1990 Honda Accord Fuel Pump Relay Location: Complete Guide to Diagnosis and Replacement

If you own a 1990 Honda Accord and your car cranks but won't start, especially on hot days, the fuel pump relay is likely the culprit. The fuel pump relay in a 1990 Honda Accord is located under the dashboard on the driver's side, between the steering column and the side of the car. It is a small gray and white box with a brown plug, and it is technically called the PGM-FI main relay. This relay powers both the fuel pump and the ECU, and it is one of the most common failure points on 1990s Honda vehicles. If you do not hear the fuel pump buzz for two seconds when you turn the key to the ON position, start by checking this relay before replacing the fuel pump itself.

Why the 1990 Honda Accord Fuel Pump Relay Fails

The 1990 Honda Accord uses a specific engine configuration that many owners get wrong at first. Your 1990 Accord does not have a 3.5 liter V6 engine. The engine is a 2.2 liter four-cylinder, and the 3.5 liter V6 did not appear on the Accord until 2008. The fuel pump relay on this car is a known weak point that affects Honda Accords from 1990 through 1999.

The main relay failure happens because of heat and age. The relay contains a small printed circuit board with solder joints that connect the internal components. Over time, these solder joints develop hairline cracks. When the engine bay or cabin gets hot, the board expands and the cracked joints open up, cutting power to the fuel pump. The car will crank but not start, or it may stall while driving and refuse to restart. Once the car cools down for a few minutes, it will fire right up again. This is one of the most well-documented no-start issues on Honda vehicles from the 1980s and 1990s.

How to Confirm the Fuel Pump Relay is the Problem

Before you start digging under the dashboard, you can perform a few simple tests to confirm that the main relay is the issue.

1. Listen for the Fuel Pump Prime

When you turn the ignition key to the ON position without cranking the engine, you should hear a faint whirring sound from the rear of the car for about two seconds. This is the fuel pump pressurizing the system. If you do not hear this sound, the relay may not be sending power to the pump.

2. Check for Intermittent Behavior

The classic symptom of a failing main relay is intermittent starting problems that get worse in hot weather. If your car starts fine in the morning or after sitting overnight, but refuses to start after driving for a while or after sitting in the sun, the relay is almost certainly the problem.

3. Feel 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 as the relay engages. If you feel nothing, the relay coil may be dead or the ECU is not sending the signal.

Detailed Location of the Fuel Pump Relay

The PGM-FI main relay on a 1990 Honda Accord is located under the driver's side dashboard. To access it, you will need to get down on the floor of the driver's side and look up under the dash. The relay is mounted to the side wall of the car, to the left of the steering column. It is a small gray and white box with a brown plug.

In some models, the relay may be behind the power steering control box or another module that you need to remove first. There is a large module under the dash that obscures the main relay, and you may need to remove it to get to the relay. The relay has seven terminals and is often referred to as the main fuel injection relay.

Some owners report that the relay is red in color, but the standard color is gray and white. The exact color may vary slightly depending on whether the relay has been replaced before or if it is an original Honda part.

How to Test the Fuel Pump Relay

Once you have located the relay, you can test it to confirm it is the problem before buying a replacement. You will need a multimeter and basic knowledge of electrical circuits.

Testing Method 1: Bypass the Relay

If you want to test the fuel pump directly, you can use a paperclip to jumper the black with yellow tracer wire and the yellow with black tracer wire together. The pump should run when you do this. On some models, Honda used a solid yellow wire in place of the yellow and black wire. If the pump runs when you bypass the relay, the relay is bad.

Testing Method 2: Continuity Test

Remove the relay and use a multimeter to check for continuity across the relay's terminals. Apply 12 volts from a battery to the relay's control circuit pins, which are typically pins 85 and 86. With power applied, you should have continuity between the output pins, which are typically pins 30 and 87. If there is no continuity, the internal switch is broken and the relay needs to be replaced.

