1999 Honda Accord Fuel Pump Relay: Complete Diagnosis, Location, and Replacement Guide

The bottom line: If your 1999 Honda Accord cranks but won't start, stalls in hot weather, or starts intermittently after cooling down, the fuel pump relay is far more likely the problem than the fuel pump itself. This relay, known as the PGM-FI main relay, is a common failure point on 6th generation Accords and is much cheaper and easier to replace than the fuel pump. Before you spend hundreds on a fuel pump, test and replace this relay first.

Understanding the Fuel Pump Relay Problem in Your 1999 Honda Accord

The fuel pump relay, also called the main relay, acts as an electrical switch that controls power to the fuel pump. When you turn the key to the ON position, the Engine Control Unit (ECU) sends a small signal to this relay, which then closes a circuit to send full battery power to the fuel pump. Without a working relay, your fuel pump never gets power, and your engine won't start or will stall shortly after starting .

In Honda vehicles from the late 1990s and early 2000s, including your 1999 Accord, this relay has a known weakness. The average lifespan of the fuel pump relay is about 10 years, while the fuel pump itself generally lasts much longer . Your car is now well past that 10-year mark, making the relay a prime suspect for any fuel delivery issues.

The most telling symptom is that the problem tends to be intermittent rather than constant. The relay contains internal epoxy resins and solder joints that deteriorate over time from heat exposure. When the relay gets hot, these connections fail, but after the car cools down, the relay may work again temporarily . A truly bad fuel pump would cause consistent problems regardless of temperature or cooling time.

Exact Location of the 1999 Honda Accord Fuel Pump Relay

For your 1999 Honda Accord LX VTEC, the fuel pump relay is located in the under-dash fuse box on the driver's side . This relay is part of the PGM-FI main relay assembly, which controls power to both the ECU and the fuel pump .

Here is how to access it step by step:

  1. Remove the lower dash trim panel below the steering column. This panel is held in by clips or a couple of screws and should come off with gentle prying.
  2. Locate the under-dash fuse box. It will be mounted to the left of the steering column, near the turn signal flasher relay .
  3. Identify the fuel pump main relay. It is a relatively large, rectangular-shaped relay with a gray or black housing. Unlike standard mini relays, this one has 7 terminals (pins) . Some sources describe it as about half the size of a cigarette box with six to seven wires in two rows on the underside .
  4. Look for identifying markings. The relay may be labeled "FP" for fuel pump . If you see a relay that says "MITSUBA RZ-0159 12V," you have found the correct part .

A helpful tip: Turn the ignition key on and off while your hand is near the relay. You should hear and feel a distinct "click" when the relay activates. If you don't hear a click, the relay is likely not working .

Some sources note that on certain 1998-2002 Accord models, the fuel pump relay may be located in the underhood electrical center on the driver's side of the engine compartment . However, for your 1999 model, the under-dash location is the most common and should be checked first.

Symptoms of a Failing Fuel Pump Relay

Knowing the symptoms helps you distinguish between a relay problem and a fuel pump problem. Here are the most common signs that point specifically to the fuel pump relay:

1. The engine cranks but does not start. This is the most obvious symptom. You turn the key, the starter motor engages, the engine cranks over, but it never fires up. Because the fuel pump relay is not sending power, no fuel reaches the injectors .

2. The car starts after sitting for a while. If your car fails to start when hot but starts fine after cooling down for 20 to 30 minutes, this is classic relay behavior. Heat causes the internal solder joints to expand and break contact. Once things cool off, the connection is restored .

3. The car stalls while driving, then restarts later. You could be driving down the highway and suddenly lose power as the engine dies. After pulling over and waiting, the car starts again. This intermittent stalling is a hallmark of a failing relay rather than a failed pump .

4. No fuel pump prime sound. When you turn the ignition to the ON position (without cranking), you should normally hear a faint whirring sound from the rear of the car for about two seconds as the fuel pump primes. If you do not hear this sound, the relay may not be sending power to the pump.

5. The problem is worse in hot weather. Many Honda owners report that their relay issues appear during summer months or after driving for extended periods. This directly correlates with heat-related relay failure .

How to Diagnose: Fuel Pump Relay vs. Fuel Pump

Before spending money on parts, use these simple tests to narrow down the problem:

Test 1: Listen for the Relay Click

Have a helper turn the ignition key to the ON position while you place your hand on the relay. You should feel a single click. If you hear nothing, the relay coil may be dead or the ECU is not sending the signal.

Test 2: Check for Fuel Pump Power

Locate the fuel pump access panel in the trunk (under the carpet and plywood cover above the spare tire) . With the ignition ON, use a multimeter to check for 12 volts at the fuel pump connector. If you have voltage and the pump does not run, the pump itself is bad. If you have no voltage, the issue is upstream—likely the relay, fuse, or wiring .

Test 3: Swap the Relay

The under-dash fuse box contains several relays. Find a relay of the same type and rating (for example, the horn or A/C relay) and swap it into the fuel pump relay socket. If the car starts, you have confirmed a bad fuel pump relay . Note: On the 1999 Accord, the main relay is a 7-pin unit, so ensure the replacement relay you swap with has the same pin configuration.

