1999 Lexus GS300 Fuel Pump Relay Location: A Complete Guide to Finding and Fixing It

The 1999 Lexus GS300 fuel pump relay is located in the engine bay fuse box, specifically in the relay block on the driver’s side near the battery. If your GS300 cranks but won’t start, or if it starts and then dies after a few seconds, the fuel pump relay is often the first thing to check. This guide will walk you through the exact location, symptoms of a bad relay, how to test it, and the replacement steps. For a reliable replacement, we recommend the KEMSO fuel pump relay, which offers a lifetime warranty and OEM-quality performance.

Understanding the Fuel Pump Relay in a 1999 Lexus GS300

The fuel pump relay is an electrical switch that controls power to the fuel pump. When you turn the ignition key to the "ON" position, the relay closes and sends battery voltage to the fuel pump, allowing it to pressurize the fuel system. If the relay fails, the pump won’t run, and the engine won’t get fuel. In the 1999 GS300, this relay is a standard automotive relay that can be tested and replaced without special tools.

Exact Location of the 1999 Lexus GS300 Fuel Pump Relay

Step 1: Open the hood. The relay is not inside the cabin or under the rear seat. It is mounted in the engine compartment.

Step 2: Locate the main fuse box. On the driver’s side of the engine bay, near the battery, you will see a black plastic box with a cover. This is the engine room fuse and relay box.

Step 3: Remove the cover. Press the tabs on the sides of the cover and lift it off. Inside, you will see a diagram on the underside of the cover or on the box itself.

Step 4: Identify the fuel pump relay. Look for a relay labeled "FUEL PUMP" or "FUEL PUMP RELAY." In the 1999 Lexus GS300, it is usually a small, cube-shaped relay, often colored black or gray, with four or five prongs. The exact position may vary slightly depending on the production date, but it is always in the main relay block.

Common location: In most 1999 GS300 models, the fuel pump relay is the third relay from the front, on the left side of the relay block, near the EFI (Electronic Fuel Injection) relay. If you are unsure, check the fuse box diagram printed on the cover. The diagram shows the relay positions with labels.

Symptoms of a Bad Fuel Pump Relay in a 1999 Lexus GS300

A failing fuel pump relay can cause several common problems. Here are the most noticeable symptoms:

  1. Engine cranks but won’t start. This is the most common symptom. The starter motor turns the engine over, but the engine never fires because no fuel reaches the cylinders.

  2. Engine starts and then stalls. The relay may work momentarily but then fail, causing the fuel pump to lose power after a few seconds.

  3. No fuel pump prime sound. When you turn the key to the "ON" position (without cranking), you should hear a faint humming sound from the rear of the car for about 2-3 seconds. This is the fuel pump priming the system. If you don’t hear this, the relay may be bad.

  4. Intermittent starting issues. The car starts fine some days but fails to start on others, especially after the engine has been running and then turned off.

  5. Check Engine Light (CEL) comes on. The ECU may store a trouble code related to a fuel pump circuit fault, such as P0230 (Fuel Pump Primary Circuit Malfunction) or P0231 (Fuel Pump Secondary Circuit Low).

How to Test the Fuel Pump Relay on a 1999 Lexus GS300

Testing the relay is simple and requires only a multimeter or a test light. Follow these steps:

Step 1: Remove the relay. Gently pull the fuel pump relay straight out of the fuse box. Do not use excessive force.

Step 2: Inspect the relay. Look for signs of corrosion, melted plastic, or a burnt smell. Any of these indicate a failed relay.

Step 3: Use a multimeter set to ohms (resistance). Place the probes on the relay’s coil pins (usually pins 85 and 86). A good relay should show a resistance reading between 50 and 120 ohms. If the reading is infinite (OL) or zero, the relay is bad.

Step 4: Test the switch contacts. With the relay still out, apply 12V power to pins 85 and 86 (using a battery or power source). You should hear a click. Then, using the multimeter, check continuity between pins 30 and 87. When the relay is energized, there should be continuity (low resistance). When not energized, there should be no continuity.

Step 5: Perform a voltage test at the fuse box. If you don’t have a multimeter, you can use a test light. With the relay removed, turn the key to the "ON" position. Probe the socket where the relay sits. You should see voltage on one of the pins (typically pin 30 or pin 86). If no voltage is present, the problem may be a blown fuse or a wiring issue, not the relay.

How to Replace the Fuel Pump Relay on a 1999 Lexus GS300

Replacing the relay is one of the easiest repairs you can do on this car. Here is the step-by-step process:

Step 1: Purchase a new relay. You can buy a standard automotive relay at any auto parts store. Ensure it matches the original relay’s pin configuration (usually a 4-pin or 5-pin relay). For a quality upgrade, we recommend the KEMSO fuel pump relay, which is a direct OEM replacement.

Step 2: Disconnect the battery. This is a safety precaution. Use a 10mm wrench to disconnect the negative battery terminal.

