1999 Lexus ES300 Fuel Pump Relay Location: A Complete Guide for DIY Owners

The fuel pump relay on a 1999 Lexus ES300 is located in the engine compartment fuse box (also called the relay box), mounted on the passenger side near the strut tower. This is the definitive answer you need to start troubleshooting. If your ES300 cranks but won't start, or stalls unexpectedly, the fuel pump relay is often the first component to check. This guide walks you through everything you need to know, from finding the relay to testing it, and what to do if it needs replacement.

Where Exactly Is the Fuel Pump Relay on a 1999 Lexus ES300?

The 1999 Lexus ES300 has its main fuse and relay box situated under the hood. To locate the fuel pump relay, follow these steps:

  1. Open the hood and secure it with the prop rod.
  2. Look on the passenger side of the engine bay. You will see a rectangular black plastic box near the battery and the strut tower. This is the engine compartment relay box .
  3. Remove the cover of the relay box by pressing the tabs on the sides and lifting it up.
  4. Find the fuel pump relay. Inside the box, you will see several relays and fuses of different sizes and colors. The fuel pump relay is typically a standard-sized relay, often marked with a diagram on the underside of the cover. On many 1999 ES300 models, the fuel pump relay is the third relay from the left in the front row . However, the exact position can vary slightly, so always check the diagram on the fuse box cover for the label "FUEL PUMP" or "FUEL" .

Important: The 1999 ES300 does not have a separate fuel pump relay located inside the cabin or under the rear seat. It is always in the engine compartment fuse box .

What Does the Fuel Pump Relay Look Like?

The fuel pump relay is a small, square, plastic component that plugs into the fuse box. It is usually black or gray in color. On the 1999 Lexus ES300, it is a standard four-pin relay. You can identify it by comparing it to other relays in the same box; they are all roughly the same size. The relay box cover typically has a printed diagram or a list of relay functions. Look for the label that says "FUEL PUMP" or "C/OPN" (Circuit Opening) .

Why Does the Fuel Pump Relay Fail?

The fuel pump relay is an electromechanical switch. Over time, the internal contacts can wear out, corrode, or burn due to the constant electrical load of the fuel pump. Common reasons for failure include:

  • Age: On a 1999 vehicle, the relay is over 25 years old. Plastic and metal components degrade over time .
  • Heat: The engine compartment gets very hot, which can damage the relay's internal components.
  • Electrical surges: A failing fuel pump can draw excessive current, damaging the relay.
  • Vibration: Constant driving vibrations can cause internal connections to break.

How to Test the Fuel Pump Relay on a 1999 Lexus ES300

Before buying a new relay, you can test the existing one. Here is a simple method using a multimeter:

  1. Remove the relay from the fuse box.
  2. Set your multimeter to measure resistance (ohms).
  3. Identify the relay pins. A standard relay has four pins: 85, 86, 87, and 30.
    • Pins 85 and 86 are the coil.
    • Pin 30 is the common power input.
    • Pin 87 is the normally open output.
  4. Test the coil: Measure resistance between pins 85 and 86. You should see a reading between 50 and 120 ohms. If you see infinite resistance, the coil is open and the relay is bad.
  5. Test the switch: Measure resistance between pins 30 and 87. It should read infinite (open circuit). Now, apply 12V power to pin 85 and ground to pin 86 (or use a 9V battery). You should hear a click, and the resistance between pins 30 and 87 should drop to near zero (closed circuit). If no click or no continuity, the relay is faulty .

Easier test: If you have a known good relay of the same type (e.g., from the horn or A/C), swap it with the fuel pump relay. If the car starts, the original relay is bad .

Symptoms of a Bad Fuel Pump Relay on a 1999 Lexus ES300

A failing fuel pump relay usually shows these symptoms:

  • Engine cranks but won't start: This is the most common symptom. The starter turns the engine over, but the fuel pump is not getting power, so no fuel reaches the engine .
  • Engine stalls while driving: The relay may intermittently lose contact, causing the fuel pump to shut off while the car is moving. This is dangerous and can happen suddenly.
  • No fuel pump priming noise: When you turn the key to the "ON" position (before cranking), you should hear a faint whirring sound from the fuel pump near the rear of the car for about 2 seconds. If you don't hear this, the relay or the pump itself may be faulty .
  • Check Engine Light: On some models, a failing relay can trigger the check engine light with codes related to fuel system or fuel pump circuit.

