Fuel pressure

The fuel pump, pumps the fuel from the fuel tank through the filter to the fuel rail and then into the cylinders via the injectors. The pressure of the fuel is controlled by the fuel pressure regulator on the end of the fuel rail. The fuel pressure regulator works with vacuum from the engine. The faster the engine goes the less vacuum it creates in the manifold which means that the regulator would be closed more. When the regulator closes it creates a higher pressure in the fuel line (by restricting the flow or blocking off the fuel at the end of the fuel rail)  which forces more fuel through the injectors into the cylinder.

Experiment


We connected a fuel pressure gauge to the fuel line after the filter. We started the engine and checked the gauge the reading was about 2.5 bar when we revved the engine the pressure increased to about 3 bar. To simulate the engine at full speed the vacuum hose can be disconnected from the fuel pressure regulator.

Reflection


The fuel pressure gauge can be used to see if the fuel pump is working and to check if the fuel pressure regulator is working properly. when the engine is idling and then the regulator vacuum hose is removed the pressure should increase in the fuel line. If it remains the same there may be a problem with the fuel pressure regulator. A flow test is done to see how much fuel is pumped out over a certain amount of time. The fuel supply pipe is disconnected and placed in a bottle or any other container then the time it takes to fill up is measured. The flow rate is equal to the amount (size of the container) divided by time (how long it takes to fill up the container)

Fuel pressure gauge

Gauge at idle speed