5.1 Idle Speed and Maximum RPM Adjustments

Although the fuel injection pump is self-lubricating and long-wearing, some wear occurs. Over time, periodic adjustment of the idle speed and maximum rpm may be necessary. Adjustments are also necessary if a new pump is installed.

Because the diesel engine has no electrical ignition system, special methods and equipment are required to be able to measure engine rpm. Volkswagen special tool no. VW 1367 measures rpm by detecting timing marks on the engine's flywheel through an access hole in the top of the bellhousing. VW 1324, shown in Fig. 5-1, is another Volkswagen special tool which converts engine vibrations to electrical signals which can be read as engine rpm with a conventional tachometer. While the latter method is much less expensive, the cost may still make dealer service a more cost-effective alternative.

Fig. 5-1.

Tachometer connected to diesel rpm sensor, Volkswagen special tool no. VW 1324.