Rising Fuel Pump Problems and Main Perpetrator-Causes and Mitigation


Marine machinery problems due to bad quality fuel had grown tenfold in recent past in spite of the tumbled fuel prices. Substandard contaminated fuels are supplied that jeopardize the safety of the crew and the ship.

Recently more Fuel pumps and allied systems such as Fuel Pump Injectors are affected to a large extent mainly due to bad quality of Fuels. Not only Fuel pump and Injectors are prey to this kind of bad fuels but also Fuel lines running to and forth are also affected badly due to blockage.

Signs of fuel pump issues and allied systems:

Primarily Fuel problems will not arise overnight. As soon as poor quality Fuel is put in use hint is given in the form of operational parameter deviation. As soon as the problem fuel is put in to use the following visible signs are witnessed which includes High exhaust gas Temperature, loss in mechanical efficiency (that can be found by indicator diagram), desired Engine load cannot be achieved, accumulation of unburned carbon deposits and soot in exhaust trunk at times result in surging with an owling noise from the Turbocharger turbine end, sticky and stuck Fuel rack. These are the few symptoms that will lead to Main engine problems.

The above signs will not narrow down primarily to a Fuel pump problem but a close vigil on the engine general functioning and few clues like stuck fuel rack will enable in ascertaining the cause and the likely impact on the specific part of the equipment.

Causes for the impact:

Fuel pump problems occur due to various issues which includes Lubricity problems due to Low sulphur, Presence of Xylene equivalence etc.

Predominantly the problems occur due to Xylene Equivalence. Xylene equivalence at times mistook as component but it is a Tendency number while blending the Fuel for viscosity and other parameters. As per Class NK “Guidance for Measures to Cope with Degraded Marine Heavy Fuels Version II” states that as aromatic components in fuel increase, the xylene equivalent becomes smaller and stability increases but combustibility will deteriorate, making it difficult to evaluate fuel performance. When the xylene equivalent becomes greater than 30, problems are likely to occur. The higher the density of oil, the greater is the xylene equivalent; the higher the density of oil, the poorer is the blending stability, and it has been suggested that the probability of sludge deposition also increases. Viswa Lab’ Fuel problem support group had witnessed that Xylene equivalence more than 30 is expected to be affecting the Fuel pumps resulting in sticky plunger and barrel. The above said combined with the symptoms of profuse sludge formation in the Purifier bowls with frequent desludging. At times purifiers need to be overhauled frequently. Filters will be alarming very frequently. The above symptoms are witnessed usually.

Remedies or Steps followed to mitigate the issue:

Xylene equivalence is a very critical number that cannot be completely reduced but can be restricted to a certain extent in the following ways:

Blending-Extremely good stable fuel, if available, with substantially less Xylene equivalence number will enable us to burn the Bad (high xylene equivalence fuel) bunkers without any issues.


To counter tract high xylene equivalence, the most effective solution is to blend with a good stable fuel. Before blending the compatibility of the Fuel need to be tested whether the two fuels can be mixed and under what ratio’s. Upon ascertaining the ratio’s, mixing need to carried out in the settling tanks not in the bunker tanks to restrict the impact if the Two fuels don’t go well along with each other. Once the Two fuels are mixed appropriately while consuming the fuel the operational condition need to be monitored. A close vigil on the operational parameters will enable us to understand if any issue prevails.

To conclude, Xylene equivalence can be reduced by comingling with extremely good stable bunkers with less xylene equivalence number.

Viswa Lab is dealing on daily basis with large volume of samples, across the globe, with high xylene equivalence number and dealt successfully with various Fuel pump problems. For further info, please contact [email protected]


  1. Sir,
    In the past you had published an article detailing what is required for a ship / owner to be ready for the new fuel on board – like tank cleaning etc. There were some 20 points. Can you e-mail it to me please. Aziz Ansari


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