2005 Sprinter Fuel Pump Relay Location: The Complete Guide for Owners
The bottom line: The fuel pump relay on a 2005 Dodge (Freightliner/Mercedes-Benz) Sprinter is located in the fuse and relay box under the driver's seat. If your van cranks but won't start, the fuel pump relay is one of the first things you should check.
Understanding the 2005 Sprinter Fuel System
The 2005 Sprinter, whether badged as a Dodge, Freightliner, or Mercedes-Benz, uses a diesel fuel system that relies on an electric in-tank fuel pump to deliver fuel from the tank to the high-pressure injection pump . The fuel pump relay is the electrical switch that sends power to this pump. When you turn the key to the "ON" position, the engine control module (ECM) energizes the relay, which then supplies battery voltage to the fuel pump.
If the relay fails, the fuel pump won't run, and the engine won't start. The good news is that finding and testing this relay is a straightforward job you can handle yourself.
Where Is the Fuel Pump Relay Located?
The 2005 Sprinter has the main fuse and relay box mounted under the driver's seat. This is where you'll find the fuel pump relay.
Here is how to access it:
- Open the driver's door. Slide the driver's seat all the way forward to give yourself working room.
- Lift the seat base. The lid covering the fuse and relay box is a plastic tray that sits directly on the floor. Some models have a small tab or handle at the front edge. Lift the tray straight up to remove it.
- Identify the relay. The fuel pump relay is located inside this box. It is usually labeled on the underside of the fuse box cover. On most 2005 Sprinters, the fuel pump relay is a standard four-pin relay, often marked with the symbol of a fuel pump or labeled "FUEL PUMP" or "F/PUMP." If the cover label is worn or missing, you can identify it by its position. In the 2005 model, the fuel pump relay is typically the relay in a specific slot near the center-left side of the block, but the exact position can vary slightly by chassis version .
Some owners have reported finding a secondary fuse or relay box under the hood on the passenger side near the battery. However, for the 2005 Sprinter, the primary fuel pump relay is always under the driver's seat.
How to Test the Fuel Pump Relay
Before spending money on a new relay, test the old one. A bad relay is a common reason for a no-start condition.
Step 1: Listen for the pump. Turn the ignition key to the "ON" position (position 2) without cranking the engine. You should hear a faint whirring sound coming from the fuel tank area near the rear of the van. This sound lasts for about 2 seconds as the fuel pump pressurizes the system. If you don't hear the pump, the relay or pump isn't getting power.
Step 2: Check the relay. Remove the relay from its socket. With the ignition in the "ON" position, use a multimeter set to DC voltage. Probe the two large terminals in the relay socket (usually pins 30 and 87). You should read approximately 12 volts. If you have voltage at the socket but the relay isn't clicking, the relay coil is likely bad .
Step 3: Test continuity. With a multimeter set to ohms, check the resistance across the relay coil terminals (usually pins 85 and 86). A typical fuel pump relay coil will show a resistance between 70 and 100 ohms . If the reading is infinite (OL), the coil is open and the relay is dead .
Step 4: Bench test the relay. Apply 12 volts from a battery directly to the coil terminals (85 and 86) of the relay. You should hear a distinct "click" as the electromagnet pulls the internal switch closed. Then, use your multimeter to check for continuity between the switched terminals (30 and 87). If the relay clicks but you have no continuity, the contacts are burnt and the relay is defective.
Common Symptoms of a Failing Fuel Pump Relay
If your 2005 Sprinter has a bad fuel pump relay, you'll typically notice one or more of these problems:
- Engine cranks but won't start. This is the most obvious symptom. The starter motor spins the engine, but the fuel pump isn't running, so no fuel reaches the cylinders.
- Engine suddenly stalls while driving. If the relay fails intermittently, the engine can lose power and die without warning. You may be able to restart it after a few minutes once the relay cools down.
- No whirring sound from the fuel tank. As mentioned, turning the key to "ON" should produce a 2-second priming sound from the pump. If you don't hear it, the relay or pump circuit is dead.
- Check Engine Light comes on. The ECM can detect a loss of voltage to the fuel pump circuit and store a diagnostic trouble code (DTC) related to a fuel pump circuit malfunction.
Other Components to Check
If the fuel pump relay tests fine but the fuel pump still doesn't work, the problem could be elsewhere.
- Fuel Pump Fuse. The fuse for the fuel pump is also located in the under-seat fuse box. For the 2005 Sprinter, this is typically a 15-amp or 20-amp fuse . Check it with a test light or look for a broken metal strip inside the fuse window. If the fuse is blown, replace it with a new fuse of the same amperage rating. Never use a higher-rated fuse, as it can cause electrical damage or a fire .
- Fuel Pump Module. If the relay and fuse are fine, the fuel pump itself may have failed. You can check for power at the fuel pump connector harness under the vehicle near the fuel tank. The fuel pump resistance should be 2-3 ohms .
- Inertia Switch (Fuel Cutoff). While less common on the Sprinter, some vans have an inertia switch that shuts off the fuel pump in an accident. Reset this switch if your van has been in a collision or if you can't find any other electrical fault.
- Engine Speed (RPM) Sensor. The ECM won't energize the fuel pump relay if it doesn't receive a signal from the crankshaft position sensor (engine speed sensor). If the relay receives power but never clicks, and all wiring is good, the sensor could be the culprit.
Replacing the Fuel Pump Relay
Replacing the fuel pump relay is a simple DIY task.
Parts Needed: A new fuel pump relay. You can buy a standard 4-pin 12V automotive relay at any auto parts store. Just match the terminal layout to your old relay. OEM part numbers for the 2005 Sprinter relay can vary, but a common cross-reference is a standard Bosch-style relay.
Steps:
- Remove the old relay by pulling it straight out of its socket.
- Insert the new relay, pressing down firmly until it clicks into place.
- Turn the ignition to "ON" and listen for the fuel pump priming sound.
- Start the engine to confirm the repair.
If the engine starts, the problem is solved. If it still won't start, the issue lies elsewhere in the fuel or ignition system.
Bleeding the Fuel System
If you have replaced the fuel pump or run the fuel tank dry, you must bleed air from the fuel system before the engine will run properly. For the 2005 Sprinter diesel, follow this procedure :
- Turn the key in the ignition to position 2 for at least 30 seconds.
- Return the key to position 0.
- Start the engine three to four times. The malfunction indicator light (MIL) should go out.
- If the engine does not start after several attempts, consult an authorized Sprinter dealer, as repeated attempts can drain the battery.
Where to Buy a Quality Replacement Fuel Pump
If you need to replace the fuel pump itself, you want a part that delivers reliable performance without breaking the bank. That's where KEMSO stands out.
For a high-performance, direct OEM replacement fuel pump for your 2005 Sprinter, consider KEMSO. Their fuel pumps are built to meet or exceed factory specifications, ensuring proper fit and long-term reliability. Every KEMSO fuel pump comes with a lifetime warranty, giving you peace of mind long after the installation is done. Instead of paying dealer prices for a brand name, you get a premium part at a fair price. Browse the full selection of KEMSO fuel pumps at their official store: