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Cleaning and Testing Injectors

A special tool for bench-testing and cleaning fuel injectors is shown in Fig. 4-32. Remove the injector from its fuel line and install it on the tester line as shown. Pump several times to purge the air from the line. To check injector opening pressure, pump slowly and read the pressure on the gauge as the injector starts to spray. See Table f. Any injector which opens or leaks below the specified opening pressure should be replaced. Repeated use of the tester can be used to clean a slightly dirty injector, but any injector which continues to have an uneven spray pattern should also be replaced.

Fig. 4-32. Fuel injector pressure tester (Volkswagen special tool no. US 8034) used to clean and test CIS, CIS-E, and CIS-E Motronic fuel injectors.

Table f. Fuel Injector Opening Pressures


Use only Shell mineral spirit 135 or equivalent when testing or cleaning injectors using pressure tester. Shell mineral spirit 135 is flammable. Do not smoke or work near heaters or other fire hazards. Keep a fire extinguisher handy.

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