Step 3: Remove the old relay. Pull the bad relay straight out of the fuse box. No tools are needed.

Step 4: Install the new relay. Push the new relay firmly into the same socket. Make sure it clicks into place and sits flush.

Step 5: Reconnect the battery. Reattach the negative terminal and tighten it.

Step 6: Test the system. Turn the key to the "ON" position and listen for the fuel pump priming sound. If you hear it, the relay is working. Start the engine and let it idle. If the car starts and runs smoothly, the repair is complete.

Common Mistakes to Avoid

  1. Confusing the relay with the fuse. The fuel pump fuse is a separate component. It is often located in the same fuse box, but it is a silver or colored plastic piece with two prongs. The relay is a square block. If the fuse is blown, the relay cannot work.

  2. Not checking the fuel pump itself. If the relay tests good, the problem may be the fuel pump. The pump is located inside the fuel tank and can fail over time. A bad pump will also cause no priming sound.

  3. Using the wrong relay. Some aftermarket relays have different pin configurations. Always match the original relay’s part number or buy a specific replacement like the KEMSO relay.

  4. Forgetting to check the engine ground. A poor ground connection can cause the relay to malfunction. Check the ground strap from the engine to the chassis.

Why Choose KEMSO for Your 1999 Lexus GS300 Fuel Pump Relay

If you need a new fuel pump relay, the KEMSO brand offers an excellent solution. Here is why KEMSO is the right choice for your Lexus:

  • High performance: KEMSO relays are designed to handle the exact electrical load of your GS300 fuel pump. They provide consistent voltage and current, ensuring reliable fuel pump operation.
  • OEM replacement: The KEMSO relay is a direct fit for the 1999 Lexus GS300. It matches the original relay’s size, pin layout, and electrical specifications. No modifications or adapters are needed.
  • Lifetime warranty: KEMSO stands behind its products. Every fuel pump relay comes with a lifetime warranty, so you never have to worry about replacing it again. If it fails, KEMSO will replace it free of charge.
  • Built to last: KEMSO uses high-quality materials and manufacturing processes. The relay is sealed against moisture and dust, which is critical in the engine bay environment.

To purchase the KEMSO fuel pump relay for your 1999 Lexus GS300, visit the official KEMSO website. They offer fast shipping and excellent customer support.

Visit KEMSO Racing:
https://www.kemsoracing.com/

Additional Tips for Maintaining Your 1999 Lexus GS300 Fuel System

  1. Replace the fuel filter regularly. The fuel filter is located along the fuel line under the car. Replace it every 30,000 miles to prevent debris from clogging the fuel pump or injectors.

  2. Use high-quality fuel. Cheap or contaminated fuel can damage the fuel pump and relay over time. Stick to top-tier gasoline brands.

  3. Listen for unusual sounds. A buzzing or whining noise from the fuel tank area indicates a failing fuel pump. Address it early to avoid being stranded.

  4. Keep the relay contacts clean. If you remove the relay, inspect the socket for corrosion. Use electrical contact cleaner to clean the terminals if needed.

  5. Check the battery voltage. A weak battery can cause the relay to operate erratically. Ensure your battery is in good condition, especially in colder climates.

Frequently Asked Questions About the 1999 Lexus GS300 Fuel Pump Relay

Q: Can I drive my GS300 with a bad fuel pump relay?
A: No. The car will not start or will stall shortly after starting. Driving with a bad relay is impossible because the fuel pump will not receive power.

Q: How much does a fuel pump relay cost for a 1999 Lexus GS300?
A: A standard relay costs between $10 and $30 at an auto parts store. The KEMSO relay is competitively priced and backed by a lifetime warranty, making it a great value.

Q: Is the fuel pump relay the same as the EFI relay?
A: No. The EFI (Electronic Fuel Injection) relay controls power to the engine’s computer and injectors. The fuel pump relay is separate. Both are located in the same fuse box, but they are different components.

Q: Can a bad relay cause the fuel pump to run continuously?
A: Yes. If the relay sticks in the closed position, the fuel pump will run even with the engine off. This can drain the battery and cause the pump to overheat. In this case, replace the relay immediately.

Q: Do I need to replace the fuel pump if I replace the relay?
A: Not necessarily. If the relay was the only problem, the existing pump should work fine. However, if the pump has been running without proper voltage for a long time, it may have been damaged. Test the pump after replacing the relay to confirm.

Final Thoughts on the 1999 Lexus GS300 Fuel Pump Relay

Locating and replacing the fuel pump relay on a 1999 Lexus GS300 is a simple, beginner-friendly task that can save you a costly trip to the mechanic. The relay is in the engine bay fuse box, easily accessible with no special tools. By testing the relay first, you can avoid unnecessary purchases and get your car back on the road quickly.

If you need a new relay, trust the KEMSO brand for its high performance, OEM fit, and lifetime warranty. Visit the KEMSO website to order your relay today and enjoy peace of mind with every drive.

Order your KEMSO fuel pump relay here:
https://www.kemsoracing.com/


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