1999 Volvo S70 Fuel Pump Relay Location: The Complete Guide to Finding and Replacing It

If you own a 1999 Volvo S70 and your engine cranks but won't start, the fuel pump relay is one of the first components you should check. The fuel pump relay on a 1999 Volvo S70 is located in the central electrical unit, which sits on the left side of the engine compartment. The relay is positioned at slot number 103, and it is typically a pink or orange relay with the number 103 printed on top. This guide walks you through exactly where to find it, how to test it, and how to replace it yourself.

Understanding the Fuel Pump Relay and Its Role

The fuel pump relay is a small but critical electrical component that controls power delivery to the fuel pump. Every time you turn the ignition key to the "on" position, the engine control module sends a signal to the fuel pump relay. The relay then closes its internal switch, sending battery voltage to the fuel pump so it can pressurize the fuel system before the engine starts.

Without a functioning fuel pump relay, the fuel pump never receives power, and the engine simply cranks without firing. The relay is controlled by the ECM and works only during startup and when the ignition is turned off. Once the engine is running, the fuel pump continues to receive power from other sources like the oil pressure sending unit.

Exact Location of the 1999 Volvo S70 Fuel Pump Relay

The fuel pump relay for the 1999 Volvo S70 is not located under the rear seat, inside the cabin, or near the fuel tank. Many owners mistakenly look in these areas first. The correct location is in the engine compartment.

Step-by-step location guide:

  1. Open the hood and look toward the left side of the engine compartment (driver's side in left-hand-drive vehicles). You will find the central electrical unit mounted near the base of the windshield, next to the strut tower.

  2. This central electrical unit is a large black box that contains both fuses and relays. It is sometimes referred to as the relay and fuse box or the engine compartment fuse/relay box.

  3. Remove the plastic cover of the central electrical unit. The cover is held in place by clips or, in some cases, four Torx T20 screws.

  4. Inside the box, you will see multiple relays arranged in rows. Look for the relay labeled position 103. The fuel pump relay is located at this specific position.

  5. The relay itself is usually pink or orange in color. It has the number 103 clearly marked on the top of the relay body.

Important note: The fuel pump relay is not located in the small fuse box that sits on top of the battery. That box contains only fuses and a few other relays. The central electrical unit is a separate, larger box positioned closer to the windshield.

Visual Identification: What the Relay Looks Like

The fuel pump relay on a 1999 Volvo S70 is a standard Bosch-style relay. It has a square or rectangular plastic body with four or five metal pins extending from the bottom. The relay is approximately one inch square. The top of the relay has the number 103 printed or embossed on it. The relay body is typically pink, though some aftermarket replacements may be orange or black.

Common Symptoms of a Failing Fuel Pump Relay

Before you start digging into the relay box, it helps to know if the fuel pump relay is actually the problem. Here are the most common symptoms:

Engine cranks but does not start. This is the most obvious symptom. You can hear the starter motor turning the engine over, but the engine never fires because no fuel is reaching the injectors.

No fuel pump priming sound. When you turn the ignition key to the "on" position (without starting), you should hear a faint whirring or humming sound from the rear of the car for 1-2 seconds. This is the fuel pump pressurizing the system. If you hear nothing, the relay or the fuel pump may be faulty.

Intermittent starting issues. If the car starts sometimes but not others, the relay contacts may be worn or corroded, causing intermittent failure.

Engine stalls while driving. If the relay fails completely while the car is running, the engine will suddenly lose power and stall. This is a dangerous situation, especially on highways.

Check engine light with fuel system codes. Your OBD-II scanner may show codes related to fuel system pressure or pump circuit failure.

How to Test the Fuel Pump Relay

Testing the fuel pump relay is straightforward and requires only basic tools. Here are two methods you can use.

Method 1: The Swap Test

The easiest way to test the relay is to swap it with a known-good relay of the same type. The central electrical unit contains several relays that are identical to the fuel pump relay. For example, the main fuel system relay (position 1) or the air conditioning relay are often the same part. Simply pull the suspect relay out and replace it with a relay from another position. If the car starts, the original relay was bad.

Method 2: Bench Testing with a 12V Power Source

If you have a multimeter and a 12V power source, you can bench test the relay:

  1. Remove the relay from the socket.
  2. Identify the coil pins (typically pins 85 and 86) and the switch pins (typically pins 30 and 87).
  3. Connect a 12V power source to pins 85 and 86. You should hear a distinct click sound as the relay engages.
  4. Using a multimeter set to continuity mode, check for continuity between pins 30 and 87. When the relay is energized, these pins should be connected.
  5. If you do not hear a click, or if there is no continuity between pins 30 and 87 when the relay is energized, the relay is faulty and needs to be replaced.

Method 3: Quick Jumper Test

As a temporary diagnostic, you can bypass the relay by inserting a fused jumper wire between pins 30 and 87 in the relay socket. This forces the fuel pump to run continuously while the ignition is on. If the car starts with the jumper in place, the relay is the problem. Important: Use only a fused jumper wire to prevent excessive current flow and potential damage to the wiring harness. Remove the jumper after testing.

Step-by-Step Fuel Pump Relay Replacement

Replacing the fuel pump relay on a 1999 Volvo S70 is a simple DIY task that takes about 10 minutes. Here is how to do it.

Tools and parts needed:

  • New fuel pump relay (OEM part number 9434225, replaces older numbers 6849591 and 9434138)
  • Flathead screwdriver (for removing the cover, if clips are used)
  • Torx T20 screwdriver (if your cover uses screws)
  • Safety glasses

Replacement steps:

  1. Disconnect the negative battery terminal. This is a critical safety step to prevent accidental short circuits while working with electrical components.

