2005 Volvo S40 Fuel Pump Relay: Complete Location Guide and Troubleshooting Steps

The bottom line: The fuel pump relay on a 2005 Volvo S40 is located inside the passenger compartment fuse box, which sits under the glove box on the passenger side. It is fuse position F38 (rated at 15A), and the relay itself is labeled as the "Fuel pump relay" in the relay block above the fuses. If your engine cranks but won't start, or if the fuel pump stays silent when you turn the key, this relay is the first thing to check.

This guide walks you through everything you need to know about the 2005 S40 fuel pump relay—where it lives, how to test it, how to replace it, and what to do if the relay isn't the problem. We will keep things practical and direct, so you can get back on the road without unnecessary guesswork.

Understanding What the Fuel Pump Relay Does

The fuel pump relay is a small electrical switch that controls power delivery to the fuel pump. When you turn the ignition key to the "ON" position, the relay closes and sends battery voltage to the fuel pump, which then pressurizes the fuel system. The pump should run for a couple of seconds and then stop if the engine doesn't start. If the relay fails, the pump never receives power, and the engine will crank indefinitely without firing up.

A failing relay often shows these warning signs:

  • Engine cranks but does not start
  • No fuel pump hum when the ignition is turned on
  • Intermittent starting issues (the car starts fine one day, then refuses the next)
  • Engine stalls while driving, then restarts after a while

These symptoms can also point to a bad fuel pump, a clogged fuel filter, or a wiring fault, so proper diagnosis matters before you buy any parts.

Where the Fuel Pump Relay Is Located

On the 2005 Volvo S40, the fuel pump relay is not in the engine bay. It is inside the car, in the main fuse and relay box under the passenger-side glove compartment. This is the same box that houses most of the cabin fuses and the fuel pump relay.

How to Access the Fuse Box

Follow these three steps to get to the relay:

  1. Remove the trim panel. Look under the glove box for a fabric or plastic lining. There are two retaining clips with center pins. Press the center pin in about one centimeter, then pull the entire clip out. Do this for both clips and lower the trim.
  2. Loosen the two wing screws. You will see two small screws holding the fuse box itself. Turn them counterclockwise until they release.
  3. Lower the fuse box. Pull the box halfway out. You now have access to both the fuses and the relay block on the top of the box.

Where to Look Inside the Box

Once the fuse box is lowered, look at the relay block mounted on the top edge of the fuse box. The fuel pump relay is clearly marked in the diagram printed on the inside of the cover. It is one of five relays in the block, located in the first position (slot 1). The other relays are for ignition circuits and are labeled accordingly.

The fuse that protects the fuel pump circuit is F38, a 15-amp fuse. If the relay is fine but the pump still doesn't run, check this fuse first. It sits in the lower section of the same fuse box.

How to Test the Fuel Pump Relay

Before you spend money on a new relay, spend ten minutes testing the one you have. You will need a multimeter and, ideally, a second relay known to be good.

Step 1: Listen for the Pump

Turn the ignition key to the "ON" position (do not crank the engine). You should hear a faint hum from the rear of the car for about two seconds. That is the fuel pump priming. If you hear nothing, proceed to the next step.

Step 2: Check for Voltage at the Relay

With the ignition still in the "ON" position, use a multimeter to check for 12 volts at relay terminal 30 (the power input terminal). If there is no voltage, check fuse F38 and the wiring leading to the relay. If voltage is present, move on.

Step 3: Test the Relay Coil

Remove the relay from its socket. Set your multimeter to measure resistance (ohms). Place the probes on terminals 85 and 86 (the coil terminals). A good relay will show a resistance reading typical for its coil—usually between 50 and 120 ohms, though this varies by manufacturer. If you get an open circuit (infinite resistance), the coil is burned out and the relay needs replacement.

Step 4: Check the Switch Contacts

With the relay removed, place the multimeter probes on terminals 30 and 87. You should read infinite resistance (open circuit) when the relay is at rest. Now apply 12 volts to terminal 85 and ground terminal 86. You should hear a click, and the multimeter should now show near-zero resistance (closed circuit). If not, the relay contacts are worn out.

Step 5: Swap with a Known Good Relay

The quickest test is to swap the fuel pump relay with another identical relay from the same block. If the car starts, the old relay is bad. Just make sure the relay you borrow controls a non-critical circuit, or simply buy a replacement and test with that.

How to Replace the Fuel Pump Relay

Replacing the relay is a simple job. Here is the step-by-step process:

  1. Ensure the ignition is off and the key is removed from the ignition switch.
  2. Lower the passenger-side fuse box following the steps described earlier.
  3. Identify the fuel pump relay in the relay block (first position, labeled "Fuel pump relay").
  4. Gently pull the relay straight out of its socket. Do not twist or pry. Use a relay puller if you have one.
  5. Compare the old relay with the new one to confirm the part number and pin layout are identical.
  6. Press the new relay firmly into the socket until it clicks into place.
  7. Reinstall the fuse box, tighten the two wing screws, and reattach the trim panel.
  8. Test the system by turning the ignition to "ON" and listening for the fuel pump prime.

The entire job should take less than fifteen minutes.