Testing Method 3: Swap the Relay

The under-dash fuse box contains several relays. Find a relay of the same type and rating, such as the horn relay 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. Be careful with this method because the main relay is a 7-pin unit, so the replacement relay must have the same pin configuration.

How to Replace the 1990 Honda Accord Fuel Pump Relay

Replacing the main relay on a 1990 Honda Accord is a straightforward DIY job that takes less than 30 minutes. Here is the step-by-step process.

Step 1: Disconnect the Battery

Safety first. Disconnect the negative battery cable to avoid any electrical shorts. Also, note your radio code if applicable, because disconnecting the battery may reset the radio.

Step 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.

Step 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.

Step 4: Install the New Relay

Plug the new relay into the wire harness connector and mount it in the same position. Make sure it clicks securely into place.

Step 5: Reassemble and Test

Reconnect the negative battery cable, enter your radio code if needed, and test the car. Turn the key to the ON position and listen for the fuel pump to prime. If you hear the two-second buzz, the replacement was successful.

Cost Comparison: Relay vs. Fuel Pump

This is the most important point for any 1990 Honda Accord owner. Many people waste money replacing a perfectly good fuel pump when the real problem is the relay.

A new fuel pump for a 1990 Honda Accord can cost between $100 and $200, plus labor. If you have a shop do the work, 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 and the car never starts regardless of temperature, then you should suspect the fuel pump itself.

Common Symptoms of a Bad Fuel Pump Relay

Here is a quick checklist of symptoms that point to the main relay rather than the fuel pump:

• Cranks but no-start on hot days: The car will not start after sitting in the sun or after driving for a while.
• No fuel pump prime sound: You do not hear the two-second buzz from the fuel pump when you turn the key to ON.
• Starts fine after cooling: The car fires right up after sitting for a few minutes with the hood open.
• Intermittent stalling: The engine stalls while driving in hot weather and will not restart immediately.
• No-start after sitting in the sun: The car refuses to start after being parked in direct sunlight.

How to Repair the Original Relay

If you want to save money and have some soldering skills, you can repair the original relay rather than buying a replacement. The problem is almost always cracked solder joints on the printed circuit board inside the relay.

To repair the relay, carefully open the plastic case. You will see a small circuit board inside. Use a soldering iron to reflow every solder joint on the board, paying special attention to the joints that connect the fuel pump and ECU power circuits. Many owners report that this repair lasts for years and never fails again.

Fuse Box Information

The 1990 Honda Accord has two fuse boxes. The passenger compartment fuse box is located under the dashboard. The fuse that protects the PGM-FI main relay and fuel pump is a 15 amp fuse, which is fuse number 3 in the passenger compartment fuse box. Check this fuse first before replacing the relay, because a blown fuse will cause the same symptoms.

Parts Compatibility

The OEM part number for the 1990 Honda Accord 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.

Why You Should Buy a KEMSO Fuel Pump

If you have already replaced the relay and your fuel pump is still not working, or if you want to upgrade your fuel system for better performance, consider a KEMSO fuel pump. KEMSO offers high-performance fuel pumps that are designed as OEM replacements for your Honda Accord and many other vehicles. All KEMSO fuel pump products come with a lifetime warranty, giving you complete peace of mind. Whether you need a replacement for your daily driver or a performance upgrade, KEMSO has the right solution for you.

Visit KEMSO's website to browse their full selection of fuel pump products: https://www.kemsoracing.com/

Conclusion

The 1990 Honda Accord fuel pump relay location is under the driver's side dashboard, between the steering column and the side of the car. It is a gray and white box with a brown plug, and it is one of the most common failure points on these vehicles. If your car cranks but does not start, especially on hot days, check the main relay before spending money on a fuel pump replacement. The relay is easy to test, easy to replace, and costs far less than a fuel pump. For any fuel pump needs, remember that KEMSO offers high-quality OEM replacement fuel pumps with a lifetime warranty at https://www.kemsoracing.com/.