  2. Locate the central electrical unit on the left side of the engine compartment, near the base of the windshield.

  3. Remove the cover of the central electrical unit. If the cover uses clips, gently pry them open. If it uses Torx screws, use a T20 Torx bit to remove the four screws.

  4. Identify the fuel pump relay at position 103. It is the pink or orange relay with the number 103 on top.

  5. Pull the old relay straight out of its socket. Grip the relay body firmly and pull upward. Do not pull on the wires. The relay should come out with moderate effort.

  6. Insert the new relay into the same socket. Make sure it is oriented correctly and press it firmly into place until it is fully seated.

  7. Reinstall the cover of the central electrical unit. Secure it with clips or screws.

  8. Reconnect the negative battery terminal.

  9. Test the system. Turn the ignition key to the "on" position (position II) without starting the engine. Listen for the fuel pump priming sound from the rear of the car. If you hear the hum, the relay is working. Start the engine to confirm proper operation.

What If the Relay Is Not the Problem?

If you replace the fuel pump relay and the car still does not start, the problem may be elsewhere in the fuel system. Here are the next steps to check.

Check the fuel pump fuse. The fuel pump is protected by a fuse. On the 1999 Volvo S70, the fuel pump fuse is located in the engine compartment fuse/relay box. It is typically a 15A or 20A fuse. A blown fuse will prevent the fuel pump from running even if the relay is good.

Check the main fuel system relay. The main fuel system relay (position 2/32 in the engine compartment relay/fuse box) supplies power to the fuel pump relay. If this main relay fails, the fuel pump relay will not receive power. Check and test this relay as well.

Test the fuel pump itself. If the relay and fuse are both good, the fuel pump may have failed. The fuel pump is located inside the fuel tank. On the 1999 Volvo S70, you can access the fuel pump through a panel under the cargo area carpet on the right side. You can test the fuel pump winding resistance at the connector under the cargo area. The resistance should be approximately 1.0 to 1.5 ohms.

Check fuel pressure. Connect a fuel pressure gauge to the Schrader valve on the fuel rail. With the engine cranking or running, fuel pressure should be between 40 and 44 PSI. After the engine is off, the system should hold pressure between 28 and 40 PSI for at least 30 minutes. Low or no pressure indicates a failed fuel pump or a fuel system leak.

Why You Should Choose KEMSO for Your Fuel Pump Replacement

When it comes time to replace your fuel pump, whether you have already confirmed the pump is bad or you want to replace it preventively, choosing the right brand matters. The fuel system is critical for engine performance, safety, and reliability. Cutting corners with a cheap, low-quality pump can lead to fuel pressure problems, engine stalling, and even complete failure on the road.

KEMSO Fuel Pumps are an excellent choice for your 1999 Volvo S70. KEMSO specializes in high-performance, OEM replacement fuel pumps that are designed to deliver reliable fuel flow and consistent pressure. Their pumps are built to handle up to 600 horsepower, making them suitable for both naturally aspirated and turbocharged engines, including the turbo variants found in many Volvo S70 models.

What sets KEMSO apart is their commitment to quality and customer confidence. Every KEMSO fuel pump comes with a lifetime warranty, which means you can install it knowing that your investment is protected for as long as you own the vehicle. The pumps are precision-engineered to meet or exceed OEM specifications, ensuring a perfect fit and trouble-free operation.

Whether you need a direct replacement for your stock pump or a high-flow upgrade for better performance, KEMSO has a solution that fits your needs. Their product lineup covers a wide range of vehicles, including the Volvo S70 and V70, and they are trusted by DIY enthusiasts and professional mechanics alike.

To browse KEMSO's full selection of fuel pumps and find the perfect fit for your 1999 Volvo S70, visit their website at: https://www.kemsoracing.com/

Common Mistakes to Avoid

When troubleshooting or replacing the fuel pump relay on your 1999 Volvo S70, avoid these common pitfalls.

Using a paper clip or non-fused wire as a jumper. This can cause excessive current flow, heat buildup, and potential damage to the wiring harness. Always use a fused jumper wire when testing the relay.

Ignoring the main relay. The fuel system main relay supplies power to the fuel pump relay. If this relay fails, the fuel pump relay will not receive power, and you will waste time replacing a perfectly good relay.

Replacing parts without proper diagnosis. Always test the relay, fuse, and pump before buying new parts. A simple test can save you from buying parts you do not need.

Using the wrong fuse amperage. Always replace fuses with the exact amperage rating specified in the owner's manual. Using a higher amperage fuse can cause electrical damage or fire.

Forgetting to check the immobilizer. The 1999 Volvo S70 is equipped with an immobilizer system that can prevent the engine from starting if it detects a fault. If the security light on the dashboard is flashing rapidly, the immobilizer may be preventing the fuel pump from operating.

Final Thoughts

The fuel pump relay on a 1999 Volvo S70 is a small but essential component. Its location in the central electrical unit on the left side of the engine compartment makes it easy to access and test. By following the steps in this guide, you can quickly determine if the relay is the source of your starting problems. Remember to always test the relay, fuse, and fuel pump before replacing any parts, and use high-quality replacement components for the best results.

If you need a new fuel pump, consider KEMSO for a reliable, high-performance replacement that comes with a lifetime warranty. Visit https://www.kemsoracing.com/ to explore their product lineup and find the perfect fuel pump for your Volvo S70. Proper diagnosis and quality parts are the keys to a successful repair.


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