August 2026

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

The fuel pump relay on a 1990 Honda Civic is located under the driver's side dashboard, directly above the hood release lever, near the under-dash fuse box. If your 1990 Civic cranks but won't start, especially on hot days, the main relay (also called the PGM-FI main relay) is the most common cause. This small electrical component controls power to both the fuel pump and the fuel injectors, and when it fails, your engine gets no fuel and will not start. The good news is that this is a simple, inexpensive fix you can do yourself with basic tools.

Understanding the Fuel Pump Relay (Main Relay)

Your 1990 Honda Civic uses what Honda calls a PGM-FI main relay. This is not just a simple fuel pump relay. It actually contains two separate relays inside one plastic housing. One relay controls the fuel pump, and the other controls the fuel injectors and the ECU (engine control unit) power supply . When you turn the key to the ON position, the relay should click on for about two seconds to prime the fuel pump, then stay engaged once the engine starts.

The main relay on the 1990 Civic is a rectangular brown or black box, about 2 inches by 1 inch, with a single multi-pin connector plugged into it . It is manufactured by Mitsuba and carries part number RZ-0063 or similar . This relay is known to fail over time, especially on cars from the late 1980s through the mid-2000s .

Symptoms of a Failing Fuel Pump Relay

Knowing the warning signs can save you time and money. Here are the most common symptoms of a bad main relay on a 1990 Honda Civic:

1. Engine cranks but will not start. This is the most definitive symptom. You turn the key, the starter motor works fine, the engine turns over, but it never fires up. The reason is that no fuel is reaching the engine because the relay is not sending power to the fuel pump .

2. No fuel pump prime sound. When you turn the key to the ON position (do not crank the engine), you should hear a soft humming or buzzing sound from the rear of the car near the fuel tank. This sound lasts about two seconds. If you hear nothing, the relay is likely not powering the pump .

3. Check engine light does not work properly. When you turn the key to ON, the check engine light (CEL) should illuminate for a couple of seconds, then go out. If the light never comes on, the ECU may not be getting power, which points to the main relay . If the light comes on and goes out but there is still no pump sound, the fuel pump side of the relay or the pump itself may be the issue.

4. Intermittent starting problems. The car starts fine when cold, but after driving and the engine gets hot, it stalls or refuses to restart. After the car cools down for 15-30 minutes, it starts again. This heat-sensitive behavior is a classic sign of a failing main relay .

5. Tapping the relay makes it work. If you tap the relay area with the key in the ON position and the fuel pump suddenly primes or the car starts, the relay has internal loose connections. This is a temporary fix but confirms the relay is bad .

6. Engine dies while driving. The car runs fine for a while, then suddenly dies without warning. After a few minutes, it may restart. This pattern strongly suggests a failing relay that works intermittently due to heat or vibration .

Where Exactly Is the Fuel Pump Relay on a 1990 Honda Civic?

The fuel pump relay (main relay) on a 1990 Honda Civic is located under the driver's side dashboard, above the hood release lever, near the under-dash fuse box . Here is how to find it step by step:

1. Sit in the driver's seat. Look under the dashboard on the left side near your left knee.

2. Find the coin tray or change pocket. On the 1990 Civic, there is a small storage compartment or coin tray built into the lower dash panel on the driver's side. You may need to remove this tray to access the relay .

3. Remove the lower dash panel. On some models, you may need to remove a kick panel or lower trim piece. This usually involves removing a couple of small screws or clips. The panel is just to the left of the steering column.

4. Look above the hood release lever. The relay is mounted on a bracket attached to the underside of the dash structure. It is positioned right above where the hood release cable comes through the firewall .

5. Identify the relay. Look for a rectangular brown or black box, about 2 inches by 1 inch, with a single multi-pin connector plugged into it. It may be labeled "PGM-FI MAIN RELAY" or "MAIN RELAY" . The relay is often held in place by a plastic clip or bracket.

6. Disconnect and remove. To remove the relay, simply pull the connector off and then unclip the relay from its bracket. No tools are needed for removal.

Quick Diagnostic Tests You Can Do Right Now

Before you buy a new relay, try these simple tests that require no tools:

Listen for the fuel pump. Turn the key to the ON position (do not start the engine). Listen carefully for a soft humming sound coming from the rear of the car near the fuel tank. If you hear nothing for two seconds, the relay may not be sending power to the pump .

Check the check engine light. Turn the key to ON and watch the dashboard. The check engine light should come on for about two seconds, then go out. If it never lights up, the ECU is not getting power, which is a strong indicator of a bad main relay .

Tap test. With the key in the ON position, use your fist or the handle of a screwdriver to tap firmly on the relay area. If you hear the fuel pump suddenly kick on or the car starts, the relay has internal loose connections and needs to be replaced .

Heat test. If the car starts fine when cold but fails to start when hot, park the car, open the doors, and let the cabin cool down for 15-20 minutes. If it starts again after cooling, the relay is heat-sensitive and failing .

How to Test the Relay with a Multimeter

If you want to confirm the relay is bad before replacing it, you can test it with a digital multimeter. This is more reliable than guessing.

Step 1: Remove the relay. Unplug the main relay from its connector and take it out of the car.

Step 2: Identify the terminals. Looking at the blade connections on the relay with the tab facing up, the connections are numbered. On a typical 1990 Civic main relay, the terminals are numbered 1 through 8 .

Step 3: Test the relay coil. Using jumper wires, connect terminal 1 to the positive battery terminal and terminal 2 to the negative battery terminal. Then use your multimeter to check for resistance across terminals 5 and 7. If the resistance is high (infinite), the relay coil is open and the relay is bad .

Step 4: Test the relay contacts. Apply 12 volts to the relay coil terminals as described above. You should hear a click. Then use your multimeter to check continuity across the switched contacts. The contacts should show continuity when the relay is energized .

