As most of us know, good clean fuel is important to any diesel engine. Because of this, it is important to do proper routine maintenance to the fuel system to keep your engine performing well. A few simple inspections will help keep the fuel flowing and prevent engine failures or performance issues.
Keeping water and dirt from ever getting into the fuel tank and fuel system is the first step to maintaining a healthy fuel system. Checking the fuel source is not always easy to do, but there are some precautions that can be taken to help ensure clean fuel goes into the tank. Getting fuel from a reliable source is the first step. Try to fuel from marinas or other sources that have a high turnover in their fuel supply. Avoid fueling from a storage tank that contains old fuel or is near the bottom of the tank. If the source is suspicious, put a small sample into a clear container for visual inspection prior to filling your tank.
Next, make sure water cannot get into the vessel’s tank from outside sources. Water can enter through the fill plate on deck, the tank vent and even from the air in the tank. It is good practice to inspect the fill plate and cap every time fuel is put aboard. Take a few seconds to inspect the cap and seal for damage or wear. If anything does not look right, it should be fixed as soon as possible.
Often ignored, tank vents and fittings can cause problems either by letting water into the tank or by preventing air from getting into or out of the tank. Make sure the vent hose has a loop above the tank top to prevent any water entering the vent from making it to the tank. The vent itself should be located high and in a place that will not allow seawater or rainwater to enter.
Tank vents have to allow air out of a tank when fueling as well as let air into the tank as fuel is withdrawn during engine operation. If while fueling the fuel flow is slow or air “burbs” from the fill, there may be a problem with the vent and fittings. I have seen tanks collapse during use when a clogged vent would not allow air into the tank when running the engine. I have also seen many engines mysteriously lose RPM and run poorly because the fuel supply has been restricted by a vacuum in the tank. Insect nests and wood chips or debris from rubbing on a dock can completely block air from entering the tank. Routine inspections of the vent, fittings, hoses, and any anti-spill devices fitted will help prevent these issues.
Although air is needed in the fuel tanks, it can be a double-edged sword because it brings moisture in with it. This moisture can then condense on the inside of the tank during temperature changes. Keeping the tanks full of fuel, particularly during periods of layup, will go a long way to reducing this problem.
If the filters are often clogged or dirty, it may indicate there may be contamination in the tanks and fuel polishing could be in order. “Polishing” is filtering the fuel by cycling it through large filters. This is usually done by placing a pick tube into the tank as close to the bottom as possible and using a high-volume pump to run the fuel through the large filters and then back into the tank. The fuel is cycled through the filters until it is clean. There are many professional services that specialize in doing this.
Often fuel tank contamination goes unnoticed until the vessel encounters rough weather with larger seas and vessel motion stirring up water and sediments in the tank’s bottom. Of course, bad weather is also the worst time to encounter a clogged filter and engine shutdown. This is why it is important to make sure your fuel and tanks are clean prior to voyaging.
Fuel lines and connections are equally important to any fuel system and should also be inspected regularly. All fittings, along with the fuel lines themselves, should be checked along their full run from the tank to the engine. Look for signs of wear and chafing, particularly near moving or vibrating parts. Rubber hoses in particular need to be checked for wear and damage from abrasion. Metal piping can also fail because of abrasion and may also suffer from corrosion issues. If rubber fuel lines are over 10 years old, consider replacing these as rubber fuel hoses can fail internally, causing poor fuel flow or complete blockage. When replacing fuel lines, use marine grade hose that is USCG approved for fuel use. Approved hoses will be labeled on the outside of the hose. Hoses should be clearly labeled “A1-15,” “A1” or “A2.”
While checking the fuel lines, be sure to check all of the fittings and connections as well. Hoses should only be connected to other fittings with a hose barb or swaged fitting. Hoses should never be slipped over smooth tubing or pipe fitting, with or without threads, as this can lead to leakage or the hose slipping off the tube. Hose clamps should be properly sized and in good condition. Clamps that are too large for the hose can cause the hose to become egg-shaped and lead to leakage. Flare-type fittings should be checked for cracks in the flare nuts and that the nut is tight. All fittings should be checked regularly for leaks.
Inevitably, some water and dirt will get into even the best-maintained fuel systems. Good primary and secondary fuel filters will keep the engine running smoothly as long as they are clean. Some fuel filters can be equipped with water alarms and vacuum gauges. I consider these a requirement for long distance offshore passages. Regularly check the filter bowls for water and sediment. Pay extra attention anytime the boats have been in heavy seas that can stir up dirt and water in the tanks.
When talking about fuel filters, it is important not to overlook the secondary fuel filters usually mounted on the engine just ahead of the injector pump. Secondary filters are there not only to catch any contaminates that slipped by the primary filters but to do a final filtering to remove smaller particles that the primaries will not. These filters are usually not changed out as often as the primaries but still need to be replaced regularly. This is more important if the primary filters were found to have heavy water or other contaminates in them.
A clean, well-maintained fuel system will keep all the engines running smoothly, but it takes a bit of due diligent and time from the captain. It is always better to catch a problem at dock before it becomes a problem at sea, so a few simple checks along with care with what is put into the tanks will help keep the motors going when they are needed the most.
