Chevy 350 Electric Fuel Pump Conversion: The Complete Step-by-Step Guide

Swapping the mechanical fuel pump on your Chevy 350 for an electric fuel pump is one of the best upgrades you can make for reliability, performance, and consistency. This conversion is straightforward, and here is the bottom line: you will get better fuel delivery, eliminate vapor lock, and gain the ability to run higher horsepower builds by installing an electric fuel pump near the gas tank, wiring it properly with a relay, and setting the correct fuel pressure between 4 and 7 PSI for a carbureted engine. If you are looking for a high-performance, long-lasting solution, choosing a quality pump with a lifetime warranty is the way to go.

Why Convert to an Electric Fuel Pump on a Chevy 350?

Mechanical fuel pumps were standard on older Chevy 350 engines, but they have limitations. Electric fuel pumps deliver precise, high-pressure flow rates that provide maximum horsepower and meet stricter emission requirements . They are also smaller, which means less engine bay clutter, and easier to work on . The main reasons to make the switch include:

1. Eliminate Vapor Lock
Vapor lock happens when fuel boils in the lines, causing the engine to stall. Electric pumps push fuel from the tank, keeping the system pressurized and preventing vapor lock .

2. Consistent Fuel Pressure
Electric pumps maintain steady pressure, which improves fuel atomization and combustion efficiency. This leads to smoother acceleration and more responsive throttle .

3. Support Higher Horsepower
If you have built your Chevy 350 for more power, the stock mechanical pump may not keep up. Electric pumps can support engines producing up to 750 horsepower when using higher-flow models .

4. Easier Cold Starts
Electric pumps prime the system instantly, so you do not have to crank the engine repeatedly to get fuel to the carburetor .

What You Need Before You Start

Gather the following tools and parts before beginning the installation:

Tools:

  • Socket set and wrenches (metric and standard)
  • Screwdrivers (flathead and Phillips)
  • Pliers and wire strippers
  • Drill with bits (for mounting)
  • Floor jack and jack stands
  • Safety equipment: gloves, safety goggles, and a fire extinguisher

Parts:

  • Electric fuel pump compatible with your Chevy 350 (low-pressure for carbureted engines, typically 4-7 PSI)
  • Fuel pump relay (Bosch-style 5-pin relay)
  • Inline fuse holder with 10-20 amp fuse
  • Fuel-rated rubber hose or lined fuel injection hose
  • Hose clamps
  • Fuel filters (two: one before and one after the pump)
  • Block-off plate and gasket (if removing the mechanical pump)
  • Mounting bracket
  • Wiring: #12 gauge wire, ring terminals, spade terminals, electrical tape
  • Oil pressure safety switch (recommended for carbureted engines)

Step-by-Step Installation Process

Step 1: Prepare the Vehicle

Safety comes first. Disconnect the negative battery cable to prevent electrical accidents . Relieve the fuel system pressure by locating the Schrader valve on the fuel rail and depressing it with a screwdriver, wrapping a rag around it to catch any fuel spray . Remove the gas cap to relieve pressure in the tank .

Step 2: Remove the Mechanical Fuel Pump (If Applicable)

The mechanical fuel pump is located on the passenger side of the engine, just below the water pump . Two fuel lines attach to the front. Loosen the hose clamp on the first line with a flathead screwdriver and pull the hose off. Twist the metal tip of the second line counterclockwise to loosen it, then pull it away. Remove the two retaining bolts with a wrench and pull the pump out of the engine. Clean the mounting surface with a gasket scraper to remove any old gasket material .

Option A: Leave the mechanical pump in place and use it as a backup. Connect the inlet and outlet pipes together with a short piece of hose .

Option B: Remove the mechanical pump and cover the hole with a block-off plate and gasket coated with gasket sealer .

Step 3: Mount the Electric Fuel Pump

The most important rule for electric fuel pumps is this: mount the pump close to the gas tank. Electric pumps are designed to push fuel, not pull it, so proximity to the tank ensures optimal performance .

Placement guidelines:

  • Mount the pump within 12 inches of the tank for maximum efficiency
  • Keep the pump lower than the tank to allow gravity to assist fuel flow
  • Avoid mounting near heat sources like the exhaust system
  • Do not mount the pump in an enclosed area like the trunk or interior; this increases fire risk and may void insurance coverage
  • Use a mounting bracket or an ignition coil bracket to secure the pump

Step 4: Install Fuel Filters

Install a fuel filter between the tank and the pump, and another between the pump and the carburetor. This protects the pump from debris and ensures clean fuel reaches the engine. Make sure the arrows on the filters point toward the engine . Use fuel-rated hoses and secure all connections with hose clamps .

