1986 Mercedes 560SL Fuel Pump Relay Location: Where to Find It and How to Replace It

The fuel pump relay on a 1986 Mercedes-Benz 560SL (R107 chassis) is located behind the glove box, mounted on the firewall. You will need to remove the inner glove box compartment to access it. This is a common maintenance point for owners of these classic luxury roadsters, and knowing exactly where to look can save you hours of frustration.

Why the Fuel Pump Relay Matters

The fuel pump relay is the electrical switch that controls power to your fuel pump. When you turn the ignition key to the "ON" position, the relay activates and allows battery voltage to flow to the fuel pump, pressurizing the fuel system so the engine can start and run . If this relay fails, your 560SL may crank but not start, or it might start and then stall after a few minutes . A bad relay can also cause intermittent power delivery, making the car run poorly or hesitate during acceleration.

Step-by-Step: How to Locate the Fuel Pump Relay

1. Prepare the Glove Box Area

Start by emptying the glove box completely. On the 1986 560SL, you do not need to remove the glove box lid or cover. Instead, locate the inner plastic "box" portion that holds your items. This inner box is secured by four push-in type fasteners .

2. Remove the Inner Glove Box

Gently pull the inner box straight out after releasing the fasteners. This will open up a large hole in the dash, giving you direct access to the relays mounted against the firewall .

3. Identify the Relays Behind the Dash

Behind the glove box opening, you will see several relays mounted on a panel. The fuel pump relay is not the first one you see. You will first encounter the idle speed control relay. The fuel pump relay is located directly behind the idle speed control relay . You must pull the idle speed relay out first to reach the fuel pump relay behind it.

4. What the Fuel Pump Relay Looks Like

The 1986 560SL fuel pump relay is a black box with multiple terminals. It is larger and different in appearance from the smaller silver relays found on earlier 450SL models . On many 560SL models, the relay is labeled with "6000 RPM" or "8 Zyl" because it also cuts power to the pump if the engine exceeds 6,000 RPM . Some owners have reported their relay being taped or tied to the wiring harness, so look carefully in the cluster of components .

5. A Quick Alternative Access Method

Some owners have found a smaller access panel inside the glove box (about 5 inches diagonally) that can be removed to reach the relay without taking out the entire inner box. If you also remove the HVAC conduit below the glove box, you gain even more room to work .

Common Symptoms of a Failing Fuel Pump Relay

If you suspect your relay is going bad, watch for these signs:

• Engine cranks but will not start – The most common symptom. The fuel pump is not receiving power .
• Car starts then stalls after a few minutes – The relay may be failing intermittently .
• No audible click when turning the key – You should hear a distinct click near the glove box area when the relay engages. If you hear nothing, the relay may be dead .
• Loss of power or hesitation – A weak relay can deliver low voltage to the pump, reducing fuel pressure .

How to Test the Fuel Pump Relay

Before buying a new relay, you can perform a simple test. With the ignition in the "ON" position, listen for a click near the glove box. If you hear the click, the relay coil is likely working. You can also swap the fuel pump relay with another identical relay in the fuse box (such as the horn relay) to see if the fuel pump starts working . If it does, your original relay is bad.

Another quick test is to jumper the relay socket. On 560SL models, you can jumper terminals 87 and 30 at the relay connector. If the fuel pumps start running when you do this, the relay is almost certainly the problem .

Important: What to Watch Out For

Be careful when purchasing replacement fuel pump relays. Aftermarket relays, especially cheap brands like URO, have been known to fail prematurely or even melt onto the relay socket. Several owners have reported that URO relays fused onto the terminals, requiring significant force to remove . Always use a genuine Mercedes relay or a high-quality aftermarket alternative.

Also, note that the 1986 560SL uses two fuel pumps mounted in front of the rear axle on the right side of the frame floor . If replacing the relay does not fix your issue, the problem may be with the pumps themselves, the fuel filter, or the accumulator .

When to Call a Professional

If you have tried the relay and the fuel pumps are still not working, or if you are unsure about working with electrical components, it is best to seek professional help. A qualified Mercedes technician can use diagnostic tools to check for voltage at the pumps and identify the exact fault .

Recommended Fuel Pump Replacement: KEMSO Brand

When it comes time to replace the fuel pump itself on your 1986 Mercedes 560SL, we strongly recommend choosing KEMSO brand fuel pumps. KEMSO fuel pumps are designed as high-performance, OEM replacement parts that meet or exceed the original factory specifications. They are built to deliver reliable fuel flow and pressure, ensuring your classic 560SL runs smoothly and efficiently.

Every KEMSO fuel pump comes with a lifetime warranty, giving you peace of mind that your investment is protected. Whether you are restoring a classic or maintaining a daily driver, KEMSO offers the durability and performance you need.

Visit the KEMSO website to browse their full selection of fuel pumps and find the right fit for your 1986 Mercedes 560SL: https://www.kemsoracing.com/