, testing, etc. Sucking air will prevent most engines from starting and stop many operating engines. "Spewing" fuel will be very unlikely to catch fire since there is nothing hot enough in the engine room to ignite it. I have had my body completely inside each of my fuel tanks, sitting in an inch or two of diesel fuel, using a propane torch to solder fuel lines and was perfectly safe.

Pressuring would never have let me find them, but they would have been there when running the engines. If the pump is just downstream of the tank suction valve, where it should be, you would run the pump with the return line valve closed until the pump almost stops at about 7psi, then close the suction valve and turn off the pump. This will pressurize everything between the suction valve and the return valve to 7psi. At this point examination with a dry paper towel will reveal any leaks by converting invisible air suction leaks to visible drops of fuel.

The compound gauges I use in the primary filter area of my fuel system are: McMaster-Carr Supply Co - (404) 349-9700 PN 4004K41 compound pressure & vacuum gauge 15-0-15 psi $8.18 (in 1993) They do have them that go higher than plus 15psi but that is all I needed for my fuel system. You must use a liquid-filled gauge for the secondary filter on the engine because the vibration of the engine will destroy a dry type gauge.

In a message dated 2/27/99 8:12:02 AM Eastern Standard Time, writes: " If run under pressure, a differential pressure gage must be used to detect a plugging filter."

A differential gauge is expensive and not needed. Two compound gauges, one each at the input and output respectively of the filters works better because they give you more information to give you a clearer picture of the absolute pressure in the lines. I had an air leak in my fuel system some time ago. It did not affect the GM main engine since it has a circulating fuel system that pumps gallons of fuel through the unit injectors per minute and just sweeps the bubbles through and back to the tank.

However, the Northern Lights generator has a normal style injector pump and the filters finally filled up with air and stopped the generator. I pressurized the fuel system with the electric pump, as described, to about 7psi. I wiped down the entire (now pressurized) system with a paper towel. I popped a beer and visited a neighbor. When I returned I examined the plumbing carefully with a very strong flashlight and found fuel drops on the electric fuel pump by-pass checkvalve. The in and out fittings were dry. I dumped the pressure, unscrewed the bonnet and put on a new o-ring. No further problems.

It is also a GOOD THING to have an electric fuel pump available to push fuel through a dirty filter in an emergency when the sounds of breaking seas are getting louder and louder and you really, really, really, don't have the time to change filters and re-prime the system just then.

"I don't want to burst your balloon but be careful when you use Teflon tape. Do not cover the first thread with it! If you do pieces of the Teflon will come off and clog any orifices that might be in line. Also any strainers that you might have. Teflon tape is not to be used on ANY gas connections for this reason. I have a plumbing business thus I know from where I'm coming. - Andy"

Andy certainly know whereof he speaks. I used Teflon tape early on in a hydraulic system on Bandersnatch and spent some time tearing down the pump to find a bit of it in the check-valve holding it open and thus disabling the pump. However, I have seen Teflon tape used in commercially installed hydraulic systems. The trick, as Andy says, is to keep from getting bits of it in the system. Andy says at least one thread back, I say two. Thread compound will work, but tape is so much handier and neater. I suggest using lanolin on the deckplate threads. If you use Teflon on a fitting that you install and remove the tape gets cut up into pieces each time you install it so you have to remove all the pieces and do it again each time. Be very careful using silicone grease, "diver's grease", as it can dissolve some plastics.

Some engine stoppages were due to plugged up seawater strainers. The first sign that seawater stoppage is happening is that the rubber exhaust hose will overheat. Because of thermal inertia the block will not heat up as fast. If you are lucky you might smell burning rubber and shut down before the hose is completely destroyed. A low-cost wonder is to buy a little Klixon type thermoswitch for each engine. The ones I have are normally open temp switches that close at 120 degrees F. They are less than $10 and I got mine at Graingers (White-Rodgers 3F01-121 fixed setting snap disk fan control, close 120deg F, open 110 deg F), but any HVAC parts place will have them. They are held against the hose with a spring around the hose near the manifold. This is the first place to get hot when you loose seawater flow.

The generator one shuts the engine down (it did so yesterday due to weeds in the strainer), but the main engine one rings an alarm. To do the same with the block, there are idiot light switches available. But I prefer Murphy Gauges, a series of various gauges with an adjustable contact point or points that you can set to any temperatur/pressure/etc to sound an alarm or do a shut-down. Not low-cost but worth every penny.

My most useed of these is the main engine block cooling water temperature Murhphy Gauge which I set to 185-190 deg F to give me an early warning for main engine block overheat. This saved my butt when I got a leaky radiator cap and the engine overheated at cruising speed in the Chesapeake. I just eased the throttle to slow ahead and the engine cooled down. I then raised the throttle bit by bit until the temp started to rise again and then backed down a bit. Next port I got a new cap and problem solved cheapest, safest and most convieniently.

Another low-cost wonder is putting a strainer just downstream from your engine cooling seawater pumps. These rubber vane pumps shed bits of their rubber vanes when failing. Put an ordinary water strainer, could be plastic or bronze or S.S. just downstream from the engine cooling seawater pumps to catch the rubber bits before they get into the heat exchanger and exhaust cooling nozzle in the exhaust elbow, both of which are MUCH harder to clean out than the strainer. The strainer also acts as a watchdog on the condition of the seawater pump for troubleshooting. If there are no rubber bits, then the pump is not the problem. If the vane is starting to shed then you have early warning. You may then continue to operate if need be, and choose a convienent time to replace the impeller. Be aware, rubber parts can have an shelf life about the same as the operational life. So it may be a better to change rubber parts periodically rather than carry spares.

If you have a good impeller part number and source, a phone call and FedEx is often better than carrying spares of this type of part. A piece of duct tape around the shaft area of the seawater pump will corral the seawater when [notice I said 'when', your seawater pump seal fails to prevent the salt water from being flung into your alternator and releasing the magic smoke. I eventually replaced the duct tape with a bit of vinyl plastic. A stainless u-shaped piece of sheet metal would be nice too. It probably needs to be cut in a banana shape. make a paper template first.

A couple of fixed gooseneck lights in the engine space, shining on the places I work on the most has reduced the number of teeth marks on my flashlights. These small bits of easy engineering will eliminate some major sources of grief and make the boat life more fun. I'm sure you can come up with some great ones yourself. Remember that your boat is very much a work in progress, and can be greatly improved by engineering your way out of problems as you encounter them.

If anyone has any specific questions please contact me.


S/V Bandersnatch

Lying 30 07.7N 081 39.6W Julington Creek Estuary FL