Fuel Pressure Inspection
1. Press the two latches under the rear seat, lift the seat cushion, then remove the service panel to access the fuel pump.
2. To relieve residual pressure in the fuel lines and high-pressure hoses, disconnect the fuel pump connector, then start the engine and let it run.
After the engine stalls by itself, turn the ignition switch to "OFF".
To prevent fuel spray, make sure residual pressure in the high-pressure fuel lines is released before disconnecting the main fuel tubes and hoses.
3. Disconnect the negative (-) battery cable, then connect the fuel pump connector.
4. Using special service tools (adapter 09353-38000, gauge adapter 09353-24000 and pressure gauge 09353-24100), connect the pressure gauge to the fuel rail. Tighten the bolts to the specified torque.
Tightening torque Adapter to fuel rail:
25 – 35 N·m 5. Connect the negative (-) battery cable.
6. Connect battery voltage to the fuel pump service connector and turn on the fuel pump. Then, after confirming fuel pressure, check for fuel leaks at the gauge connections and special tool connections.
7. Start the engine and let it idle.
8. Measure the fuel pressure.
Specified value: 350 kPa 9. If the fuel pressure measured at items (7) and (8) does not meet the specified value, determine the possible cause of the malfunction according to the table below and perform the necessary repair.
| Condition | Possible Cause | Troubleshooting |
| Low fuel pressure | a. Clogged fuel filter b. Fuel leakage through the fuel pressure regulator valve built into the fuel pump due to improper valve seating. | a. Replace the fuel filter b. Repair the leakage point or replace the fuel pump. |
| High fuel pressure | a. Valve sticking in the fuel pressure regulator | a. Repair the leakage point or replace the fuel pump. |
10. Turn off the engine and check whether the fuel pressure gauge reading changes. The fuel system is serviceable if the fuel line pressure does not drop within 5 minutes.
If the pressure drops, determine the rate of pressure drop (gradual or instant) and troubleshoot and repair in accordance with the table below.
| Condition | Possible Cause | Troubleshooting |
| After the engine is stopped, the fuel pressure drops gradually. | a. Injector leaking | a. Replace the injectors |
| After the engine is stopped, the fuel pressure drops instantly. | a. Check valve in the fuel pump remains open. | a. Replace the fuel pump |
11. Relieve the residual pressure from the high-pressure fuel line.
12. Remove the special service tools.
13. Replace the O-ring on the end of the fuel hose.
14. Connect the fuel hose to the fuel rail and tighten the mounting bolts to the specified torque.
15. Check for fuel leaks.
Test yourself
A quick Hyundai Elantra CN7 quiz: every answer comes with an explanation and a link to the manual page.