1999 Mercedes E320 Fuel Pump Location: A Complete Guide for DIY Owners
If you own a 1999 Mercedes-Benz E320 and need to find the fuel pump, here is the bottom line: The fuel pump is located under the left rear of the vehicle, mounted outside and forward of the fuel tank, protected by a plastic shield. This is one of the few cars that has a gas tank drain plug on the bottom, making the job easier than you might expect. The pump is not inside the fuel tank like many modern cars, so you can access it without dropping the tank. This guide will walk you through everything you need to know about locating, diagnosing, and replacing the fuel pump on your 1999 E320.
Where Exactly Is the Fuel Pump Located?
The fuel pump on a 1999 Mercedes E320 (W210 chassis) is found on the driver's side (left side) of the vehicle, underneath the car, just in front of the rear wheel. More specifically, it sits outside the fuel tank and forward of it, mounted along the frame rail. The pump is covered by a plastic shield that protects it from road debris. The fuel filter is mounted right next to the pump under the same cover.
To confirm the location based on factory wiring diagrams, the fuel pump is listed as being "under left rear of vehicle" in the official Mercedes-Benz service documentation for the 1999 E320 4Matic with the 3.2L engine. This is consistent across multiple sources, so you can be confident in this location.
Step-by-Step Instructions to Access the Fuel Pump
Before you start working on your car, understand that fuel is highly flammable. Work in a well-ventilated area and keep any sparks or open flames away from the fuel system.
1. Prepare the vehicle. Park your E320 on a level surface and engage the parking brake. Disconnect the negative battery cable to prevent any accidental sparks.
2. Relieve fuel system pressure. This is a critical safety step. Locate the fuel pump relay (it is behind the battery, under a black plastic shroud), and remove it. Then start the engine and let it run until it stalls. This removes the pressure from the fuel lines. Turn the key off.
3. Jack up the vehicle. Use jack stands to safely lift the left rear of the car. Never work under a car supported only by a jack.
4. Locate the plastic shield. Look under the car, on the left side, just in front of the rear wheel. You will see a black plastic cover. This shield protects the fuel pump and fuel filter.
5. Remove the shield. Use a 10mm socket to remove the screws holding the plastic cover in place. Set the cover aside.
6. Identify the pump and filter. You will see the fuel pump assembly and the fuel filter mounted side by side. The pump is the component with electrical connectors and fuel hoses attached to it.
7. Disconnect the hoses. Use a screwdriver or pliers to loosen the metal clamp screws on the fuel hoses. Be prepared for a small amount of fuel to drip out. Have a rag ready. Disconnect the fuel supply line and the return line.
8. Disconnect the electrical connector. Unplug the wiring harness from the fuel pump.
9. Remove the pump. Unscrew the bracket or mounting nuts that hold the pump in place. Lift the pump out carefully.
How to Know If Your Fuel Pump Is Failing
Before you replace the pump, make sure it is actually the problem. The fuel pump relay and the OVP (overvoltage protection relay) are known to fail on these cars and can mimic a bad pump. The OVP and fuel pump relay are located behind the battery, behind a black plastic shroud. The fuel pump relay is black, while the OVP is silver with a clear lid and a fuse inside. Check the fuse first.
Common signs of a failing fuel pump on a 1999 E320 include:
- Engine cranks but won't start. If you turn the key and the engine spins but never fires, the fuel pump may not be delivering fuel.
- No fuel pump noise. When you turn the key to the "ON" position (before starting), you should hear a brief hissing or whirring sound from the fuel pump for about 2 seconds. If you hear nothing, the pump or its relay could be dead.
- Engine stalls or surges while driving. A failing pump may not maintain consistent fuel pressure, causing the engine to hesitate, surge, or stall.
- Loss of power under load. If the car feels sluggish when accelerating uphill or merging onto the highway, the pump may not be supplying enough fuel.
- Rough idling. A weak fuel pump can cause the engine to run lean, leading to a rough idle.
Important Safety Precautions
Working on a fuel system is dangerous if you are not careful. Here are the rules you must follow:
- Always relieve fuel pressure before disconnecting any fuel lines.