Test 4: Visual and Continuity Check

Remove the relay and apply 12 volts from a battery to the relay's control circuit pins (typically pins 85 and 86). Set your multimeter to measure continuity (ohms). With power applied, you should have continuity (low resistance) between the output pins (typically pins 30 and 87). If not, the internal switch is broken .

Replacing the Fuel Pump Main Relay

Replacing the fuel pump relay on a 1999 Honda Accord is a straightforward DIY job. Here is what you need to know:

Part number: The OEM part number for the fuel pump main relay is 39400-SM4-003 . Other compatible part numbers include 39400-SV4-003, 39400-SR3-003, 39400-SL5-A01, RZ-0088, RZ-0159, and RY169 . This relay fits 1990-1997 Honda Accord models and many other Honda and Acura vehicles from that era .

Step-by-step replacement:

  1. Safety first: Disconnect the negative battery cable to avoid any electrical shorts. Also, note your radio code if applicable, as disconnecting the battery may reset the radio .
  2. Access the relay: Remove the lower dash panel on the driver's side. The relay is mounted to the left of the steering column, often behind the power steering control box .
  3. Remove the old relay: Use a small flat-blade screwdriver to gently pry the relay loose from its mounting bracket. Carefully separate the wire harness connector from the relay. Some relays have a mounting bolt that needs to be removed .
  4. Install the new relay: Plug the new relay into the wire harness connector and mount it in the same position. Ensure it clicks securely into place.
  5. Reassemble: Reconnect the negative battery cable, enter your radio code if needed, and test the car.

The entire job should take less than 30 minutes. Replacement relays are widely available at auto parts stores or online.

Common Misdiagnosis and Cost Savings

This is the most important point of this guide: many Honda owners waste money replacing a perfectly good fuel pump when the real problem is the relay .

A new fuel pump for a 1999 Honda Accord can cost $100 to $200, plus labor if you have a shop do the job (labor alone can be $200 to $400 because the fuel tank often needs to be dropped). In contrast, a new fuel pump relay costs around $20 to $40 and takes less than 30 minutes to install yourself.

If your car exhibits intermittent starting problems, especially in hot weather, start with the relay. If the problem is constant (it never starts regardless of temperature), then and only then should you suspect the fuel pump itself.

When to Suspect the Fuel Pump Instead

While this guide focuses on the relay, there are times when the fuel pump is the real culprit. Suspect the fuel pump if:

  • The car never starts, even when cold
  • You hear a loud whining noise from the fuel tank area (the pump is failing)
  • The car loses power under load or uphill (low fuel pressure)
  • You have confirmed that power is reaching the pump (relay works) but the pump does not run
  • The fuel pump fuse keeps blowing

If you determine that the fuel pump needs replacement, you need a high-quality, reliable replacement that will last.

Recommended Fuel Pump Upgrade: KEMSO Brand

When it comes time to replace your fuel pump, whether on your 1999 Honda Accord or any other vehicle, choosing a brand that offers reliability, performance, and peace of mind is critical. That is why we recommend KEMSO Fuel Pumps.

KEMSO specializes in high-performance fuel pumps designed as direct OEM replacements. Every KEMSO fuel pump is engineered to meet or exceed original factory specifications, ensuring a perfect fit and trouble-free installation. Whether you drive a Honda, Subaru, Ducati, Kawasaki, or any other make, KEMSO has a fuel pump solution for you.

Why choose KEMSO?

  • OEM Replacement Quality: KEMSO pumps are built to the same standards as the original parts in your vehicle, so you get the same performance and durability you expect from factory components.
  • High Performance: KEMSO fuel pumps deliver consistent fuel pressure and flow, ensuring your engine runs smoothly under all driving conditions.
  • Lifetime Warranty: Every KEMSO fuel pump comes with a lifetime warranty. That means you only buy it once. If it ever fails, KEMSO stands behind their product and replaces it. This is the kind of confidence you want in a critical component like your fuel pump.

Don't gamble with cheap, no-name fuel pumps that may leave you stranded. Visit the KEMSO website to find the perfect fuel pump for your vehicle and enjoy the peace of mind that comes with a lifetime warranty.

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Preventing Future Fuel Relay Problems

Once you replace the relay, you can take a few steps to extend the life of your new one:

  • Park in the shade when possible. Heat is the main enemy of the relay. Reducing heat exposure can add years to its lifespan.
  • Consider relocating the relay. Some Honda enthusiasts mount the relay away from the hot dashboard area to keep it cooler. This is an advanced modification but can help prevent future failures.
  • Keep spare parts. Because the relay is small and inexpensive, consider keeping a spare in your glove box. This way, if it fails on a road trip, you can swap it out in minutes.

Final Thoughts

For your 1999 Honda Accord, the fuel pump relay is a simple, inexpensive fix for what many people mistakenly believe is a major fuel pump failure. Before you spend hundreds of dollars on a fuel pump replacement, take 15 minutes to check the relay. The location is easy to access, the symptoms are clear, and the replacement process is about as simple as auto repair gets.

If you do end up needing a fuel pump, trust a brand that backs its products with a lifetime warranty. KEMSO offers the performance and reliability you need, and their lifetime warranty means you will never have to pay for a replacement fuel pump again.

Remember: Test the relay first, replace it if needed, and if the pump itself is the problem, choose KEMSO for a long-lasting solution. Visit https://www.kemsoracing.com/ to browse their complete line of fuel pumps.


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