In order to perform properly, fuel pumps need a specific amount of pressure (measured in PSI), and fuel pumps are pressure-tested to ensure they fall under the crucial PSI range. Today, the majority of fuel-injected engines need pumps capable of keeping pressure levels in the 40–70 PSI range. To perform a pressure test, mechanics utilize a fuel pressure gauge which they connect to the fuel rail or test port. Then, when you fire up the engine, the gauge reflects the pressure created — in real-time — by the fuel pump. Low readings compared to the manufacturer’s recommended PSI can indicate either pump failure or blockages in the fuel system.
Stable fuel pressure is vital for the engine control unit (ECU) to maintain optimal air-fuel ratios on vehicles equipped with electronic fuel injection. A pressure test results in a steady reading but any variation greater than 5% means the pump is likely having difficulty maintaining pressure, which can impact engine performance, and fuel economy. If that pump is supposed to run at 50 PSI, and it only gets to 45 PSI, the engine will be down on power when he puts his foot down, too. The decrease does not only reduce engine output, however, it also affects emissions because incomplete combustion often increases hydrocarbons.
Another frequently performed test is a “deadhead” pressure test where the fuel line is momentarily blocked to determine maximum output pressure of the pump. This test indicates whether or not the pump is able to generate its rated flow, which is particularly important in situations of extreme performance where fuel demands are above normal levels. The deadhead, in other words not through a fuel return line, test will show mechanics that most fuel pumps are good to above 90 PSI; anything less could indicate wear on the pump and internal damage, leading to fuel delivery failure.
As fuel pump expert Ed China puts it, “steady pressure is the foundation of effective fuel delivery.” It goes without saying that any vehicle — especially older vehicles — should be pressure-tested as regularly as possible.
Pressure-testing equipment must be regularly calibrated to ensure accurate results and an effective performance baseline. A new Performance Fuel Pump safeguards the vehicle against fuel system deficiencies, maintaining pressure for daily driving and peak performance to prevent fuel system problems.