Petrol engines
The condition for an accurate check is a serviceable charged battery.
Remove the fuel return hose (2) from the distribution pipe by loosening the clamp.
Caution: The fuel system is under pressure. Collect any leaked fuel with a rag. Clamps must be replaced after being loosened.
Note: Some models have the fuel supply line screwed directly into the distribution line. In this case, the sealing ring must always be replaced during installation and lubricated with technical petroleum jelly. In other designs, the fuel hose is secured with clamps and a special tool is required to release them. Before installation, check the sealing ring and replace it if necessary.
Place the return fuel line from the expansion pipe into a measuring vessel with a capacity of approximately 2 liters.
Remove the fuel pump relay. The relay is located in the relay box on the rear left side of the engine compartment.
In the relay socket, short-circuit contacts 30 and 87 with an auxiliary wire with a diameter of 1.5 mm and let the fuel pump run for about 30 seconds.
The pump should deliver about 1 liter of fuel in 30 seconds. The current consumed by the pump during operation is about 9.5 A.
If too little fuel is supplied, replace the fuel filter and check the performance again. If it is still low, replace the fuel pump.