Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Fuel Pump Pressure Test
Use this test in conjunction with the FUEL PUMP CAPACITY TEST , DIAGNOSIS AND TESTING - FUEL PRESSURE LEAK DOWN TEST and FUEL PUMP AMPERAGE TEST .
The fuel pump contains a one-way check valve to prevent fuel flow back into the tank and to maintain fuel supply line pressure (engine warm) when pump is not operational. It is also used to keep the fuel supply line full of gasoline when pump is not operational. After the vehicle has cooled down, fuel pressure may drop (cold fluid contracts), but liquid gasoline will remain in fuel supply line between the check valve and fuel injectors. When the electric fuel pump is activated, fuel pressure should immediately (1-2 seconds) rise to specification.
The fuel system is equipped with a separate fuel pump mounted to the chassis along side of the fuel filter/pressure regulator. The fuel filter/pressure regulator is not controlled by engine vacuum.
- Remove the protective cap and connect the 0-6.9 bar fuel pressure gauge (2) to the fuel rail service test port pressure fitting (1) on the fuel rail (3). The DRB® III Scan Tool along with the PEP module, the 34.4 bar pressure transducer, and the transducer-to-test port adapter may also be used in place of the fuel pressure gauge.
- Start and warm engine and note pressure gauge reading. Fuel pressure should be 3.7 - 4.2 bar (54 - 61 psi) at idle.
- If engine runs, but pressure is below 3.7 bar (54 psi), check for a kinked fuel supply line somewhere between fuel rail (3) and fuel pump. If line is not kinked, but specifications for either the Fuel Pump Capacity, Fuel Pump Amperage or Fuel Pressure Leak Down Tests were not met, replace the fuel pump. Refer to REMOVAL .
- If operating pressure is above 3.7 bar (54 psi), electric fuel pump is OK, but fuel filter/pressure regulator is defective. Replace fuel filter/pressure regulator. See FUEL FILTER/PRESSURE REGULATOR .
- Install the protective cap to the service test port pressure fitting (1) on the fuel rail.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.