4.7 Fuel Injectors (CIS, CIS-E and CIS-E Motronic)The mechanical fuel injectors used are actually precision nozzles. Above a certain minimum pressure, the injector nozzles open and continuously deliver atomized fuel into the engine's intake ports. The injectors are mounted in two-piece inserts which thread into the cylinder head (into the intake manifold runners on 16-valve engines). The injectors are held in place in the inserts by thick rubber O-rings. A typical injector, its two-piece insert, and the sealing O-rings are shown in Fig. 4-27.
The most common problems associated with fuel injectors are low fuel flow rate or uneven spray pattern, both caused by carbon deposits built up around the discharge nozzle or by contaminated fuel. Some signs of faulty injectors are hard starting, rough idle, and detonation (pinging) under load. Keep injectors functioning properly by keeping them clean. See LUBRICATION AND MAINTENANCE for information on fuel filter maintenance, and on the fuel additive which Volkswagen recommends for reducing and preventing carbon deposits. |