Malfunction: too high fuel consumption (Opel Kadett D)

Test condition: Size and type of tires correspond to standard equipment, easy wheel movement (brakes, bearings), the running-in is finished (approximately 5000 km). Accurately determine fuel consumption.

Malfunction	Reason/Remedy
The air filter is dirty, the fuel system is leaky	Clean or replace the filter element. Inspect all fuel lines (suction, return, injection), fuel filter and pump
The return line is clogged	Blow air through the return line from the fuel pump to the fuel side
Idle speed or maximum speed too high	Check and adjust idle speed and maximum speed
The injectors are faulty	The injector is leaking or dirty, the injector needle is loose or broken. Incorrect injection pressure. Defective or loose protective heat seal under the injector
Fuel injection start is not adjusted	Adjust
The fuel pump is faulty	Try installing a new pump
The engine has mechanical faults	Valves leaking. Worn cylinders/pistons, leaky cylinder head gasket. Narrowing in exhaust system. Check compression