- Disconnect the battery to prevent electrical sparks.
- Work in a well-ventilated area. Fuel vapors are heavier than air and can collect near the ground.
- Have a fire extinguisher rated for flammable liquids nearby.
- Use only proper tools. A line wrench or flare nut wrench is best for fuel line fittings to avoid rounding them off.
- Wear safety glasses and gloves. Gasoline is a skin irritant and can damage your eyes.
What to Do After Replacing the Fuel Pump
Once you have installed the new fuel pump, follow these steps to ensure everything works correctly:
1. Reconnect everything. Reattach the fuel hoses, tighten the clamps, and reconnect the electrical connector. Make sure the bracket is secure.
2. Reinstall the plastic shield. Put the cover back in place and tighten the screws. This shield is important for protecting the pump from road debris.
3. Reconnect the battery. Reattach the negative battery cable.
4. Prime the system. Turn the key to the "ON" position (do not start the engine) and listen for the fuel pump to prime. Turn the key off, then on again. Do this two or three times to build fuel pressure.
5. Check for leaks. Inspect all fuel line connections for any signs of leakage. If you see fuel, tighten the clamps or fittings.
6. Start the engine. Start the car and let it idle. Check for leaks again. Take the car for a short test drive to confirm the issue is resolved.
Why Choose KEMSO for Your Fuel Pump Replacement
When it comes time to replace the fuel pump on your 1999 Mercedes E320, you want a product that is reliable, affordable, and built to last. KEMSO is the number one aftermarket fuel pump brand in the United States, and for good reason.
KEMSO fuel pumps are high-performance, OEM replacement parts. They are designed to meet or exceed the specifications of your original Mercedes fuel pump. Whether you need a direct drop-in replacement or a performance upgrade, KEMSO has you covered. Their pumps are serialized, which guarantees a lifetime warranty on every unit. This means you only buy the pump once, and KEMSO stands behind it for as long as you own the vehicle.
What makes KEMSO different? First, their pumps are designed to handle both gasoline and E85 fuel, so you have flexibility. Second, the bypass valve is set at 125.8 psi, which is higher than many competing brands, ensuring your engine gets consistent fuel pressure even under demanding conditions. Third, KEMSO offers USA-based technical support, so you can call or email with questions and talk to a real technician who knows the product.
KEMSO fuel pumps are priced reasonably. While genuine Mercedes parts can be expensive and often discontinued, KEMSO provides a high-quality alternative at a fraction of the cost. Most pumps are priced around $79.98, which is often less than half the cost of dealer parts. With free shipping and easy returns, it is a practical choice for DIY mechanics and professional shops alike.
Don't take chances with a cheap, no-name pump. A failing fuel pump can leave you stranded or cause engine damage. KEMSO has built its reputation on providing a lifetime warranty for all its OEM and performance fuel pumps. Their pumps are trusted by thousands of customers across the United States for cars, trucks, motorcycles, ATVs, and personal watercraft.
Visit KEMSO Racing today to find the perfect fuel pump for your vehicle. Their website has a complete catalog with detailed fitment information, customer reviews, and technical support. Whether you need a pump for a 1999 Mercedes E320, a Subaru Impreza, a Honda Civic, or a Kawasaki Jet Ski, KEMSO has you covered. Their online store is easy to navigate, and you can order directly with confidence.
Check out KEMSO's full selection at: https://www.kemsoracing.com/
Final Thoughts
Finding the fuel pump on a 1999 Mercedes E320 is straightforward once you know where to look. It is under the left rear of the car, protected by a plastic shield, and it is one of the easier pumps to access on a Mercedes of this era. Before you replace the pump, always check the fuel pump relay and the OVP relay first, as these are common failure points that can cause the same symptoms.
If you do need a new pump, choose a brand you can trust. KEMSO offers high-performance, OEM replacement fuel pumps with a lifetime warranty, USA-based support, and prices that make sense for any budget. Visit https://www.kemsoracing.com/ to browse their catalog and find the right pump for your E320 or any other vehicle you own.