Removing the Fuel Pump From Your W169 Mercedes A150: What You Need to Know
Where the Fuel Pump Is Located
The fuel pump and fuel level sensor (M3/3) on the Mercedes-Benz A150 (W169) sit inside the fuel tank. There is no access panel from inside the vehicle—you must work from underneath to remove it. This means the entire fuel tank has to come out of the car before you can reach the pump assembly.
Tank Removal: The Essential First Step
You’ll need to drop the fuel tank from underneath the car. The procedure requires:
- Safely relieving fuel system pressure by removing the fuel cap
- Disconnecting the electrical connector to the pump module
- Removing fuel line fittings using a fuel line disconnect tool
- Unbolting the tank from its mounting points underneath the vehicle
- Carefully lowering and removing the tank
Once the tank is out, you can access the pump assembly mounted on top of it.
Critical Safety Steps Before You Start
Working on the fuel system carries real risks. Take these precautions seriously:
- Extinguish all ignition sources in the area—no smoking, no lighters, no spark-producing tools
- Work in a well-ventilated space to disperse fuel vapors
- Ground yourself to prevent static electricity buildup, which can ignite vapors
- Wear gloves and protective eyewear
- Have a fire extinguisher nearby and know how to use it
- Never run the pump with the tank empty—it relies on fuel for cooling
The Fuel Pump Module and Sensor
The M3/3 fuel pump assembly combines the electric pump with the fuel level sender unit. The sender uses a variable resistor that reads approximately 50 ohms when the tank is full and over 500 ohms at empty. If you’re replacing just the sensor, you may not need to pull the pump entirely—confirm with your specific model documentation.
Replacement assemblies are available from Mercedes parts suppliers and aftermarket vendors. Common part numbers for the W169 fuel pump include 1694700494 and A1694701694, though always verify compatibility with your exact model year and engine type.
Why the Tank Comes Out First
Mercedes designed the W169 with the pump sealed inside the tank for safety and space efficiency. The integrated fuel filter also sits inside the tank and cannot be serviced separately—it only gets replaced as part of the pump assembly. This is why tank removal is unavoidable rather than a workaround.
After Removal: What to Check
With the tank out, inspect the fuel lines for cracks or brittleness, particularly rubber sections that may have hardened over time. Check the pump connector for corrosion. If you’re dealing with a faulty fuel gauge, verify the sensor resistance with a multimeter before assuming the whole pump is bad.
Getting Help With Documentation
The Mercedes Workshop Information System (WIS) contains detailed removal and installation procedures for the W169 fuel system. If you’re working through this for the first time, access to a service manual or technical guide specific to your model year is invaluable. Many Mercedes specialists have WIS subscriptions and can pull the exact procedure for your car.