5.1 Test Method—Deposits are prone to form on the metering surfaces of pintle-type electronic fuel injectors. These deposits reduce fuel flow through the metering orifices. Reductions in metered fuel flow result in an upset in the air-fuel ratio, which can affect emissions and driveability. When heavy enough, these deposits can lead to driveability symptoms such as hesitation, hard starting, loss of power, or a combination thereof, that are easily noticed by the average driver and lead to customer complaints. The mechanism of the formation of deposits is not completely understood. It is believed to be influenced by many factors, including driving cycle, engine design, port fuel injector design, and composition of fuel used. The procedure in this test method has been found to build deposits in injectors on a consistent basis. The deposits formed by this procedure are similar to the deposits experienced in the field in terms of composition and in amount of deposition. This procedure can be used to evaluate differences in unleaded base fuels and fuel additives.
5.1.1 State and Federal Legislative and Regulatory Action—Legislative and regulatory activity, primarily by the state of California and the Federal Government necessitate the acceptance of a standard test method to evaluate the port fuel injector deposit-forming tendency of an automotive spark-ignition engine fuel.
5.1.2 Relevance of Results—The operating conditions and design of the engine and vehicle used in this test method are not representative of all modern automobiles. These factors must be considered when interpreting test results.
