FUEL INJECTION

To get an overall understanding of fuel injectionbasics, we're going to analyze the Bosch L-Jetronic fuel injection system, which was widely used on many automobiles made during the seventies and eighties. Some examples are BMW E21, E28, E30, the Beetle, Super Beetle, and VW Bus. Most of the complaints seem to stem from the fear of the unknown. Unfortunately, this fear results in the removal of a superior system from the engine and usually winds up with the owner replacing it with an inferior aftermarket carburetor setup.
In reality, the L-Jetronic system is very simple, very reliable, and easy to diagnose. All you need for diagnostic tools is a fuel pressure gauge, a multimeter, and a manual. The Bentley manual does an excellent job of explaining FI diagnostic procedures. Most people blame ignition system problems on the fuel injection and go on a parts-replacing spree, unnecessarily wasting money. So it is imperative that before diagnosing the fuel injection system, the ignition system must be in tip-top shape and the engine must be free of vacuum leaks.
This part of the home page endeavors to explain the functions of the various fuel injection parts so that the seemingly mysterious fuel injection system will be revealed for what it is: a bunch of simple parts working together.
Bosch L-Jetronic Fuel Injection.

For detailed troubleshooting information on your Bosch L-Jetronic system, check out the Bosch FI manual online, which is a scanned in Bosch L-Jetronic manual with great flow-charts for troubleshooting.