What If the Relay Is Good but the Pump Still Doesn't Run?

If the relay tests fine and you still have no fuel pressure, the problem may lie elsewhere. Here is a quick checklist:

  • Check fuse F38 again. A blown fuse is common and easy to miss.
  • Check for power at the fuel pump connector. The pump is located in the fuel tank. On the 2005 S40, there is an access panel under the rear seat cushion. You can unplug the pump harness and test for voltage with the ignition in the "ON" position.
  • Listen for the pump directly. Have a helper turn the ignition on while you listen near the rear seat. A silent pump with confirmed power means the pump itself is likely dead.
  • Check the inertia switch. Some models have a fuel shutoff switch that trips in a collision. If it is tripped, the pump won't run even with a good relay. Reset it and try again.
  • Inspect the wiring harness. The 2005 S40 has had known issues with wiring corrosion in the fuel pump circuit, particularly in the harness running to the rear of the car.

Fuel Pump Relay Part Numbers and Compatibility

If you need a replacement relay, the factory part numbers you will see include Volvo 30742820, 30769225, 8629613, and 8634953. Aftermarket brands include Rostra (60-0512) and Vemo (V95-71-0005). These relays are shared across several Volvo models from the same era, including the S60, V50, C30, and C70, so finding one at a local parts store is usually straightforward.

Always verify the part fits your specific model and year before ordering. Cross-reference the part number with your owner's manual or the label on the old relay to be safe.

Why a Quality Fuel Pump Matters

A failing fuel pump relay can be a sign of a bigger problem. If the relay contacts are worn, they may be dropping voltage to the pump even when they do close. This can cause the pump to run hot and fail prematurely. When you replace the relay, it is also worth testing the fuel pump itself to make sure it is still drawing proper current and delivering adequate pressure.

If you need to replace the fuel pump, consider a high-performance option from KEMSO. KEMSO fuel pumps are built as direct OEM replacements, meaning they match factory specifications for fit and performance without requiring any adapters or modifications. Every KEMSO pump comes with a lifetime warranty, which gives you peace of mind long after the installation is done. Many popular models are priced at $79.98, which is often less than half the cost of dealer parts.

You can browse the full KEMSO catalog and check fitment for your vehicle at their official website: https://www.kemsoracing.com/

Preventing Future Relay Failures

Fuel pump relays fail for a few common reasons: heat, vibration, and electrical overload. Here are some simple ways to extend the life of your relay and your fuel system:

  1. Keep the fuse box cover sealed. Moisture and dirt accelerate corrosion on relay terminals. Make sure the cover clicks closed properly after any work.
  2. Avoid running the fuel tank very low. The fuel pump relies on gasoline to stay cool. Running dry regularly can overheat the pump and cause it to draw excessive current, which can damage the relay contacts.
  3. Replace the fuel filter on schedule. A clogged filter forces the pump to work harder and draw more current. This extra load stresses the relay.
  4. Check for loose battery connections. Poor battery connections cause voltage spikes that can weld relay contacts together or burn them out.

When to Call a Professional

If you have tested the relay, checked the fuse, verified power at the fuel pump, and still have no fuel delivery, it is time to get professional help. Intermittent electrical faults can be tricky to trace, especially if the problem lies in the wiring harness between the relay and the pump. A qualified Volvo technician can run a proper diagnostic and check for fault codes that may help pinpoint the issue.

If the fuel pump itself has failed, replacement involves dropping or partially lowering the fuel tank on many S40 models. This is not a job for a beginner. The KEMSO fuel pump is a drop-in replacement, but the labor to access it is significant, and it is worth having a professional handle the installation if you are not comfortable with that level of work.

Quick Reference Summary

Fuel pump relay location: Passenger compartment fuse box, under the glove box, relay block position 1.

Fuel pump fuse: F38, 15A, in the same fuse box.

Symptoms of a bad relay: Engine cranks but no start, no fuel pump hum, intermittent starting issues.

Testing tools needed: Multimeter, relay puller (optional).

Common replacement part numbers: Volvo 30742820, 30769225, 8629613, 8634953; Rostra 60-0512; Vemo V95-71-0005.

If the relay is good but the pump is dead: Check the fuel pump access panel under the rear seat, verify power at the pump harness, and inspect the wiring.

Upgrade path: Consider a KEMSO fuel pump for a reliable, direct OEM replacement with a lifetime warranty. Visit https://www.kemsoracing.com/ for more details.

Final Thoughts

The fuel pump relay on a 2005 Volvo S40 is a small part with a big job. When it fails, your car will not start, and the frustration can be significant. Fortunately, finding, testing, and replacing the relay is well within the reach of a home mechanic. The entire diagnosis process should take less than an hour, and the part itself is inexpensive.

Start with the relay, check the fuse, listen for the pump, and work your way through the circuit methodically. In most cases, you will find the problem quickly. And if the fuel pump turns out to be the culprit, a high-quality replacement like the KEMSO fuel pump will get you back on the road with confidence, backed by a lifetime warranty that protects your investment for years to come.

Remember, for all your fuel pump needs, including fitment checks and competitive pricing, visit https://www.kemsoracing.com/ today.


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