Diesel engines are efficient, durable and the engine of choice for heavy equipment and boats. If you’re a boat operator, you’re probably no stranger to diesel engine fuel problems. It’s important to know the signs of trouble as soon as they begin.

How to Spot a Problem in Your Boat’s Diesel Engine Fuel

Here are some of the most common diesel engine fuel problems you’re likely to encounter:

Deposits in the Combustion Chamber

Conventional gasoline burns more cleanly than diesel, which means diesel engines are prone to developing deposit buildups. This reduces the total usable volume of the chamber and makes it more difficult to achieve optimum fuel burn when needed.

Difficulty Starting in Cold Weather

Diesel fuel contains paraffin wax, the molecules of which stick together in “crystals” that get larger as the outside temperature drops. This makes marine diesel engines difficult to start in the winter. Using diesel fuel with a higher cetane rating helps, as does certain fuel treatments designed to raise the cetane value.

Diesel Fuel Contamination

It’s possible you may end up filling your boat with contaminated diesel fuel. When this happens, it can cause clogged fuel pumps and inconsistent performance from the fuel pump.

Here’s what to know about bad diesel fuel symptoms and causes:

1. Fuel contamination may be caused by the infiltration of metal particulates or water introduced during the refinement process.

2. Diesel fuel does not have an inexhaustible shelf life. Diesel fuel that has degraded or “gone bad” is fuel that is outside its shelf life.

3. High-sulfur diesel fuel usually lasts no longer than a year. Bad diesel fuel is recognized by its dark and cloudy complexion.

Black Diesel Engine Smoke

If your boat’s engine is issuing black smoke, it’s a sign that the fuel isn’t burning completely. Usually, diesel engines exhaust water and CO2 as byproducts of their operation.

This problem arises from restricted airflow, which in turn may be caused by turbocharger lag (typically in older boats), problems with fuel injectors or valve clearances. Engine deposits can cause black smoke as well.

Black Diesel Fuel Problems

The term “black diesel” refers to the practice of using castoff motor oil as fuel for diesel engines. This isn’t recommended, as deacidifying used motor oil requires time, know-how, equipment and patience.

Experienced mechanics sometimes report success operating their marine engines this way, but the practice runs the risk of damaging fuel lines and injectors and causing more engine damage.

Additional Signs of a Diesel Engine Problem

Besides expired or contaminated fuel, there are other common diesel engine troubles to look out for:

Oil oxidation: Marine diesel engines left sitting for long periods of time run the risk of air infiltrating the oil, which can cause faltering and outright failure of the engine. At most temperatures, it’s wise to change the oil before using a boat that has sat unused for six months or longer.

Hard starting: If a boat cranks longer than you expect as you start the engine, it’s wise to check the compression and fuel delivery components.

Loud noise during operation: Diesel engines tend to be louder than their gasoline counterparts. But extra-loud engine knocking may indicate trouble with your boat’s fuel injectors.

How Hubei July Can Assist You

Need help diagnosing marine diesel engine fuel problems or buying replacement parts? Contact the Hubei July team today. We’d be happy to help you find the parts you need quickly.