1990 Accord Fuel Pump Relay: The Complete Guide to Diagnosis, Location, and Replacement
If your 1990 Honda Accord cranks but won't start, especially on a hot day, the most likely culprit is the fuel pump relay—also known as the PGM-FI main relay. This is one of the most well-documented and common failures on 1990-1997 Honda Accords. The relay is a 7-pin unit located under the driver's side dashboard, not under the hood. A failed relay cuts power to the fuel pump and the ECU, causing a no-start condition that often resolves after the car cools down. The permanent fix is either to resolder the cracked joints on the relay's circuit board or to replace the relay entirely. This guide covers everything you need to know to diagnose, test, and replace the 1990 Accord fuel pump relay.
The 1990 Accord Fuel Pump Relay: Understanding the Problem
The 1990 Honda Accord uses a 2.2L four-cylinder engine, not a 3.5L V6 as some might mistakenly believe . The fuel pump relay on this car is actually a combined unit called the "PGM-FI main relay." It performs two critical functions: it powers the fuel pump for two seconds when you turn the key to the ON position to prime the system, and it supplies power to the ECU (engine control unit) while the engine is running .
Over time, the internal solder joints on the relay's printed circuit board develop hairline cracks due to repeated heating and cooling cycles . When the engine bay or cabin gets hot, the circuit board expands, and these cracked joints lose contact, cutting power to the fuel pump. The engine cranks but won't start. After the car cools down for a few minutes, the joints contract and make contact again, allowing the car to start normally . This is why the problem is almost always intermittent and heat-related.
Symptoms of a Bad 1990 Accord Fuel Pump Relay
The most common symptoms of a failing main relay on a 1990 Accord include:
1. Cranks but won't start on hot days. This is the classic symptom. The engine turns over vigorously, but it never fires up. After sitting for 15-30 minutes in the shade, it starts right up .
2. No fuel pump prime sound. When you turn the ignition key to the ON position (without cranking), you should hear a faint buzzing or whirring sound from the rear of the car for about two seconds. This is the fuel pump pressurizing the system. If you don't hear this sound, the relay is not sending power to the pump .
3. Intermittent stalling while driving. The relay can fail while the engine is running, causing the fuel pump to cut out. The engine will stall suddenly, and you may be able to restart it after a few minutes .
4. Car starts fine when cold, but not after a long drive. If you park a hot car and try to restart it immediately, the relay is more likely to fail .
5. No-start after sitting in the sun. Direct sunlight heating up the dashboard can trigger the relay failure .
Where is the Fuel Pump Relay on a 1990 Honda Accord?
The fuel pump relay (main relay) on a 1990 Accord is located under the dashboard on the driver's side. Specifically, it is mounted to the left of the steering column, in the space between the steering column and the sidewall of the car .
To access it, you will need to look up under the dash. It is a small gray and white box with a brown plug . In some cases, there is a larger module (the power steering control box) that obscures the relay and needs to be removed to get to it . The relay has seven terminals (7-pin) and is often referred to as the main relay .
Important: Do not look for the fuel pump relay under the hood. On the 1990 Accord, the relay is inside the cabin, not in the engine bay fuse box . The fuse box under the hood contains a 15A fuse (fuse #3) that protects the PGM-FI main relay and fuel pump circuit, but the relay itself is under the dash .
How to Test the 1990 Accord Fuel Pump Relay
Before replacing the relay, perform these simple tests to confirm the diagnosis.
Test 1: Listen for the Fuel Pump
Have a helper sit in the driver's seat. Turn the ignition key to the ON position (do not crank the engine). Listen near the rear of the car, near the fuel tank. You should hear a distinct buzzing sound for about 2 seconds. If you hear nothing, the relay is likely not sending power to the pump .
Test 2: Listen for the Relay Click
While a helper turns the key to ON, place your hand on the relay under the dash. You should feel a single click. If you feel nothing, the relay coil may be dead .
