Fuel Pressure Test (Low Pressure System): Notes

WARNING: This page is about a different variant/trim than selected.

Release the residual pressure in fuel line (Refer to the Fuel Delivery System - Repair Procedures - "RELEASE RESIDUAL PRESSURE IN FUEL LINE ").
NOTE: When removing the fuel pump relay, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the GDS after completion of "Release Residual Pressure in Fuel Line" work.
Install the Special Service Tool (SST).
1. Disconnect the low pressure fuel feed tube from the low pressure inlet of high pressure fuel pump.
  NOTE: There may be some residual pressure even after "Release Residual Pressure in Fuel Line" work, so cover the hose connection with a shop towel to prevent residual fuel from spilling out before disconnecting any fuel connection.
2. Install the special service tool for measuring the fuel pressure in between the low fuel feed tube and the low pressure inlet of high pressure fuel pump (Refer to the figure below).
  
  Fig 1: Installing Special Service Tool For Measuring Fuel Pressure In Between Low Fuel Feed Tube And Low Pressure Inlet Of High Pressure Fuel Pump
  Courtesy of KIA MOTORS AMERICA, INC.
Inspect fuel leakage on connections among the low fuel feed tube, the low pressure inlet of high pressure fuel pump, and the SST components with IG ON.

Measure Fuel Pressure.

Start the engine and measure the fuel pressure at idle.

Fuel Pressure: 495 ~ 505 kPa (4.9 ~ 5.1 kgf/cm² , 71.8 ~ 73.2 psi)

NOTE: If the fuel pressure differs from the standard value, repair or replace the related part (Refer to the table below).

Fuel Pressure	Cause	Related Part
Too Low	Fuel filter clogged	Fuel Filter
Too Low	Fuel leakage	Fuel Pressure Regulator
Too High	Fuel pressure regulator stuck	Fuel Pressure Regulator

Stop the engine, and then check for the change in the fuel pressure gauge reading.

Standard Value: The gauge reading should hold for about 5 minutes after the engine stops

NOTE: If the gauge reading should not be held, repair or replace the related part (Refer to the table below).

Fuel Pressure (After Engine Stops)	Cause	Related Part
Fuel Pressure Drops Slowly	Leakage on injector	Injector
Fuel Pressure Drops Immediately	Check valve of fuel pump stuck open	Fuel Pump

Release the residual pressure in fuel line (Refer to the Fuel Delivery System - Repair Procedures - "Release Residual Pressure in Fuel Line RELEASE RESIDUAL PRESSURE IN FUEL LINE ").
NOTE: When removing the fuel pump relay, a Diagnostic Trouble Code (DTC) may occur. Delete the code with the GDS after completion of "Release Residual Pressure in Fuel Line" work.
Test End
1. Remove the Special Service Tool (SST) from the low pressure fuel feed tube and the low pressure inlet of high pressure fuel pump.
2. Connect the low pressure fuel feed tube and the low pressure inlet of high pressure fuel pump.