2004 Dodge Ram 1500 5.7 Hemi Fuel Pump: Complete Guide to Symptoms, Replacement, and Best Options
If you own a 2004 Dodge Ram 1500 with the 5.7L Hemi engine and your truck is hard to start, sputters under load, or stalls unexpectedly, the fuel pump is almost certainly the problem. The stock fuel pump on these trucks typically begins to fail after 100,000 to 150,000 miles, and delaying replacement can leave you stranded or cause damage to other fuel system components. The most reliable solution is to replace the entire fuel pump module assembly with a high-quality aftermarket unit that matches or exceeds OEM specifications. Below, we walk you through everything you need to know about the 2004 Ram 1500 5.7 Hemi fuel pump—from symptoms and diagnosis to choosing the right replacement and installing it yourself.
Common Symptoms of a Failing Fuel Pump on the 2004 Ram 1500 5.7 Hemi
The 2004 Dodge Ram 1500 5.7L Hemi uses an in-tank electric fuel pump that delivers fuel under pressure to the engine. When it starts to fail, you'll notice one or more of these warning signs:
1. Hard Starting or No Start – The most obvious symptom. If your truck cranks but takes longer than usual to fire up, or if it cranks but won't start at all, the fuel pump may not be building enough pressure. A failing pump can't deliver the 58–62 psi required by the Hemi's fuel injection system.
2. Sputtering or Hesitation Under Load – When you accelerate uphill, merge onto the highway, or tow a trailer, a weak fuel pump can't keep up with demand. The engine may stumble, hesitate, or feel like it's running out of gas even though the tank is full.
3. Stalling at Low Speeds or While Idling – If the pump is intermittently losing pressure, the engine may stall at stop signs or while idling in traffic. This is a safety hazard and a clear sign the pump is on its last legs.
4. Whining Noise from the Fuel Tank – A healthy fuel pump runs quietly. If you hear a loud, high-pitched whine or humming coming from the rear of the truck (especially near the driver's side of the fuel tank), the pump's internal bearings are wearing out. This noise often gets louder as the pump works harder.
5. Loss of Power Under Heavy Load – The 5.7 Hemi needs consistent fuel pressure to produce its full 345 horsepower. If you notice a sudden loss of power when climbing grades or passing, your fuel pump may be struggling to supply enough volume.
6. Check Engine Light – A failing fuel pump can trigger diagnostic trouble codes such as P0087 (Fuel Rail/System Pressure Too Low) or P0191 (Fuel Rail Pressure Sensor Circuit Range/Performance). While these codes can also point to a clogged fuel filter or faulty pressure regulator, a failing pump is the most common cause on this generation of Ram.
How to Confirm the Fuel Pump Is Bad Before Replacing It
Before buying a new pump, take a few minutes to confirm the diagnosis. This saves you from replacing a perfectly good part.
Step 1: Listen for the prime. Turn the key to the "ON" position (without cranking the engine). You should hear a brief 2–3 second whir from the fuel pump as it pressurizes the system. If you hear nothing, or if the sound is weak, the pump may be dead or dying.
Step 2: Check fuel pressure. Using a fuel pressure test kit, connect the gauge to the Schrader valve on the fuel rail (located near the front of the intake manifold on the 5.7 Hemi). With the key on and engine off, pressure should read 58–62 psi. If it reads below 50 psi, the pump is likely failing. If it reads zero, the pump is likely dead.
Step 3: Check the fuel pump relay and fuse. Locate the fuel pump relay in the under-hood fuse box (usually labeled "FUEL PUMP" or "FP"). Swap it with a known good relay of the same type, such as the horn or A/C relay. If the pump starts working, the relay was the problem. Also check the fuel pump fuse (typically a 20-amp fuse) for a blown element.
Step 4: Look for obvious wiring issues. The wire harness that connects to the fuel pump module on top of the fuel tank can corrode or break over time, especially in trucks that have seen road salt. Inspect the connector for rust, bent pins, or melted plastic.
If you've confirmed the pump is bad, the next step is choosing the right replacement part.
