What this test proves

Verify fuel supply pressure at the specified point. Pressure alone does not establish adequate delivery volume.

Tools

  • Fuel-compatible pressure gauge or transducer rated for the low-pressure system
  • Correct adapters and fuel containment
  • Scan tool and OEM specifications

Preparation and precautions

  • Identify fuel type and the low-pressure circuit. Never attach this equipment to a GDI or diesel high-pressure rail.
  • Work with ventilation, eye protection and ignition sources controlled. Depressurize by the vehicle procedure before opening a connection.

Connections

  • Install the specified adapter at the approved low-pressure test port or supply connection. Keep fuel outside the passenger compartment.

Equipment settings

  • Select the correct pressure range and units. Confirm whether the specification is absolute, gauge or manifold-referenced pressure.

Test sequence

  1. Inspect for leakage after connecting.
  2. Command the pump or perform the prescribed key-on prime.
  3. Record prime, idle and any specified operating-condition readings.
  4. Check pump supply, command and restrictions if pressure is incorrect.
  5. Depressurize before removing equipment; restore connections and check for leaks.

Expected signal / readings

Pressure should reach and maintain the application’s target under its stated conditions. Returnless and vacuum-referenced systems behave differently.

Interpreting results

  • Low pressure can involve pump power, regulation, restriction, leakage or the pump.
  • Normal static pressure does not prove adequate flow under demand.

Common mistakes

  • Applying a port-injection specification to direct injection
  • Ignoring gauge versus absolute units
  • Opening a pressurized fitting