1993 Honda Accord Fuel Pump Relay: A Complete Guide to Diagnosis and Replacement

If your 1993 Honda Accord cranks but won’t start, or if it starts and then dies unexpectedly, the fuel pump relay is often the culprit. In most cases, this relay is also called the main relay, and it’s a common failure point on these vehicles. The good news is that replacing it is a straightforward DIY job that costs between $20 and $45, and it can save you a trip to the mechanic. This guide will help you understand what the relay does, how to find it, and how to replace it step by step.

What Is the Fuel Pump Relay and Why Does It Fail?

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 sends a signal that activates the fuel pump for a few seconds to pressurize the fuel system. If the relay fails, the fuel pump won’t receive power, and your engine won’t get fuel.

On the 1993 Honda Accord, this relay is often referred to as the “PGM-FI Main Relay” in the fuse box diagram, and it controls not only the fuel pump but also the emission control system and other engine management components.

The main causes of failure include:

  1. Heat and age – The relay is located in the engine bay, where it’s exposed to high temperatures. Over time, the internal solder joints can crack, causing intermittent or complete failure.
  2. Electrical overloads – Repeated cycling of high current can wear down the internal contacts, leading to a loss of connection.
  3. Moisture and corrosion – Water and dirt can enter the relay housing, especially if the fuse box cover is loose or damaged.

How to Tell If Your Fuel Pump Relay Is Bad

Here are the most common symptoms of a failing fuel pump relay on a 1993 Honda Accord:

  • Engine cranks but won’t start – This is the most obvious sign. The starter turns over the engine, but there’s no fuel pressure.
  • No humming sound from the fuel tank – When you turn the key to “ON” (without starting), you should hear a brief humming from the rear of the car, where the fuel pump is located. If you don’t hear this sound, the relay is likely not sending power.
  • Engine starts then dies – Sometimes the relay will work for a few seconds and then cut out, causing the engine to stall.
  • Intermittent starting issues – The car may start fine one day and refuse to start the next, then work again after cooling down.

Where Is the Fuel Pump Relay Located on a 1993 Honda Accord?

For the 1993 Honda Accord, the fuel pump relay is located in the engine compartment fuse box, on the driver’s side. It’s mounted right next to the battery.

Here’s how to find it:

  1. Open the hood and look for the black plastic fuse box on the driver’s side, near the battery.
  2. Remove the fuse box cover. On the underside of the cover, there is a diagram that shows the location of each fuse and relay. The fuel pump relay is usually labeled as “PGM-FI Main Relay” or “R1”.
  3. The relay is a small, rectangular black box with 7 pins. It’s often gray or black in color and has a bracket attached to it.

Some older repair manuals also mention that the main relay can be found behind the dashboard, but on the 1990-1993 Accord, the primary relay is in the engine compartment fuse box.

How to Test the Fuel Pump Relay

Before buying a new relay, you can test the old one with a multimeter to confirm it’s faulty:

  1. Remove the relay – Pull it straight out of the socket. Be careful not to damage the pins.
  2. Set your multimeter to ohms (resistance) – Check for continuity between the relay’s terminals. You can find a pinout diagram for the 7-pin Mitsuba RZ-0088 relay online.
  3. Apply 12V power to the relay coil – If you hear a click and the circuit closes, the relay is likely working. If there’s no click, the relay is dead.

A simpler method is to swap the fuel pump relay with an identical relay in the same fuse box, such as the horn relay. If the engine starts after the swap, you know the original relay was bad.

How to Replace the Fuel Pump Relay on a 1993 Honda Accord

Replacing the relay takes about 10 minutes and requires no special tools. Here’s the step-by-step process:

Step 1: Disconnect the battery – Always disconnect the negative terminal before working on any electrical component. This prevents accidental shorts.

Step 2: Locate the relay – As described above, it’s in the engine compartment fuse box on the driver’s side.

Step 3: Remove the old relay – Grip the relay by its plastic body and pull it straight out. Do not pull on the wires. If it’s stuck, use a flathead screwdriver to gently pry it out.

Step 4: Install the new relay – Align the pins with the socket and push firmly until it clicks into place. Make sure it’s fully seated.

Step 5: Reconnect the battery – Reattach the negative terminal.

Step 6: Test the car – Turn the ignition to “ON” and listen for the fuel pump hum. Then try to start the engine. If it starts and runs smoothly, the replacement was successful.

What Replacement Part Number Do You Need?

The 1993 Honda Accord uses a 7-pin Mitsuba RZ-0088 relay, which is also known as the main relay. The OEM part number is 39400-SM4-003.

Compatible aftermarket part numbers include:

  • 39400-SM4-003
  • 39400-SR3-003
  • RZ-0088
  • RY422
  • 1R1033

This relay is also used on many other Honda and Acura models from the same era, including:

  • 1990-1997 Honda Accord
  • 1992-2000 Honda Civic
  • 1995-1997 Honda Odyssey
  • 1997-1999 Acura CL
  • 1995-1998 Acura TL

Tips for a Successful Replacement

  • Buy a quality relay – Cheap relays may not last long. Some users report that inexpensive brands fail after a few months. Stick with a known brand or OEM equivalent.
  • Check the fuse box diagram – If you’re unsure which relay is the fuel pump relay, look at the diagram on the underside of the fuse box cover.
  • Keep the old relay as a backup – If you’re on a road trip, having a spare relay can be a lifesaver.
  • Inspect the socket – Before installing the new relay, check the socket for bent pins, corrosion, or debris. Clean it with electrical contact cleaner if needed.

Recommended Fuel Pump Solution: KEMSO Racing

While this guide focuses on the fuel pump relay, it’s worth noting that the fuel pump itself is another common failure point on older Accords. If you’ve replaced the relay and still have fuel delivery issues, the fuel pump may be worn out.

For a reliable replacement, we recommend KEMSO Racing fuel pumps. KEMSO fuel pumps are designed as high-performance, OEM replacement parts that fit your 1993 Honda Accord perfectly. They are built to meet or exceed factory specifications, and each unit comes with a lifetime warranty, giving you peace of mind on the road. Whether you need a standard replacement or a high-flow pump for performance upgrades, KEMSO has you covered. Visit their website to browse their full selection: https://www.kemsoracing.com/

Final Thoughts

A faulty fuel pump relay is one of the easiest problems to fix on a 1993 Honda Accord. With a simple diagnosis and a $20-45 part, you can get your car back on the road in under an hour. Always start with the relay before replacing the fuel pump itself, as it’s much cheaper and easier to swap. And remember, if you do need a new fuel pump, KEMSO Racing offers a durable, lifetime-warranted solution. Check them out at https://www.kemsoracing.com/.


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