Diesel fuel pumping problems

Contamination of fuel with high-viscosity products or operation at excessively low temperatures can increase the viscosity of fuel and result in fuel pumping problems. Also, if diesel fuel viscosity at 0°F (-17.8°C) is greater than 45 cSt, fuel pumping problems are likely to occur. 

For a long time the official specifications for diesel fuel set only a mciximum viscosity of 9.5 mm /s at 20°C. Henceforth, a range of 2.5 mm /s minimum to 4.5 mm /s maximum has been set no longer for 20°C but at 40°C which seems to be more representative of injection pump operation. Except for special cases such as very low temperature very fluid diesel fuel and very heavy products, meeting the viscosity standards is not a major problem in refining. 

Dual-phase extraction cannot remediate heavy chlorinated compounds, pesticides, or heavy hydrocarbons including polychlorinated biphenyls (RGBs), dioxin, fuel oil No. 6, or metals (with the possible exception of mercury). High-velocity pump systems (such as liquid ring vacuum pumps) tend to form emulsions, especially when diesel fuel is part of the recovered fluids. The problem of emulsion can be solved with prepump separation or a de-emulsification unit. 

At low temperatures, the wax in most distillate fuels can cause severe problems with fuel pumping and filtration. As diesel fuel cools, wax begins to crystallize and become visible. The temperature at which crystallized wax becomes visible is known as the cloud point. 

PROBLEM DIFFICULTY IN PUMPING DIESEL FUEL AT LOW TEMPERATURES / FUEL FILTER PLUGGING... 

Leakage past diesel fuel injection pump plunger in worn equipment may occur can result in hot restart problems whereby fuel leaks past the injection plunger in hot equipment restarting may be impossible until the engine cools down. 

Engine oil dilution is a potential problem with biodiesel since it is more prone to oxidation and polymerization than diesel fuel. The presence of biodiesel in engine oil could cause thick sludge to occur with the consequence that the oil becomes too thick to pump. Special formulations of engine oil are being developed to minimize the effects of dilution with biodiesel. 

The addition of ethanol to diesel lowers fuel viscosity and lubricity. Lower fuel viscosities lead to greater pump and injector leakage, reducing maximum fuel delivery and hence power output. Hot start problems may also be encountered as insufficient fuel may be injected at cranking speed when fuel leakage in the high-pressure pump is amplified because of the reduced viscosity of the hot fuel. 

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