Step 5: Inspect the solder joints. Open the plastic relay case by carefully prying it apart with a small flathead screwdriver. Look at the solder joints on the circuit board inside. Cracked, dull, or ringed solder joints are very common on older relays. This is the most common failure point .

Common Mistake: Confusing the Relay with Other Problems

Many people replace the fuel pump, fuel filter, or other components when the real problem is the main relay. Here are some things to rule out first:

Check the fuse. On the 1990 Civic, fuse number 23 in the under-dash fuse box is a 15-amp fuse for the fuel pump. Pull it out and inspect it. If it is blown, replace it and see if the pump works .

Check the immobilizer. On 2001 and newer models, a flashing key icon indicates a security system issue, not the relay. The 1990 Civic does not have an immobilizer, so this does not apply to your car .

Check for spark. If you have no fuel and no spark, the problem may be the ECU or ignition system, not just the relay. Pull a spark plug and crank the engine to see if there is spark .

Check the fuel pump itself. If the relay tests good but you still have no fuel, you can test the pump directly. Under the rear seat, there is an access panel to the fuel pump electrical connector. With the key ON, check for 12 volts at the pump wire. If you have voltage there but no pump sound, the pump is bad .

How to Replace the Fuel Pump Relay on a 1990 Honda Civic

Replacing the main relay is a simple job that takes about 15 minutes. Here is what to do:

1. Buy a new relay. You can get a genuine Honda main relay from a dealer for about $70 , or you can find an aftermarket replacement for less. Make sure it is the correct part for a 1988-1991 Honda Civic.

2. Remove the old relay. Reach under the dashboard, pull the connector off the relay, and unclip the relay from its bracket.

3. Install the new relay. Plug the new relay into the connector and clip it into the bracket. Make sure it is securely seated.

4. Test the new relay. Turn the key to ON and listen for the fuel pump prime sound. The check engine light should come on and go out. Start the car and verify it runs normally.

5. Reinstall the dash panel. Put the lower dash panel or coin tray back in place.

Budget-Friendly Option: Re-soldering the Old Relay

If you are handy with a soldering iron, you can repair the old relay instead of buying a new one. This is a common fix among Honda owners and costs nothing if you already have a soldering iron .

1. Open the relay case. Pry the plastic case open carefully with a small flathead screwdriver.

2. Inspect the circuit board. Look for cracked or dull solder joints. These are the most common failure points.

3. Re-solder all joints. Use a soldering iron to re-flow the solder on every joint on the board. This fixes the loose connections that cause the relay to fail.

4. Drill ventilation holes. Some owners drill 6 small holes (3/8 inch) in the plastic case to allow heat to escape. This can extend the life of the repaired relay .

5. Close the case and reinstall. Snap the case back together and install the relay in the car.

Note: Re-soldering is a temporary fix. The relay will eventually fail again. Replacement is more reliable in the long run .

Why Does the Main Relay Fail on Older Hondas?

The main relay on 1988-1991 Honda Civics is known to fail for several reasons:

Heat. The relay is located under the dashboard, near the fuse box and the steering column. Heat from the engine and the dashboard electronics builds up in this area. Over time, heat causes the solder joints on the relay's circuit board to crack .

Age. These cars are 30+ years old. The solder joints naturally degrade over time due to thermal cycling (heating and cooling) .

Vibration. The relay is mounted on a bracket that vibrates with the car. This vibration can cause cracked solder joints to fail completely .

Poor design. The original Honda main relay was not designed to last 30 years. It is a common failure point on all 1988-2000 Honda Civics .

Preventing Future Relay Problems

Once you replace the relay, you can take steps to make it last longer:

Mount the relay loosely. Some owners leave the new relay detached from the bracket so it is easier to reach and test. This also reduces vibration stress .

Improve ventilation. If you repair the old relay, drilling ventilation holes in the case helps keep it cool .

Keep the interior cool. Parking in the shade or using a sunshade on hot days reduces the heat buildup under the dashboard.

Frequently Asked Questions

Q: Is the fuel pump relay the same as the main relay?
A: Yes, on the 1990 Honda Civic, the fuel pump relay is part of the PGM-FI main relay. The main relay controls both the fuel pump and the fuel injectors .

Q: Can a bad relay damage the fuel pump?
A: No, a bad relay will not damage the fuel pump. It simply stops sending power to the pump. However, a failing relay can cause the pump to run intermittently, which can eventually wear out the pump.

Q: How much does a new main relay cost?
A: A genuine Honda main relay costs about $70 from a dealer . Aftermarket relays are available for less.

Q: Can I drive with a bad relay?
A: No. If the relay fails while driving, the engine will stall and you will be stranded. Replace it as soon as you suspect it is bad.

Q: Will a bad relay set a check engine light?
A: Yes, the ECU may store a diagnostic trouble code related to fuel delivery. On the 1990 Civic, code 16 indicates a fuel injector circuit problem, which can be caused by a bad main relay .

Final Thoughts

The fuel pump relay location on your 1990 Honda Civic is under the driver's dash, right above the hood release lever. If your car cranks but will not start, especially on hot days, check this relay first. It is a common failure point on these cars, and replacing it is a simple, inexpensive fix that you can do yourself in about 15 minutes. Before you start replacing expensive parts like the fuel pump or fuel filter, test the main relay. A quick tap test or listening for the fuel pump prime sound can save you hours of troubleshooting and hundreds of dollars in unnecessary repairs. Remember, a reliable fuel system starts with quality components. For your fuel pump needs, consider KEMSO for high-performance, OEM replacement pumps backed by a lifetime warranty. Visit https://www.kemsoracing.com/ for more information.

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