2004 Chrysler 300M Fuel Pump Replacement: A Complete Step-by-Step Guide

The bottom line: Replacing the fuel pump on your 2004 Chrysler 300M is a job you can do yourself if you have moderate mechanical experience, but it requires dropping the fuel tank or accessing the pump through a rear seat panel. The fuel pump is located inside the fuel tank and is part of a complete fuel pump module assembly that includes the fuel level sending unit and pressure regulator . Expect to spend 2 to 4 hours on the job, and plan on using a quality replacement part to avoid future failures.

Why Your 2004 Chrysler 300M Fuel Pump Fails

The 2004 Chrysler 300M is equipped with a 3.5-liter V6 engine that uses an in-tank electric fuel pump . The pump is a positive displacement, gerotor-type unit with a permanent magnet electric motor . It draws fuel through a strainer and pushes it through the motor to the outlet . Over time, the pump's internal components wear out, the check valve fails, or the strainer becomes clogged with debris from the fuel tank.

Common symptoms of a failing fuel pump include:

  • Engine cranks but won't start – This is the most obvious sign. If you hear the fuel pump prime for one second when you turn the key to the ON position, it is working. If you hear nothing, the pump may be dead .
  • Sputtering or hesitation at highway speeds – A weak pump cannot maintain the required 58 psi (400 kPa) of fuel pressure .
  • Stalling, especially when the fuel tank is low – The pump relies on fuel for cooling and lubrication. Running low on fuel frequently shortens pump life.
  • Loss of power under load or uphill – The engine demands more fuel, and a failing pump cannot keep up.

The fuel pump relay, located in the Power Distribution Center (PDC), supplies battery voltage to the pump . The Powertrain Control Module (PCM) controls the relay ground circuit. If the crankshaft position sensor does not detect engine rotation, the PCM de-energizes the relay after about one second . This is normal and does not indicate a pump failure.

Where the Fuel Pump Is Located

On the 2004 Chrysler 300M, the fuel pump module is suspended inside the fuel tank . The fuel tank is located under the rear of the vehicle, behind the rear axle. The fuel pump module contains the following components:

  • Electric fuel pump – The actual pumping unit
  • Fuel level sending unit – Float and resistor that tells the gas gauge how much fuel is left
  • Inlet strainer – A mesh sock that filters large particles before they enter the pump
  • Fuel pressure regulator – Maintains system pressure at approximately 58 psi (400 kPa)
  • Fuel reservoir – A small bucket that keeps the pump submerged even when the tank is low

The fuel pump module is held in place by a lock ring that screws into the top of the fuel tank . A special tool (Chrysler number 6856) is required to remove and tighten this lock ring to 55 N·m (40.5 ft. lbs.) .

Tools and Parts You Will Need

Before starting the job, gather the following items:

Tools:

  • Floor jack and jack stands (or a transmission stand for the fuel tank)
  • Socket set with extensions (metric and SAE)
  • Flathead screwdriver
  • Special tool #6856 (fuel pump lock ring wrench) or a suitable equivalent
  • Quick-connect fuel line disconnect tool (plastic or metal)
  • Safety glasses and mechanic's gloves
  • Fire extinguisher (keep nearby, just in case)
  • Clean rags and a catch pan for spilled fuel

Parts:

  • New fuel pump module assembly (complete with sending unit, strainer, and regulator)
  • New O-ring seal for the fuel tank opening (always replace this)
  • New fuel tank strap bolts (if they are rusted or damaged)

Recommended fuel pump options for the 2004 Chrysler 300M 3.5L:

  • Walbro Fuel Pump Kit – Part # TU145, 50 PSI, 24 GPH, high pressure
  • Delphi Fuel Pump DFG0279 – Module assembly, includes regulator, 12V, 14A average draw
  • Bosch Fuel Pump 67667 – Module assembly, includes gasket and seal
  • TruGrade Fuel Pump D7152M – Module assembly, includes internal strainer, 50 PSI minimum pressure

Step-by-Step Fuel Pump Replacement Procedure

Step 1: Relieve Fuel System Pressure

Fuel in the system is under high pressure, approximately 58 psi . You must relieve this pressure before disconnecting any fuel lines.

  1. Locate the fuel pump relay in the Power Distribution Center (PDC) under the hood. The PDC is on the left side of the engine compartment .
  2. Remove the fuel pump relay from the PDC.
  3. Start the engine and let it run until it stalls from lack of fuel. This usually takes about 10 to 15 seconds.
  4. Crank the engine for another 3 seconds to ensure all pressure is released.
  5. Turn the ignition switch to the OFF position.
  6. Reinstall the fuel pump relay.

