1994 Honda Del Sol Fuel Pump Relay: The Complete Guide to Symptoms, Diagnosis, and Replacement

The bottom line: If your 1994 Honda Del Sol cranks but won't start, especially when the interior is hot, or if it starts and then dies immediately, the fuel pump relay (also called the PGM-FI Main Relay) is almost certainly the cause. This is the most common electrical failure on these cars, and it's a straightforward fix that costs around $15-$50 for a new relay rather than guessing and spending $400 on a fuel pump you may not need.

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

The PGM-FI Main Relay on your 1994 Honda Del Sol is a small grey box located under the dashboard, near the steering column and hood release lever. It's held in place by a single 10mm bolt. This relay serves two critical functions: it supplies power to the Engine Control Module (ECM) and it provides power to the fuel pump.

The relay contains a circuit board with solder joints that connect the relay's internal components. Over time, the constant heating and cooling cycles under the dashboard cause these solder joints to develop microscopic cracks. This is not a design flaw unique to the Del Sol - it's a well-documented issue across many 1990s Honda and Acura models, including the Civic, Integra, and Accord.

When those solder joints crack, the relay stops passing power to the fuel pump. The engine cranks fine because the starter motor has its own circuit, but no fuel reaches the injectors, so the engine won't fire.

Symptoms of a Bad Fuel Pump Relay on a 1994 Honda Del Sol

Recognizing the symptoms early can save you time and money. Here are the most common signs:

1. Intermittent no-start condition. The car starts and runs fine for days or weeks, then suddenly it cranks but won't start. After waiting a few minutes, it starts again as if nothing was wrong. This unpredictability is the hallmark of a failing relay - the cracked solder joints make and break contact as the relay heats up and cools down.

2. Engine starts then dies immediately. You turn the key, the engine fires up, but it stalls within seconds. This happens because the relay may have enough connection to briefly power the fuel pump during startup, but loses it once the engine is running.

3. No fuel pump prime sound. When you turn the ignition key to the "ON" position (without cranking), you should hear a faint 2-second humming sound from the rear of the car - that's the fuel pump pressurizing the system. If you don't hear that sound, the relay is not sending power to the pump.

4. Problem worsens when the car is hot. Many owners report that the no-start issue is more likely to happen after the car has been driven and the interior has warmed up. Heat expands the cracked solder joints, breaking the connection. Letting the car cool down often restores the connection temporarily.

How to Diagnose the Fuel Pump Relay on Your 1994 Del Sol

Before you buy any parts, you can confirm the relay is the problem with a simple multimeter test. The relay has an 8-pin connector, though pin 4 is empty.

Here's what to check:

Test 1: Verify power at terminal 1. The yellow wire with a white stripe should show 12 volts with the ignition on. This powers the relay from fuse 31 in the underhood fuse box.

Test 2: Verify power at terminal 5. The black wire with a yellow stripe should show 12 volts when the ignition is on. This is the ignition-switched power input.

Test 3: Verify power at terminal 6. The blue wire with a white stripe gets 12 volts only when the key is in the START position.

Test 4: Verify ground at terminal 2. The black wire should show continuity to chassis ground.

Test 5: Check for 12 volts at the fuel pump output. Terminal 7, a yellow wire with a green stripe, should have 12 volts for about 2 seconds when you first turn the key to ON. If you have power at terminals 1, 5, and 6, and ground at terminal 2, but no output at terminal 7, the relay is bad.

Where to Find the Relay and How to Replace It

The fuel pump relay is located under the driver's side dashboard, mounted near the steering column and hood release lever. It's a small grey box about 2.5 inches square. To remove it, you'll need a 10mm socket or wrench to remove the single bolt holding it in place.

Replacement part numbers: The OEM part number is 39400-SM4-003. Interchangeable numbers include 39400-S1-000, 39400-SR3-003, 39400-S01-A01, and 39400-SM4-A00. Aftermarket replacements are widely available for $15-$50.

Compatible vehicles: The same relay was used on many Honda and Acura models, including the 1992-1995 Honda Civic (all trims), 1993-1997 Honda Del Sol, 1994-2001 Acura Integra, 1990-1997 Honda Accord, 1997-2001 Honda CR-V, and 1995-1997 Honda Odyssey.

