Replacing Fuel Pump In S430: Step-By-Step Guide

If your 2008 S430 is experiencing hard starting, stalling, or poor acceleration, you may need to replace the fuel pump. The fuel pump is located inside the fuel tank and can be accessed through an access panel above the tank in the passenger compartment. The cost of a fuel pump replacement varies, but on average, it costs around $700, with $345 for parts and $357 for labor.

Fuel pump location and removal

The fuel pump on a 2008 S430 is located inside the vehicle's gas tank. To replace it, you will need to remove the gas tank from the vehicle. Here are the steps to replace the fuel pump:

First, you will need to raise the vehicle and secure it on safety stands. Then, drain the fuel from the tank. Next, lower the fuel tank from the vehicle to gain access to the pump. Once the tank is lowered, remove the fuel pump supply and return hoses, EVAP system hoses, and electrical connections to the pump.

Now, you can remove the fuel pump. If there is an access panel above the tank in the passenger compartment, you can remove the pump through there. If not, you will need to remove the fuel tank to access the pump.

After removing the old pump, install the new pump, along with any reusable brackets and pickup screens. Reattach the hoses and electrical connections. Finally, fill the tank with fuel and run the engine to test for leaks.

Please note that it is important to keep the gas tank at least a quarter full after installing a new fuel pump to maximize its lifespan.

Fuel pump testing

To test the fuel pump of a 2008 S430, you must first check for common symptoms of a faulty fuel pump. These may include:

• The car won't start or unexpectedly stalls and won't restart.
• The check engine light is on.
• A whirring noise from the fuel tank.

If you experience any of the above issues, you should then test the fuel pump to confirm it isn't functioning. Prior to replacing the pump, a mechanic will power it directly to confirm that the issue is a failed pump rather than a faulty power supply.

If the fuel pump is indeed faulty, you can then proceed to replace it. Here is a general step-by-step guide on how to do so:

• Remove the fuel pump from the tank through an access panel above the tank in the passenger compartment. If no access panel exists, drain the fuel from the tank and then lower the fuel tank from the vehicle to gain access to the pump.
• Remove the fuel pump supply and return hoses, EVAP system hoses, and electrical connections to the pump.
• Once the pump is out, attach any reusable brackets and pick-up screens to the new pump, then install the new pump.
• If the fuel system uses an in-line external filter, replace the filter. Re-establish all hoses and electrical connections.
• Add fuel to the tank and run the engine to test for leaks.

Fuel pump installation

Step 1: Testing the fuel pump

Before installing a new fuel pump, it is important to test the existing pump to confirm that it is faulty.

Step 2: Removing the fuel pump

The fuel pump is located in the vehicle's gas tank. If there is an access panel above the tank in the passenger compartment, the pump can be removed through there. If not, the fuel must first be drained from the tank, and then the tank must be lowered from the vehicle to access the pump.

Step 3: Disconnecting hoses and connections

Once the fuel pump is accessible, the next step is to disconnect the fuel pump supply and return hoses, EVAP system hoses, and electrical connections to the pump.

Step 4: Installing the new fuel pump

Any reusable brackets and pick-up screens are then attached to the new fuel pump. If the fuel system uses an in-line external filter, it should be replaced at this point. The new pump can then be installed in the fuel tank. All hoses and electrical connections can then be re-established.

Step 5: Testing the new fuel pump

Finally, fuel is added to the tank, and the engine is run to test for leaks.

Additional considerations

• It is recommended to replace the fuel filter when replacing the fuel pump, unless it has been replaced recently.
• When the fuel tank is lowered during the repair, the fuel tank straps and fasteners should be checked for excessive corrosion and replaced if necessary.
• To maximise the life of the new fuel pump, it is advisable to keep the gas tank at least a quarter full.

Fuel pump relay location

The fuel pump relay, also known as the relay switch, is a black plastic component that controls the current sent to the fuel pump. It is usually located under the hood or under the dashboard, near the steering wheel. In the case of the Mercedes-Benz S430, the fuel pump relay can be found underneath the rear seat on the left side.

To replace the fuel pump relay, follow these steps:

• Raise and support the vehicle hood.
• Remove the defective fuel pump relay.
• Install the new fuel pump relay.
• Test the fuel pressure and clear codes with a scanner or gauge.
• Close the vehicle hood and road test for proper operation.

Fuel pump cost

The cost of replacing a fuel pump on a 2008 Mercedes-Benz S430 can vary depending on location, but on average, it costs around $702, with $345 for parts and $357 for labor.

For a certified mechanic to come to your home or office, the price can range from $1243.99 to $1977.92. This service includes a 12-month/12,000-mile warranty, a free 50-point safety inspection, and upfront, transparent pricing.

If you are only replacing the fuel pump relay, the cost is significantly lower, averaging $149 with $54 for parts and $95 for labor.

There are a variety of fuel pumps and fuel pump relays compatible with the Mercedes-Benz S430 available for purchase online, with prices ranging from $44.99 to $177.

It is important to note that the fuel pump is a critical component of your vehicle, and attempting to replace it yourself may void any warranties. It is always recommended to consult a qualified mechanic for any repairs or replacements.

Frequently asked questions