Note: The fuel pump module contains a check valve that maintains fuel volume in the rail and lines, but not pressure . After the engine cools down, fuel pressure will drop to zero.

Step 2: Disconnect the Battery

Disconnect the negative battery cable to prevent any accidental sparks or electrical shorts while working near fuel.

Step 3: Drain the Fuel Tank (Partially)

You do not need to completely drain the tank, but removing as much fuel as possible makes the job easier and safer. The fuel pump module reservoir does not empty when the tank is drained, so expect some fuel to spill when you remove the module .

Use a hand siphon pump to drain fuel into an approved gas can. If possible, drain the tank to less than 1/4 full.

Step 4: Raise and Support the Vehicle

If you plan to drop the fuel tank, you need to raise the vehicle. Use a floor jack and place jack stands at the rear jacking points. Never work under a vehicle supported only by a jack.

Important: Some Chrysler 300M models have an access panel under the rear seat cushion that allows you to reach the fuel pump without dropping the tank. Check your vehicle first. If you have an access panel, you can skip dropping the tank. If not, proceed to Step 5.

Step 5: Access the Fuel Tank (If Dropping the Tank)

  1. Remove the rear wheels and tires for better access to the fuel tank straps.
  2. Support the fuel tank with a transmission stand or a floor jack with a block of wood to distribute the load.
  3. Remove the fuel filler tube clamp and disconnect the filler neck from the tank.
  4. Disconnect the fuel pump electrical connector. The connector is located on top of the fuel pump module. Slide the connector lock to unlock, then push down on the connector retainer and pull it off .
  5. Disconnect the fuel supply line from the fuel pump module. Depress the quick-connect retainers with your thumb and forefinger .
  6. Remove the fuel tank straps. There are two straps that hold the tank in place.
  7. Slowly lower the tank a few inches, being careful not to damage the vent lines or other hoses.
  8. Disconnect the purge and vent lines from the top of the tank.
  9. Lower the tank completely and slide it out from under the vehicle.

Step 6: Remove the Old Fuel Pump Module

  1. Place the fuel tank on a clean, level surface.
  2. Use special tool #6856 to remove the fuel pump module lock ring. Turn the tool counterclockwise to loosen the ring .
  3. Lift the lock ring and O-ring seal off the tank opening. Discard the old seal.
  4. Carefully lift the fuel pump module out of the tank. The module will still contain some fuel, so tilt it to drain excess fuel into the tank.
  5. Note the orientation of the fuel level float arm. You must position the new module the same way.

Step 7: Transfer the Fuel Level Sending Unit (If Needed)

If your new fuel pump module does not come with a sending unit, you need to transfer the old one.

  1. Depress the retaining tab and remove the fuel pump/level sensor connector from the bottom of the fuel pump module electrical connector .
  2. Remove the wire terminal retaining clip from the connector .
  3. Note the location of the terminals for the level sensor wires: Level Sensor Ground, Fuel Pump (–), Level Sensor Signal, and Fuel Pump (+) .
  4. Use special tool 7812 or an equivalent to push the level sensor signal and ground terminals out of the connector .
  5. Insert a screwdriver between the fuel pump module and the top of the level sensor housing. Push the level sensor down slightly .
  6. Slide the level sensor wires through the standpipe inside the fuel pump module .
  7. Slide the level sensor out of its installation channel .

Step 8: Install the New Fuel Pump Module

  1. Wipe the seal area of the tank clean.
  2. Place a new O-ring seal in position in the tank opening .
  3. If you are using a complete module assembly, you can skip the sending unit transfer steps.
  4. Position the new fuel pump module in the tank. Make sure the alignment tabs on the underside of the module flange sit in the notches on the fuel tank .
  5. Position the lock ring over the fuel pump module.
  6. Tighten the lock ring using special tool #6856 to 55 N·m (40.5 ft. lbs.) . Do not overtighten, as this can cause a leak.

Step 9: Reinstall the Fuel Tank

  1. Raise the fuel tank on the transmission stand or floor jack.
  2. Install the fuel pump electrical connector into the hole in the body .
  3. Connect the purge and vent lines.
  4. Raise the tank into position and install the tank straps.
  5. Install the fuel filler tube and tighten the clamp.
  6. Reposition the stabilizer bar and install bolts .
  7. Lower the vehicle.

