Fuel Pressure Test

Reduce the internal pressure of the fuel lines and hoses:
1. Disconnect the fuel pump harness connector.
2. Start the engine and wait until fuel in fuel line is exhausted. After the engine stalls, turn the ignition switch to the OFF position.
3. Disconnect the battery negative (-) terminal.
4. Connect the fuel pump harness connector.
Fig 1: Identifying Fuel Tank Connections
Courtesy of KIA MOTORS AMERICA, INC.
Disconnect the high-pressure hose from fuel line.
CAUTION: Cover the hose connection with a shop towel to prevent splashing of fuel caused by residual pressure in the fuel line.

Fig 2: Disconnecting High Pressure Fuel Hose
Courtesy of KIA MOTORS AMERICA, INC.
Using the fuel pressure gauge adapter (OK3MS-131-001), install the fuel pressure gauge (OK2A1-131-001A) to the fuel line. Tighten the bolt to the specified torque.
Fuel pressure gauge to fuel delivery pipe bolt: 25 - 35 N.m (2.5 - 3.5 kg.m, 18 - 26 lb.ft)

Fig 3: Installing Fuel Pressure Gauge
Courtesy of KIA MOTORS AMERICA, INC.
Connect the battery' s negative (-) terminal.
Apply battery voltage to the terminal for the pump drive and activate the fuel pump. With fuel pressure applied, check that there is no fuel leakage from the pressure gauge or connection part.
Start and run the engine at curb idle speed. Disconnect the vacuum hose from the pressure regulator, and plug the hose end. Measure the fuel pressure at idle.
Standard value: 323 - 343 kPa (3.3 - 3.5 kg/cm² , 47 - 50 psi)

Fig 4: Testing Fuel Pressure Regulator With Regulator Vacuum Hose Disconnected
Courtesy of KIA MOTORS AMERICA, INC.
Measure the fuel pressure when the vacuum hose is connected to the pressure regulator.
Standard value: Approx. 264 kPa (2.7 kg/cm² , 38 psi)

Fig 5: Testing Fuel Pressure Regulator With Regulator Vacuum Hose Connected
Courtesy of KIA MOTORS AMERICA, INC.
If the results of the measurements made in steps (6) and (7) are not within the standard value, use the Illustration below to determine the probable cause, and make the necessary repairs.

Fig 6: Fuel Pressure Diagnostic Chart
Courtesy of KIA MOTORS AMERICA, INC.
Stop the engine and check for a change in the fuel pressure gauge reading, which should hold for approximately 5 minutes. If the gauge indication drops, observe the rate at which it drops. Determine and remove the causes according to the following Illustration.

Fig 7: Fuel Pressure Rest Pressure Diagnostic Chart
Courtesy of KIA MOTORS AMERICA, INC.
Reduce the pressure in the fuel line.
Disconnect the hose and the gauge.
NOTE: Cover the hose connection with a shop towel to prevent splashing of fuel caused by fuel residual pressure in the fuel line.
Connect the fuel hose to the delivery pipe and tighten.
Check for fuel leakage.
1. Apply battery voltage to the fuel pump drive terminal to operate the fuel pump.
2. With pressure, check the fuel line for leaks.