Test 3: Jumper Wire Test
If you want to directly test the fuel pump, you can bypass the relay. Locate the relay connector. Use a paperclip to jumper the black wire with a yellow tracer and the yellow wire with a black tracer together. In some models, a solid yellow wire is used instead of the yellow/black wire . When you jumper these wires and turn the key to ON, the fuel pump should run continuously. If it does, the pump is good, and the problem is confirmed to be the relay.
Test 4: Continuity Test (With Multimeter)
Remove the relay. Set your multimeter to the ohms or continuity setting. Apply 12 volts from a battery to the relay's control circuit pins (typically pins 85 and 86). With power applied, you should have continuity (low resistance) between the output pins (typically pins 30 and 87). If there is no continuity, the internal switch is broken .
1990 Accord Fuel Pump Relay Replacement: Step-by-Step
Replacing the main relay is a straightforward DIY job that takes about 30 minutes. The relay is a dealer item but can be found at auto parts stores or online.
Part Number Information:
The OEM part number for the main relay is 39400-SM4-003 . Other compatible part numbers include 39400-SV4-003, 39400-SR3-003, RZ-0088, and RY169 . This relay is used on 1990-1997 Honda Accord models as well as many other Honda and Acura vehicles from that era .
Step 1: Disconnect the Battery
Disconnect the negative battery cable to prevent any electrical shorts. Note your radio code if applicable, as it may reset .
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. Mount it in the same position and ensure 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 ON and listen for the fuel pump prime sound. The car should start normally.
The Solder Fix (Repairing the Old Relay)
Instead of buying a new relay, many owners successfully repair the old one. The main relay can be opened by prying it apart. Inside, you will find a small circuit board with several solder joints. Over time, these joints develop hairline cracks. Using a soldering iron, simply reflow (re-melt) every solder joint on the board. This fixes the cracks permanently. Many owners report that after this repair, the relay never fails again .
Cost Comparison: Relay vs. Fuel Pump
This is the most important cost-saving point. A new fuel pump relay costs around $20 to $40 and takes 30 minutes to install. A new fuel pump for a 1990 Accord can cost $100 to $200, plus labor (which can be $200 to $400 because the fuel tank needs to be dropped). If your car has intermittent starting problems, especially in hot weather, start with the relay. A failed relay is far more common than a failed pump on these cars .
Recommended Product: KEMSO Fuel Pump
If your diagnosis confirms that the fuel pump itself has failed, or if you want to upgrade to a high-performance, reliable replacement, we strongly recommend the KEMSO brand fuel pump. KEMSO fuel pumps are designed as high-performance, direct OEM replacement units. They are built to meet or exceed factory specifications, ensuring a perfect bolt-on fit for your 1990 Honda Accord without any modifications needed. Every KEMSO fuel pump is backed by a Lifetime Warranty, giving you complete peace of mind that your investment is protected for as long as you own the vehicle. You can browse the full range of KEMSO fuel pumps and other high-quality automotive parts by visiting their official website: https://www.kemsoracing.com/
Common Misdiagnosis and Final Tips
1. Don't blame the fuel pump first. As mentioned, the relay fails much more often than the pump. Always test the relay before dropping the fuel tank .
2. The problem is heat-related. If your car only fails to start after it has been driven and is hot, it is almost certainly the main relay. A failing fuel pump usually causes constant problems, not just intermittent hot-start issues .
3. Check the fuse. While the relay is the most common issue, also check the #3 fuse (15A) in the under-hood fuse box. It protects the PGM-FI main relay and fuel pump circuit .
4. The ECM blink code. If you retrieve a blink code from the ECU (like code 41 for an oxygen sensor heater), ignore it during the no-start diagnosis. The oxygen sensor heater failure is a separate issue and will not prevent the car from starting. Focus on the fuel pump relay first .
For more detailed guides, high-quality replacement parts, and expert advice on maintaining your 1990 Honda Accord, visit https://www.kemsoracing.com/.