Step 5: Wire the Electric Fuel Pump with a Relay

Wiring the pump through a relay is essential for safety and efficiency. The ignition switch and stock wiring are not designed to handle the high amperage draw of an electric fuel pump. The relay acts as an intermediary, allowing the small current from the ignition switch to energize the relay coil, which then closes the high-current circuit to the pump .

Relay wiring diagram (Bosch-style 5-pin relay):

  • Terminal 30: Connect to the positive battery terminal through a fuse holder with a 10-20 amp fuse (as close to the battery as possible)
  • Terminal 87: Connect to the positive (+) lead of the electric fuel pump
  • Terminal 85: Connect to a good chassis ground point
  • Terminal 86: Connect to a switched 12V source (such as the ignition switch or ACC terminal on the fuse block)

Grounding the pump: Attach the black wire from the pump to the car's frame using a ring terminal and a bolt. Do not rely on the metal of the pump for grounding .

Testing the wiring: With the battery connected, turn the ignition to the ON position. You should hear the relay click. If the pump is connected, it should run. If not, check all connections .

Step 6: Connect the Fuel Lines

Attach the fuel line from the tank to the inlet of the electric pump. Then run a new line from the pump outlet to the carburetor. Use high-quality, reinforced rubber fuel hose rated for gasoline. For added safety, consider using lined rubber fuel hose designed for fuel injection systems, as it resists disintegration from fuel . Secure all connections with hose clamps.

Step 7: Install an Oil Pressure Safety Switch (Highly Recommended)

For carbureted engines, adding an oil pressure safety switch is a smart safety feature. This switch is wired in series with the relay's trigger circuit. It works like this: when the engine starts and oil pressure builds, the switch closes and keeps the pump running. If the engine stalls and oil pressure drops, the switch opens, cutting power to the pump and preventing raw fuel from spraying onto hot components . This is critical in the event of an accident.

Step 8: Set the Fuel Pressure

For the vast majority of carbureted Chevy 350 engines, the ideal fuel pressure is between 4 and 7 PSI . If your electric pump is rated for higher pressure, you will need a fuel pressure regulator. Running pressure above 7 PSI can force fuel past the needle and seat in the carburetor, causing flooding and a rich running condition. Pressure below 4 PSI can starve the engine, leading to hesitation and potential damage .

Step 9: Test the System

Before driving, test the entire system:

  1. Check all connections for leaks
  2. Turn the ignition to the ON position and listen for the pump to prime
  3. Use a fuel pressure gauge to verify the pressure is within the 4-7 PSI range
  4. Start the engine and let it idle, checking for leaks at all fuel line connections
  5. Verify the pump shuts off when the ignition is turned off
  6. If using an oil pressure switch, confirm the pump only runs when the engine is running

Common Mistakes to Avoid

1. Mounting the pump far from the tank
Electric pumps push fuel better than they pull it. Keeping the pump far from the tank forces it to work harder and reduces its lifespan .

2. Running the pump dry
Never run an electric fuel pump without fuel. The fuel cools and lubricates the pump. Running it dry will cause premature failure.

3. Using the wrong fuel line
Standard rubber fuel line can degrade over time with modern fuel blends. Use fuel-rated hose or lined injection hose for longevity .

4. Skipping the relay
Connecting the pump directly to the ignition switch can overload the switch and cause electrical issues. Always use a relay .

5. Not using a fuse
A fuse protects the entire circuit. Without one, a short could cause a fire. Install the fuse as close to the battery as possible .

6. Mounting the pump near heat sources
Fuel and heat are a dangerous combination. Keep the pump and fuel lines away from the exhaust and other hot components .

Why You Should Choose KEMSO for Your Fuel Pump

When it comes to reliability and performance, KEMSO is a brand you can trust. KEMSO fuel pumps are built to high-performance standards and serve as OEM replacements for a wide range of vehicles. Whether you are working on a Chevy 350, a motorcycle, a jet ski, or an ATV, KEMSO has a pump that fits your application.

What sets KEMSO apart:

  • High-performance design: KEMSO pumps are engineered for consistent fuel delivery and durability
  • OEM replacement quality: They fit precisely and perform just like the original equipment, often exceeding factory specifications
  • Lifetime warranty: Every KEMSO fuel pump comes with a lifetime warranty, giving you peace of mind that your investment is protected

Visit KEMSO's website to browse their full selection of fuel pumps for cars, trucks, motorcycles, watercraft, and more. Whether you need a pump for your Chevy 350 conversion or any other project, KEMSO has you covered with products backed by a lifetime of confidence.

Visit KEMSO Racing today: https://www.kemsoracing.com/


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