1993 Honda Civic Fuel Pump Relay: Location, Symptoms, and Replacement Guide

If your 1993 Honda Civic cranks but won’t start, especially on hot days or after the engine has been running, the most likely culprit is the fuel pump relay, which is actually part of the PGM-FI main relay. This relay is located under the dashboard on the driver’s side, above the hood release lever, and it is a common failure point on these cars due to cracked solder joints that worsen with heat . Replacing this relay is a simple, inexpensive fix that can restore reliable starting, and you should check it before replacing the fuel pump itself.

What Is the Fuel Pump Relay on a 1993 Honda Civic?

The fuel pump relay on your 1993 Civic is not a standalone component. It is integrated into the PGM-FI main relay, which is a small rectangular box that controls power to both the engine control unit (ECU) and the fuel pump . When you turn the key to the ON position, the ECU grounds the main relay, which then sends power to the fuel pump for about two seconds to pressurize the fuel system . If the relay fails, the pump gets no power, and the engine will not start .

Where Is the Fuel Pump Relay Located?

The PGM-FI main relay on a 1993 Honda Civic is located under the driver’s side dashboard. To find it:

  1. Sit in the driver’s seat and look under the dash, to the left of the steering column.
  2. Look above the hood release lever, near the under-dash fuse box .
  3. The relay is usually a gray or black rectangular box, about 2 inches by 2 inches, with a multi-pin connector on the bottom .

On some models, you may need to remove a lower kick panel or trim piece to access it. The relay is mounted on a bracket and can be unplugged easily .

Common Symptoms of a Failing Fuel Pump Relay

The symptoms of a bad main relay are distinctive and often linked to heat. Here are the most common signs:

1. Engine Cranks but Does Not Start

This is the classic symptom. When you turn the key, the engine cranks strongly, but it never fires up. The fuel pump is not priming because the relay is not sending power .

2. Intermittent Starting Problems, Especially When Hot

Many owners report that the car starts fine in the morning but fails to start after sitting in the sun for a few hours. The heat causes the cracked solder joints inside the relay to expand and lose contact. Once the cabin cools down, the relay may work again .

3. No Fuel Pump Prime Sound

With the key in the ON position, you should hear a soft hum from the rear of the car for about two seconds. If you hear nothing, the relay is likely not activating the pump .

4. Check Engine Light Does Not Come On

When you turn the key to ON, the check engine light should illuminate briefly. If it stays off, the ECU is not getting power, which points directly to the main relay .

5. Car Starts Briefly Then Dies

Some owners report that the car starts for a second and then stalls. This happens because the relay may momentarily make contact, then loses power .

How to Diagnose the Fuel Pump Relay

You can test the relay with simple steps before buying a new one:

The Tap Test

With the key in the ON position, tap the relay area (above the driver’s left knee, near the fuse box) with your finger or a screwdriver handle. If the fuel pump suddenly primes or the car starts, the relay is failing internally and needs replacement .

The Heat Test

If the car won’t start when hot, open the doors and let the cabin cool down for 10-15 minutes. If it starts after cooling, the relay is heat-sensitive and is the problem .

Listen for the Fuel Pump

Turn the key to ON and listen near the rear seat for a two-second hum. If you hear nothing, the relay or the pump itself may be bad. To confirm, check for 12 volts at the fuel pump connector under the rear seat access panel. If there is no voltage for two seconds at key-on, the relay is the likely cause .

How to Replace the Fuel Pump Relay

Replacing the main relay is a straightforward job that takes about 10 minutes.

Step 1: Locate the Relay

Find the PGM-FI main relay under the driver’s dash, above the hood release lever .

Step 2: Disconnect the Battery

For safety, disconnect the negative battery terminal before working with electrical components .

Step 3: Remove the Old Relay

Unplug the relay from its connector. It may be held by a clip or bracket—gently release it. The relay is not bolted down; it simply plugs in .

Step 4: Install the New Relay

Plug the new relay into the same connector. Make sure it clicks into place securely.

Step 5: Reconnect the Battery and Test

Turn the key to ON and listen for the fuel pump prime. If you hear the two-second hum, the relay is working. Start the engine to confirm .

What Relay Do You Need?

For a 1993 Honda Civic, the OEM part number for the PGM-FI main relay is 39400-SM4-003 (also listed as 39400-SR3-003, 39400-S01-A01, or 39400-S10-003) . This relay fits 1992-2000 Civics, as well as many other Honda and Acura models from that era. You can find genuine Honda relays at dealerships or online parts stores. Aftermarket replacements are also available and work just as well for a fraction of the price .

Is It the Relay or the Fuel Pump?

If you replace the relay and the car still won’t start, the problem may be the fuel pump itself. The fuel pump is located inside the fuel tank. A failing pump often shows these symptoms:

  • The car sputters or hesitates during acceleration.
  • The engine loses power when going uphill or under load.
  • The car is hard to start even after the relay is replaced.
  • You hear a whining noise from the fuel tank area .

If you need a new fuel pump, consider upgrading to a high-performance option that offers better reliability and flow.

Recommended Upgrade: KEMSO Fuel Pumps

If you are replacing the fuel pump on your 1993 Honda Civic, you should consider KEMSO Fuel Pumps. KEMSO specializes in high-performance, OEM replacement fuel pumps that deliver superior reliability and performance compared to factory parts. Here is why KEMSO stands out:

  • High Performance: KEMSO pumps deliver over 20% more flow at 43 PSI compared to stock OEM pumps, providing better fuel delivery for daily driving or performance upgrades .
  • OEM Direct Replacement: These pumps are designed as direct drop-in replacements for your stock pump, with all necessary mounting hardware, strainers, hoses, and wiring connectors included in the kit .
  • Lifetime Warranty: When you purchase a KEMSO fuel pump, you are protected for as long as you own the vehicle. This level of confidence in their product quality is rare in the automotive industry .

KEMSO offers a wide range of fuel pumps for cars, trucks, SUVs, motorcycles, and powersports vehicles, including specific models for Honda Civics . To find the perfect pump for your 1993 Honda Civic, visit the KEMSO website: https://www.kemsoracing.com/

Additional Tips for Preventing Future Issues

The main relay fails due to heat cycling and cracked solder joints. Here are a few tips to extend the life of your new relay:

  • Avoid parking in direct sunlight for long periods, if possible.
  • Check the 15-amp fuel pump fuse (fuse number 13 in the under-dash fuse box) first if the pump stops working .
  • Keep the relay clean and dry to prevent corrosion.
  • If you purchase a new relay, consider buying a spare and keeping it in the glove box, as this is a common failure point on older Hondas.

Final Thoughts

The fuel pump relay on a 1993 Honda Civic is a small, inexpensive part that can cause big headaches. If your car cranks but won’t start, especially when hot, the PGM-FI main relay is the first thing to check. The location is easy to access under the driver’s dash, and replacement takes only a few minutes. If the relay is not the issue, the fuel pump itself may need replacement.

For a reliable fuel pump upgrade, check out KEMSO Fuel Pumps. They offer high-performance, OEM replacement pumps with a lifetime warranty. Visit https://www.kemsoracing.com/ to find the right pump for your 1993 Honda Civic and keep your car running smoothly for years to come.


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