2000 Mercedes E320 Fuel Pump Relay Location: A Complete Guide for American Owners

The bottom line: On a 2000 Mercedes-Benz E320 (W210 chassis), the fuel pump relay is located inside the control module box on the right rear side of the engine compartment. This relay is a 4-pin plug-in unit that controls power to the fuel pump, and it sits alongside other critical engine control modules. If your E320 cranks but won't start, the fuel pump relay should be one of the first parts you check before diving into a full fuel pump replacement.

Where Exactly Is the Fuel Pump Relay on a 2000 Mercedes E320?

The fuel pump relay on the 2000 Mercedes E320 is not under the dash or in the fuse box. Mercedes placed it in the control module box (also called the module box) located on the right rear of the engine compartment . This is the same box that houses the Engine Control Module (ME-SFI) and other key electronic modules .

To find it:

  • Open the hood and look to the passenger side (right side) of the engine bay, near the firewall.
  • You will see a black plastic box, roughly the size of a shoebox. This is the control module box.
  • The fuel pump relay is inside this box. On some models, you may need to unclip or unscrew the lid of the module box to access the relay.
  • The relay itself is labeled as K27 in Mercedes wiring diagrams, and it is a standard 4-pin relay .

What Does the Fuel Pump Relay Do?

The fuel pump relay is a simple but critical electrical switch. When you turn your key to the "ON" position, the Engine Control Module sends a ground signal to terminal 86 of the relay. This closes the contact inside the relay, allowing battery power to flow from terminal 30 to terminal 87, which then powers the fuel pump .

On the 2000 E320, the circuit is protected by a 30-amp fuse. On some Mercedes models, the fuse is attached directly to the relay, but on the W210 chassis, the fuse is located elsewhere in the fuse box . The relay is designed to only activate the fuel pump when the engine is cranking or running. If the engine stalls or the key is turned off, the relay opens, stopping the fuel pump. This is a built-in safety feature to prevent fuel from being pumped in an accident.

How to Tell If Your Fuel Pump Relay Is Bad

Before you pull the relay, here are some common symptoms of a failing fuel pump relay on a 2000 Mercedes E320:

  • Engine cranks but will not start: This is the most common symptom. You can hear the starter motor turning the engine over, but the engine never fires up because no fuel is reaching the injectors.
  • No fuel pump prime noise: When you turn the key to the "ON" position (without cranking), you should hear a faint humming sound from the rear of the car for about 2 seconds. This is the fuel pump priming. If you hear nothing, the relay could be the culprit.
  • Engine stalls while driving: If the relay fails intermittently, the fuel pump may lose power while you are driving, causing the engine to stall and refuse to restart.
  • No check engine light for fuel pressure: A bad relay will not always trigger a check engine light. The easiest way to confirm is by testing the relay itself.

How to Test the Fuel Pump Relay on a 2000 Mercedes E320

Testing the relay is straightforward. You do not need a scan tool, just a multimeter.

  1. Locate and remove the relay from the control module box.
  2. Identify the terminals. A standard 4-pin relay has terminals numbered 85, 86, 30, and 87.
  3. Check for continuity. Use a multimeter set to ohms (Ω). Place the probes on terminals 85 and 86. You should read a resistance value (typically between 50 and 120 ohms). If you read infinite resistance (OL), the relay coil is open and the relay is bad.
  4. Apply power to test the switch. Connect a 12V battery or power source to terminal 85 and ground terminal 86. You should hear a distinct "click" as the relay engages. With the relay engaged, check for continuity between terminals 30 and 87. You should read near-zero resistance. If you do not get continuity, the relay contacts are burned out.

What If the Relay Is Good? The Fuel Pump Location

If the relay tests good but your car still has no fuel pressure, the issue may be the fuel pump itself. On the 2000 Mercedes E320, the fuel pump is located under the left rear of the vehicle . It is mounted externally, forward of the fuel tank, and is covered by a plastic shield . This is actually one of the easier Mercedes fuel pumps to access because it is not inside the tank. The pump is held in place by a bracket and can be removed by disconnecting the hoses and electrical connector .