Step 10: Test the System

  1. Reconnect the negative battery cable.
  2. Turn the ignition key to the ON position (do not start the engine). You should hear the fuel pump prime for about one second. If you do not hear it, check the fuel pump relay and fuse.
  3. Turn the key to the OFF position, then back to ON. Repeat this two or three times to build fuel pressure.
  4. Check for fuel leaks at the fuel pump module connections, the fuel line quick-connect fittings, and the filler neck.
  5. Start the engine. Let it idle for a few minutes and check for leaks again.
  6. Take the vehicle for a short test drive. Monitor the fuel gauge to ensure the sending unit is working correctly.

Fuel Pressure Specifications

Knowing the correct fuel pressure helps you verify the new pump is working properly.

  • Normal operating pressure: 400 kPa (58 psi) at the fuel injectors
  • Regulator adjustment range: 400 ±34 kPa (58 ±5 psi)
  • Maximum deadhead pressure: Approximately 880 kPa (130 psi)

The fuel pressure regulator is part of the fuel pump module assembly . It contains a diaphragm, calibrated springs, and a fuel return valve. When pressure exceeds the calibrated amount, the diaphragm retracts and allows excess fuel to vent back into the tank . A separate fuel return line is not used on the 2004 Chrysler 300M .

Common Mistakes to Avoid

  • Not replacing the O-ring seal – The old seal will likely leak. Always install a new one.
  • Overtightening the lock ring – The factory spec is 55 N·m (40.5 ft. lbs.). Going beyond this can crack the tank or distort the seal.
  • Bending the float arm – The fuel level sending unit has a delicate float arm. Handle it carefully during installation.
  • Forgetting to clean the tank – If the old pump failed due to debris, you should clean the inside of the fuel tank before installing the new module.
  • Running the pump dry – Never run the engine with an empty fuel tank. The pump relies on fuel for cooling and lubrication.
  • Using the wrong fuel line disconnect tool – Using pliers or a screwdriver on plastic quick-connect fittings can damage them. Use the proper plastic or metal disconnect tool.

When to Replace the Fuel Pump Relay and Fuse

If the new pump does not work, the problem may be electrical. The fuel pump relay is located in the Power Distribution Center (PDC) on the left side of the engine compartment . The inside top of the PDC cover has a label showing the relay and fuse locations .

The fuel pump relay power circuit contains a fuse between the buss bar in the PDC and the relay . Check this fuse first. If the fuse is blown, replace it with the correct amperage rating. If the relay is faulty, replace it with an OEM equivalent.

Related Components That May Need Attention

While you have the fuel pump module out, consider inspecting or replacing these related parts:

  • Fuel injectors – If the injectors are clogged, they may need cleaning or replacement. The 2.7L and 3.5L engines use different injector and fuel rail configurations .
  • Fuel pressure regulator – On the 2004 Chrysler 300M, the pressure regulator is part of the fuel pump module . If you replace the module, the regulator is automatically replaced.
  • Fuel tank vent lines – Cracked or clogged vent lines can cause vacuum issues in the fuel system.
  • Fuel filler neck hose – Check for cracks or dry rot.

Where to Buy a Quality Replacement Fuel Pump

When it comes time to buy a replacement fuel pump for your 2004 Chrysler 300M, you want a part that is reliable, built to OEM specifications, and backed by a solid warranty. That is exactly what you get with KEMSO Fuel Pumps.

KEMSO Fuel Pumps are high-performance, OEM replacement units designed to meet or exceed the original equipment specifications for your vehicle. Each KEMSO fuel pump is built with quality components and undergoes strict testing to ensure reliable fuel delivery. The best part? Every KEMSO fuel pump comes with a lifetime warranty for total peace of mind. If your KEMSO pump ever fails due to a manufacturing defect, you get a replacement at no cost. This warranty covers a wide range of vehicles, including cars, trucks, motorcycles, ATVs, UTVs, and personal watercraft. It shows that KEMSO stands behind their product quality and is committed to customer satisfaction.

KEMSO fuel pumps are priced at a reasonable $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. Whether you are replacing the fuel pump on your 2004 Chrysler 300M or any other vehicle, KEMSO has you covered.

Visit the KEMSO website today to see the full selection of fuel pumps for your vehicle. They have a complete catalog with detailed fitment information, customer reviews, and technical support. Their online store is easy to navigate, and you can order directly with confidence.

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