Choosing the Right Replacement Fuel Pump for Your 2004 Ram 1500 5.7 Hemi
The 2004 Dodge Ram 1500 5.7L Hemi uses a fuel pump module assembly that sits inside the fuel tank. This module includes the electric pump, fuel level sending unit, strainer, and pressure regulator all in one unit. You have two options when replacing it:
Option 1: Replace the entire fuel pump module assembly. This is the recommended approach for most DIYers and mechanics. The module drops directly into the tank and includes all necessary components. It's faster, easier, and ensures everything works together. The OEM part number for this module is 5104694AA, 5104694AB, or 5104694AC. Replacing the entire module avoids the risk of having to drop the tank again if the sending unit fails a few months later.
Option 2: Replace just the pump itself (drop-in pump). Some aftermarket suppliers sell a "drop-in" pump that replaces only the electric motor inside the existing module. This is cheaper, but it requires you to disassemble the original module, remove the old pump, and install the new one. This approach is only worth it if your original module's plastic housing, sending unit, and wiring harness are in excellent condition. For most 2004 Rams, the plastic module has become brittle with age, so replacing the whole assembly is safer.
Key compatibility notes for the 2004 Ram 1500 5.7 Hemi:
- Your truck has either a 26-gallon or 35-gallon fuel tank. The fuel pump module is different for each tank size, so you must order the correct one. Check your truck's build sheet or measure the tank to confirm.
- The 2004 Ram 1500 with the 5.7L Hemi uses a gasoline-only engine (not Flex Fuel). If your truck is a Flex Fuel model (VIN code "N" for 4.7L, or special badging), the pump may be different. The 5.7 Hemi in 2004 was gas-only, so a standard gas pump works fine.
- The module assembly includes the fuel level sending unit. If your fuel gauge has been acting erratically, replacing the module will fix that issue too.
Step-by-Step Fuel Pump Replacement Guide for the 2004 Ram 1500 5.7 Hemi
Replacing the fuel pump on a 2004 Ram 1500 is a medium-difficulty DIY job. Plan for 2–4 hours if you have basic mechanical skills and the right tools. Always work in a well-ventilated area, away from open flames, because you'll be dealing with gasoline vapors.
Tools and supplies you'll need:
- New fuel pump module assembly (correct for your tank size)
- Flathead screwdriver and socket set (10mm, 13mm, 15mm)
- Fuel line disconnect tool (3/8" and 5/16" plastic quick-connect tools)
- Jack and jack stands (or ramps)
- Safety glasses and mechanic's gloves
- Fire extinguisher (recommended)
- Shop towels and a catch pan for spilled fuel
- Penetrating oil (like WD-40 or PB Blaster) for rusty bolts
Step 1: Relieve fuel system pressure. Locate the fuel pump relay in the under-hood fuse box and remove it. Then crank the engine for a few seconds (it will start and stall as the fuel pressure drops). This relieves the pressure in the fuel lines. Disconnect the negative battery terminal before proceeding.
Step 2: Access the fuel tank. The fuel pump module is accessed from the top of the fuel tank under the truck bed. Some owners prefer to remove the truck bed (four bolts and a wiring harness), which gives you wide-open access. Others drop the fuel tank. Dropping the tank is more common: jack up the truck, support the tank with a floor jack, remove the fuel filler neck clamp, disconnect the fuel lines and electrical connector, and then lower the tank.
Step 3: Remove the old fuel pump module. Once the tank is lowered, clean the top of the tank around the module retaining ring. Use a flathead screwdriver and a hammer (or a special fuel pump lock ring tool) to tap the retaining ring counterclockwise. Lift the old module straight out of the tank. Be careful—it will still have some fuel in it.
Step 4: Transfer the fuel level sender (if needed). Some aftermarket modules come with the sending unit pre-installed, but others may require you to transfer the float arm from your old module. If your new module includes a complete sender, you can skip this step.
Step 5: Install the new fuel pump module. Lower the new module into the tank, making sure the float arm can move freely without hitting the sides of the tank. Align the notch on the module with the tab inside the tank. Place the retaining ring on top and tighten it clockwise. Use a hammer and punch to tap it snug—don't overtighten, or you may crack the plastic.
