2017-2020 Kia Cadenza Fuel Pumps: Diagnosing In-Tank vs. High-Pressure Faults

Understanding the Two Fuel Pumps in Your Cadenza

Before diagnosing any issue, it's critical to understand that your 2017-2020 Kia Cadenza has two separate fuel pumps that serve different functions. Confusing the two can lead to incorrect diagnosis and unnecessary expense.

• Low-Pressure Fuel Pump (LPFP): This is the Fuel Pump Module Assembly located inside your fuel tank. It's an electric pump that sends fuel to the engine. Failures here often result in the engine not getting any fuel at all. This is the part typically sold as a complete module.
• High-Pressure Fuel Pump (HPFP): This is a smaller, mechanical pump located on the engine itself, driven by the camshaft. It takes the fuel supplied by the in-tank pump and boosts its pressure significantly for the GDI system. Failures here are common and often covered by a special warranty extension.

Symptoms of a Failing Fuel Pump

The symptoms differ depending on which pump is failing. Pay close attention to the specific OBD-II codes.

Low-Pressure (In-Tank) Fuel Pump Module Symptoms

• Engine Cranks but Won't Start: This is the most common sign. The starter turns the engine over, but it never fires up because it's not receiving fuel.
• Sudden Stalling: The engine may start and run for a moment before stalling unexpectedly as the pump fails to maintain fuel flow.
• Whining Noise from Rear Seat Area: A loud, high-pitched humming or whining sound from the fuel tank area is a classic sign of a struggling electric fuel pump motor.
• Hesitation and Power Loss: The vehicle may hesitate or sputter during acceleration as the pump can't supply enough fuel volume under load.
• Check Engine Light with Code P0087: This code means "Fuel Rail/System Pressure - Too Low." It indicates the in-tank pump isn't supplying enough fuel to the high-pressure pump, causing the entire system's pressure to drop.

High-Pressure (Engine-Mounted) Fuel Pump Symptoms

• Rough Idle and Engine Hesitation: The vehicle may run poorly, especially under load.
• Stalling When Coming to a Stop: In some cases, the engine may shut off when the vehicle is stopped but can be restarted immediately.
• Check Engine Light with Code P0088: This code means "Fuel Rail/System Pressure - Too High." This is the key indicator for the specific HPFP issue covered by Kia's warranty extension.

Known Issues, Warranty, and Recalls

High-Pressure Fuel Pump (HPFP) Warranty Extension (WTY034)

Kia has extended the warranty for the high-pressure fuel pump on 2017-2020 Cadenza models to 15 years or 180,000 miles, whichever comes first. The issue involves the fuel control valve plunger wearing unevenly and getting stuck, which triggers the P0088 code. If your vehicle exhibits symptoms of a bad HPFP and has this code, a Kia dealer should diagnose and replace the part free of charge under this program.

Technical Service Bulletin (TSB) for Fuel Pump Seal

For 2017 models, Kia issued TSB #PS567 regarding a damaged fuel pump seal. This can cause a fuel smell or trigger EVAP leak codes P0456 or P0442. This validates the importance of replacing the tank seal during any in-tank fuel pump service.

Other Recalls

While not directly related to the fuel pump module, be aware of two other safety recalls:

• Recall 18V-907 (SC172): Addresses a potential leak from the high-pressure fuel pipe connection, often after an engine replacement.
• Recall 21V-137: A fire risk from a possible short circuit in the Hydraulic Electronic Control Unit (HECU). Kia advises parking affected vehicles outdoors and away from structures until repaired.

Buying a Used In-Tank Fuel Pump Module

A used OEM fuel pump module can offer significant savings over a new part. Because these are reliable components, a low-mileage used unit is often a smart choice. Here’s what to check before buying:

• Verify Part Numbers: Ensure the part is either 31110-F6010 or 31120-F6010. These are the correct OEM numbers for the 2017-2020 Cadenza.
• Inspect the Electrical Connector: Check the pins on the main electrical connector. They should be clean, straight, and free of any corrosion or signs of burning/melting, which would indicate an electrical failure.
• Check the Plastic Housing: Look for any cracks, especially around the fuel line connections and the mounting flange. A damaged housing can cause dangerous fuel leaks.
• Confirm Mileage: Ask the seller for the mileage of the donor vehicle. A pump from a vehicle with under 100,000 miles is preferable.
• Why OEM is Better: Used OEM units are built to Kia's exact pressure and flow specifications. Some cheap aftermarket pumps can fail prematurely or cause subtle performance issues because they don't operate within the precise tolerances required by the GDI system.

Cost Comparison

The cost to replace the in-tank fuel pump module is much lower than replacing the high-pressure fuel pump. Many online estimators confuse the two, leading to inflated quotes.

Replacement Overview: In-Tank Fuel Pump Module

Replacing the in-tank fuel pump is manageable for an experienced DIYer. Access is conveniently located under the rear seat cushion.

• Difficulty: 3 out of 5. The process is straightforward, but working with fuel requires extreme caution.
• Estimated Time: 1.5 - 2.5 hours.
• Location: The pump is located in the fuel tank, with an access panel under the driver's side rear seat bottom.

Key Steps:

1. Remove the rear seat bottom cushion by pushing it toward the back of the car and pulling up.
2. Remove the black metal access panel (usually held by four screws).
3. Thoroughly clean the area around the pump to prevent dirt from falling into the tank.
4. Disconnect the electrical connector and fuel lines. Be prepared for some residual fuel to spill.
5. Unscrew the bolts holding the pump assembly to the tank. Loosen them in a star pattern to release any remaining pressure evenly.
6. Carefully lift the old assembly out of the tank, being mindful not to bend the fuel level float arm.
7. CRITICAL: Install a new fuel tank seal (Part No. 31115-C1000). Never reuse the old seal, as it can cause dangerous fuel leaks and fumes.
8. Install the new pump assembly, ensuring the float arm moves freely. Tighten the bolts to the proper torque specification, again using a star pattern.
9. Reconnect lines and the electrical connector, reinstall the access panel and seat, and reconnect the battery.

Frequently Asked Questions (FAQ)