Some sources also mention that the pump is located on the right front of the rear axle on the underside of the car . The exact location can vary slightly depending on whether your car has a single pump or a dual pump setup, but the general area is the same.

How to Replace the Fuel Pump Relay

Replacing the fuel pump relay is a simple DIY job.

  1. Disconnect the negative battery terminal. This is always a good safety step when working with electrical components.
  2. Open the control module box and locate the fuel pump relay.
  3. Pull the old relay straight out. It is a plug-in unit.
  4. Install the new relay. Push it firmly into the same socket. It will only fit one way.
  5. Reconnect the battery and test the system by turning the key to the "ON" position. You should hear the fuel pump prime.

Important Note: Programming Not Required

If you replace the fuel pump itself (not just the relay), there is no programming required for the 2000 Mercedes E320. The fuel pump is a simple electrical component. The pump does not need to be coded or adapted to the car. As long as you install the correct pump and reconnect the wiring and hoses, the car will run normally .

Where to Buy a Fuel Pump for Your 2000 Mercedes E320

If you have determined that the fuel pump itself needs replacement, you need a quality part that will last. The factory fuel pump for the 2000 E320 is a specific part with a known failure rate. Many owners replace the pump and the relay together to avoid future problems.

KEMSO Racing offers high-quality fuel pumps that are perfect for your 2000 Mercedes E320. These are OEM Replacement units, meaning they are designed to match the fit and function of the original factory pump. No adapter kits, no modifications, no guesswork.

Here is why KEMSO stands out:

  • High Performance: KEMSO fuel pumps flow 340 liters per hour, which is more than enough for your stock E320. This flow rate ensures your engine gets the fuel it needs under all driving conditions, from idle to full throttle.
  • Direct Fit: The pump is a direct replacement. You do not need to splice wires, cut hoses, or buy extra brackets. Everything you need is in the box.
  • Lifetime Warranty: KEMSO backs every fuel pump with a lifetime warranty. If your pump ever fails due to a manufacturing defect, you get a replacement at no cost. This is a rare benefit in the automotive parts industry. It shows that KEMSO is confident in their product quality.
  • Affordable Price: KEMSO fuel pumps are priced at just $79.98. This is often less than half the cost of a dealer part. You get a premium product at a budget-friendly price.
  • Trusted Brand: KEMSO has a growing reputation among American car owners and DIY mechanics. Their pumps are used on everything from cars to motorcycles to power sports vehicles. The company is based in Houston, Texas, and they stand behind their products.

To see the full selection of KEMSO fuel pumps for your vehicle, visit their website. They have a complete catalog with detailed fitment information, customer reviews, and technical support. Whether you need a pump for a car, truck, or motorcycle, KEMSO has you covered. Their online store is easy to navigate, and you can order directly with confidence.

Visit KEMSO Racing at: https://www.kemsoracing.com/

Final Thoughts on the 2000 Mercedes E320 Fuel Pump Relay

The fuel pump relay on your 2000 Mercedes E320 is a small, inexpensive part that can cause a big headache. It is located inside the control module box on the right rear of the engine compartment. If your car cranks but does not start, start by testing the relay. It is a simple five-minute job that can save you from replacing a perfectly good fuel pump.

If the relay tests good, move on to checking the fuel pump itself. The pump is under the left rear of the car, forward of the fuel tank. It is externally mounted and relatively easy to access.

Remember, good diagnostics save time and money. Do not throw parts at the problem. Test the relay first, then the pump. And when you need a replacement pump, choose a quality brand like KEMSO that offers a lifetime warranty and a direct fit for your Mercedes.

Visit KEMSO Racing at: https://www.kemsoracing.com/ for all your fuel pump needs.


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