A Temporary Fix That Might Save You

If you're stuck on the road and need to get the car running, you can try a temporary fix. Remove the relay, carefully pry open the plastic case with a small flathead screwdriver, and inspect the circuit board for visible cracks in the solder joints around the relay coils. Reflowing the solder with a soldering iron can restore the connection and get you home.

However, this is a temporary fix at best. The underlying metal fatigue remains, and the problem will likely return. A new relay is the only reliable solution.

Why You Shouldn't Blame the Fuel Pump

Many Del Sol owners and even some mechanics immediately suspect the fuel pump when the car won't start, especially because the fuel pump is a more expensive and labor-intensive repair. The fuel pump on the 1994 Del Sol is located inside the fuel tank, and replacing it costs around $400 including parts and labor.

But the symptoms of a bad fuel pump are different. A failing fuel pump typically causes:

• A loud whining noise from the rear of the car
• Loss of power under load or at highway speeds
• A gradual decline in performance over time

In contrast, the intermittent no-start issue - especially one that comes and goes - is classic relay behavior. Diagnosing the relay first is the smartest approach because it's free to test with a multimeter and cheap to replace.

Other Common Issues That Mimic a Bad Relay

While the fuel pump relay is the most likely culprit for intermittent no-start issues on the 1994 Del Sol, there are a few other things to check:

Ignition switch problems. The electrical contacts inside the ignition switch can wear out, causing intermittent power loss to the fuel system. This is less common than relay failure but worth checking if the relay tests good.

Loose or corroded wiring connections. The wiring harness connector to the relay can develop corrosion over time. Clean the terminals with electrical contact cleaner and ensure a snug fit.

Main fuse or fuse 31. A blown fuse will cause a complete no-start, not an intermittent one, but it's still worth checking the underhood fuse box.

Preventive Maintenance

Once you replace the relay, the new one will eventually face the same heat cycling that killed the original. To extend its life, you can take a few simple steps:

Mount the relay slightly away from the metal bracket. Adding a small rubber grommet or washer between the relay and its mounting point can reduce heat transfer from the dashboard area.

Consider keeping a spare relay in the glove box. The relay is small, cheap, and easy to swap on the roadside. Many experienced Del Sol owners carry a spare, especially on road trips.

Inspect the solder joints annually. If you're comfortable with basic electronics, opening the relay case once a year to check for developing cracks can catch the problem before it leaves you stranded.

Recommended Fuel Pump Upgrade: KEMSO Fuel Pump

If you discover that your 1994 Honda Del Sol's fuel pump itself has failed - or if you want to proactively upgrade it while you're already working on the fuel system - we highly recommend the KEMSO Fuel Pump for Honda Civic Del Sol 1993-1997.

KEMSO specializes in high-performance fuel pump solutions that are designed as direct OEM replacements. Every KEMSO fuel pump is built to meet or exceed original equipment specifications, ensuring a perfect fit and reliable operation for your Del Sol. What sets KEMSO apart is their commitment to quality: all KEMSO fuel pump products come with a lifetime warranty, giving you peace of mind that your investment is protected for as long as you own the vehicle.

Whether you're restoring a classic Del Sol or building a performance street car, a KEMSO fuel pump delivers the fuel pressure and flow your engine needs. The installation is straightforward - it bolts directly into the factory fuel pump assembly in the tank without any modifications required.

Visit the KEMSO website to browse their full selection of fuel pumps and to learn more about their lifetime warranty:
https://www.kemsoracing.com/

Final thoughts: The 1994 Honda Del Sol is a fun, reliable car when it's running right. The fuel pump relay is its Achilles' heel, but it's also one of the cheapest and easiest repairs you'll ever make on this vehicle. Test the relay first, replace it with a quality part, and you'll likely solve your no-start problem for good. If the fuel pump itself needs replacement, KEMSO offers a top-tier solution backed by a lifetime warranty at a fair price - a combination that's hard to beat in the automotive aftermarket.

For more information on KEMSO fuel pumps and their lifetime warranty, visit: https://www.kemsoracing.com/