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Tool 7: Maintenance

The fuel injection system and the distributor system differ with the age of the vehicle and whether it uses diesel or petrol fuel. Older vehicles have mechanically-controlled injection and distributor systems that require regular checks and need to be adjusted manually to “tune” the engine.


Modern trucks and cars (typically trucks manufactured after 1994 and passenger cars manufactured after 1990) have electronic injection systems that adjust themselves automatically several times per second. These vehicles can not be “tuned” manually. However, there are still several parts of the fuel injection and distributor system that need to be checked and replaced if they are old and worn down. Parts of all electronic fuel injection systems that can be worn out are the fuel pump (the heart of any electronic fuel injection system), the injector, and the pressure regulator. Parts that typically need replacement or cleaning in diesel vehicles are the diesel nozzle and the injector.


The items that need to be replaced on a regular basis in all vehicles – both old and modern – are the spark plugs, air filter, fuel filter, and some emission control filters. When changing the oil, it is essential to use good quality, energy-conserving oil with a viscosity grade that is consistent with the grade specified in the vehicle operating manual. Ask at your garage or at a well-equipped pump station for the correct oil grade. When spark plugs are replaced, the technician should check the ignition wires and the cap and rotor if your car/truck has them.


Heavy black smoke coming out of a tailpipe is a well-known sign that the vehicle has a malfunctioning diesel engine. Black smoke results from overfueling diesel engines; this permits some extra power but consumes more fuel. In addition, black smoke can also be caused by driving in high altitude conditions. If you are constantly driving in high altitudes, it is important to have your vehicle tuned to these conditions. The most common causes of black smoke from diesel engines are dirty injectors and nozzle tip wear. Tuning the engine and making necessary repairs reduces emissions and improves fuel consumption.



Schoolbus (diesel) in Nairobi. Photo: Max Ahman


Tire pressure has a major effect on fuel economy, vehicle safety, and tire life. According to a study by the International Energy Agency (IEA), up to 30% of vehicles have one or more under-inflated tires. Poorly inflated tires can increase fuel consumption by several percentages. The IEA also estimates fuel consumption increases of 2.5-3% for every psi (pound per square inch) below the optimal tire pressure. Check the vehicle door stickers for minimum cold tire inflation pressure recommendations.


Wheel alignment: If your tire treads show uneven wear, then the wheels are not properly aligned. Wheels that are fighting each other waste fuel and wear out quickly. A quick look at the wear of your vehicle’s treads can indicate if the wheels are properly aligned. Wearing on just one or the other side of the wheel is a sign of poor alignment. A well-equipped tire center can align your wheels.

For more info on I&M >> www.cleanairnet.org

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