Fuel System

Why is it important to maintain your Fuel System?



It is the goal of proper maintenance practices, which includes effective filtration, to keep the system clean and help ensure the most economical and efficient fuel system life. Some of the ways contaminants can be kept out of the system from the onset are by keeping fuel transfer equipment like nozzles, tanks and hoses free from surface dirt and out of the rain, and by using filtration at the pump. Proper storage techniques, such as keeping storage tanks covered to minimize temperature fluctuations, also reduce the impact of contamination.

The keys to maintaining the fuel tank are periodically check for free water in the tank, visually inspect the tank exterior and connections for rust and inspect the interior for signs of corrosion or algae growth. If contamination is present, the tank must be drained and cleaned. If algae is found, a commercially available biocide can be used to kill it, and then the tank must be drained, rinsed and refilled with clean fuel.


Suitable filtration includes using a fuel filter and/or fuel/water separator and changing them at recommended intervals. The purpose of the fuel filter is to remove unwanted contamination before it reaches the other components of the fuel system.

There are two types of fuel filters, primary and secondary. Typically, the primary filter is considered the suction side filter and the secondary filter, the pressure side. The primary filter is upstream of the fuel pump and the fuel is pulled (suction) through the filter. Its function is to catch contaminant before the fuel flows through the fuel pump. The secondary filter is downstream of the fuel pump and fuel is pushed (pressure) through the filter. Its main function is to capture contaminant in the fuel before it flows into the injection pump assembly.

Some engines require a primary filter, some require only a secondary filter and some require both. In some cases, in place of a primary and secondary filter setup, a more efficient fuel/water separator is used, as is the case on Cummins engines. The primary filter, or fuel/water separator, will be found on the suction side or before the fuel pump. As mentioned before, water gets into the fuel as a result of natural condensation, leaking fuel storage tanks and so on. It can be in the form of large droplets, or it can be emulsified in the fuel. The water must be removed to achieve maximum performance and maximum life from the engine. Fuel/water separators are designed to provide both filtration and water removal. Use a fuel/water separator in place of a fuel filter or in conjunction with a fuel filter to remove water as well as contaminants from the fuel system.

Fuel additives are intended to disperse contaminants, clean components, increase fuel lubricity and decrease extreme temperature effects — all impacting filter and component life. Competitive products have varying degrees of success in relation to their claims, depending on the formulation.

Some products provide a gauge that tells you when to change the primary or suction side fuel filter. Service intervals of fuel filters vary due to factors such as fuel quality, temperature and filter size. The fuel filter restriction indicator gives the operator an easy-to-read gauge that gives feedback on the remaining life of the fuel filter. Finally, use diesel fuel analysis for troubleshooting a fuel-related problem. Fleetguard offers different test packages that include testing for calculating the cetane number, gravity, distillation, viscosity, cloud point, flash point, sulfur, carbon residue, water & sediment, fuel stability and more, and that give specific recommendations based on the results. Remember that the fuel system is the heart of a diesel engine. Keep it functioning properly through proper maintenance practices, and you will be assured of long, trouble-free life.