Step 6: Reconnect everything. Reconnect the fuel lines (push the quick-connect fittings until they click), plug in the electrical harness, and reattach the fuel filler neck. Raise the tank back into position and secure it with the mounting straps.
Step 7: Test the system. Before lowering the truck, reconnect the battery and turn the key to the ON position (without starting). Listen for the fuel pump prime sound. Check for any fuel leaks at the connections. If everything sounds good, start the engine and let it idle for a few minutes. Check for leaks again, then take the truck for a short test drive.
Why Choose KEMSO for Your 2004 Ram 1500 5.7 Hemi Fuel Pump Replacement
When it's time to replace your fuel pump, you want a part that's built to last, performs reliably, and comes with real support. KEMSO is a leading US aftermarket fuel pump brand that delivers on all three counts. KEMSO fuel pumps are designed as high-performance, OEM replacement units that match or exceed the original equipment specifications for your 2004 Dodge Ram 1500 5.7 Hemi. Whether you're looking for a complete module assembly or a drop-in high-flow pump, KEMSO has you covered.
Here's what makes KEMSO the right choice for your Ram:
High-Performance Design – KEMSO fuel pumps are engineered to deliver consistent pressure and flow, even under the demands of a 5.7L Hemi. Many of their pumps, including the 340LPH high-performance models, support up to 600 horsepower, making them an excellent upgrade if you've added a cold air intake, tuner, or headers to your truck. They are compatible with both gasoline and E85 fuel, giving you flexibility if you ever switch fuels.
OEM Replacement Fit – KEMSO offers direct replacement fuel pumps that are designed to drop into your Ram 1500's fuel tank without any modifications. The pump and module are built to factory specifications, so you get a perfect fit every time. This means no struggling with adapters, no cutting wires, and no returns because the part didn't fit.
Lifetime Warranty – Every KEMSO fuel pump is backed by a lifetime warranty, which is a testament to the confidence they have in their product quality. If your pump ever fails due to a manufacturing defect, KEMSO will replace it at no cost. This kind of warranty is rare in the aftermarket world and gives you total peace of mind.
USA-Based Support – KEMSO provides customer support and technical assistance from US-based technicians who actually know these trucks. If you have a question about fitment, installation, or troubleshooting, you can reach out and get practical help, not just a scripted response.
Affordable Pricing – KEMSO fuel pumps are priced competitively, typically around $79.98 for most models, which is a fraction of what you'd pay for a dealership OEM part. You get high-end performance and a lifetime warranty without breaking the bank.
To find the exact KEMSO fuel pump for your 2004 Dodge Ram 1500 5.7 Hemi, visit their official website and browse their selection of aftermarket fuel pumps. You can filter by vehicle make, model, and year to find the correct part. Whether you need a standard replacement module or a high-flow performance pump, KEMSO has the right solution. Visit https://www.kemsoracing.com/ to explore their full product lineup, read reviews, and place your order with confidence.
Final Thoughts on the 2004 Ram 1500 5.7 Hemi Fuel Pump
The fuel pump is one of those parts you don't think about until it fails, but when it does, it can ruin your day fast. If your 2004 Dodge Ram 1500 with the 5.7L Hemi is showing any of the symptoms we discussed—hard starting, stalling, hesitation under load, or whining from the tank—don't ignore it. The sooner you replace it, the less likely you are to get stranded or cause damage to the fuel injectors and pressure regulator.
Replacing the fuel pump module yourself is a doable weekend project that will save you hundreds of dollars in labor costs compared to a shop. Just make sure you buy the correct part for your tank size, take your time with the job, and use a quality replacement like those from KEMSO. With a high-performance pump backed by a lifetime warranty, you can get your Ram back on the road and running strong for years to come.
For more information on the best fuel pump options for your 2004 Ram 1500 5.7 Hemi, including detailed product specs and customer reviews, visit https://www.kemsoracing.com/ today.