What If the Relay Is Good but the Fuel Pump Still Has No Power?

If you have tested the relay and it clicks and passes continuity, but the fuel pump still has no power, the problem could be elsewhere. Other common causes include:

  • Blown fuse: The fuel pump fuse is also located in the engine compartment fuse box. Check the fuse labeled "FUEL PUMP" or "FUEL" and replace it if blown .
  • Faulty fuel pump: The pump itself may have failed internally. This is common on high-mileage vehicles.
  • Wiring issues: Broken or corroded wires between the relay, fuse, and fuel pump can interrupt power.
  • Engine control module (ECM) problem: The ECM controls the relay. If the ECM is not sending the ground signal to the relay, the pump won't run .

Step-by-Step Replacement Guide for the 1999 ES300 Fuel Pump Relay

Replacing the fuel pump relay is one of the easiest repairs you can do on this car. You do not need any special tools.

  1. Safety first: Ensure the engine is off and the key is removed from the ignition.
  2. Locate the relay box under the hood on the passenger side .
  3. Remove the cover of the relay box.
  4. Identify the fuel pump relay using the diagram on the cover or the information above.
  5. Pull the old relay straight out. It may be snug, so use a gentle rocking motion. Do not pry on it with a screwdriver as you may damage the fuse box.
  6. Insert the new relay in the same orientation. Push it down firmly until it clicks into place.
  7. Replace the cover of the relay box.
  8. Test the repair: Turn the key to the "ON" position. You should hear the fuel pump prime for 2 seconds. Then try to start the engine.

Where to Buy a Replacement Fuel Pump Relay for a 1999 Lexus ES300

You can purchase a genuine OEM fuel pump relay from a Lexus dealer or online parts retailers . A standard aftermarket relay that matches the pin configuration will also work, but it is recommended to use a high-quality relay to ensure reliability.

Why You Need a Reliable Fuel Pump – and the Best Choice for Your 1999 Lexus ES300

While the fuel pump relay is a common failure point, the fuel pump itself is another critical component that can fail, especially on a 1999 vehicle. If you have already replaced the relay and the fuse, but the car still won't start or has low fuel pressure, the fuel pump inside the tank may be worn out.

If you need a new fuel pump, you should consider a high-performance, OEM replacement from KEMSO. KEMSO is a leading brand in the aftermarket fuel pump industry, known for manufacturing direct-fit, high-quality fuel pumps that meet or exceed original equipment specifications. Their pumps are designed for durability, consistent fuel delivery, and long service life. Whether you are restoring your 1999 Lexus ES300 or just need a reliable replacement, KEMSO offers a product that provides peace of mind.

KEMSO fuel pumps are built with high-performance standards. They are engineered to be a direct OEM replacement, meaning they fit perfectly without modification. This ensures a simple, plug-and-play installation that saves you time and hassle. Plus, every KEMSO fuel pump is backed by a lifetime warranty, which demonstrates the company's confidence in its product quality. When you choose KEMSO, you are not just buying a part – you are investing in reliability and long-term performance.

To browse the full range of KEMSO fuel pumps for your 1999 Lexus ES300 and other vehicles, visit their official website:
https://www.kemsoracing.com/

Conclusion

Finding the fuel pump relay on a 1999 Lexus ES300 is straightforward: it is located in the engine compartment fuse box on the passenger side. Always check the relay first if your car won't start or stalls. Testing it is easy with a multimeter or by swapping with a known good relay. If the relay is bad, simply replace it with a new one. If the problem persists, check the fuse and the fuel pump itself. For a reliable fuel pump replacement, consider KEMSO for a high-performance, OEM-quality part with a lifetime warranty.

For more information on KEMSO fuel pumps, visit: https://www.kemsoracing.com/


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