What this test proves

Measure fuel quantity delivered over time at the prescribed pressure. Free-flow volume is not equivalent to delivery under pressure.

Tools

  • Approved fuel-volume/flow tester and adapters
  • Approved collection equipment if the procedure requires it
  • Timer and OEM flow specification

Preparation and precautions

  • Follow ventilation, static-control and fire precautions. Use equipment compatible with the fuel.
  • Do not improvise an open container or open a high-pressure rail. Identify the correct low-pressure test location.

Connections

  • Connect the flow tester according to its manual and the vehicle procedure, including the specified return or containment arrangement.

Equipment settings

  • Set the specified backpressure and test duration. Use matching volume/time units.

Test sequence

  1. Check connections for leaks.
  2. Command the pump using the approved method.
  3. Measure delivery over the specified interval and pressure.
  4. Compare supply voltage and restrictions if delivery is low.
  5. Recover fuel and restore the circuit safely.

Expected signal / readings

Delivery must meet the vehicle’s minimum quantity over the specified time and backpressure.

Interpreting results

  • Low flow can involve a restricted filter/pickup, inadequate voltage, regulation or a worn pump.
  • An unrestricted flow result may conceal poor pressure capability.

Common mistakes

  • Ignoring test backpressure
  • Comparing different time intervals
  • Running the pump dry