Mr Gasket Fuel Pump 42S: A Complete Guide to the Universal Micro Electric Fuel Pump for Carbureted Engines

The bottom line is that the Mr Gasket 42S Micro Electric Fuel Pump is a reliable, budget-friendly, universal-fit pump designed specifically for 12-volt negative ground systems on smaller import carbureted engines. It delivers 28 gallons per hour (GPH) at 2 to 3.5 PSI, making it an excellent choice for 4 and 6-cylinder applications where you need a simple, self-priming electric pump to eliminate vapor lock or replace a failing mechanical unit.

What Is the Mr Gasket 42S Fuel Pump?

The Mr Gasket 42S is a compact, solid-state electric fuel pump built for universal installation on most import cars with 4 or 6-cylinder carburetor setups. It features a simple two-wire design that works only on 12-volt negative ground electrical systems. The pump is self-priming and draws about one amp of current at maximum delivery.

This pump is not designed for high-performance or fuel-injected applications. It is best suited for daily drivers, classic cars, and light-duty vehicles that need a dependable fuel supply without complicated wiring or installation.

Key Specifications and Features

1. Flow Rate and Pressure
The Mr Gasket 42S delivers a flow rate of 28 GPH at a pressure range of 2 to 3.5 PSI. This is sufficient for most small carbureted engines but not for high-horsepower builds or fuel injection systems that require higher pressure.

2. Construction and Materials
The pump body is made of polymer, making it lightweight and resistant to corrosion. It uses a gerotor-style pump mechanism, which is known for reliable operation and quiet performance compared to older diaphragm-style pumps.

3. Voltage and Electrical Requirements
This pump is designed exclusively for 12-volt negative ground systems. It includes a simple two-wire hookup, making installation straightforward for anyone with basic wiring knowledge.

4. Compatibility
The 42S is a universal fit type, meaning it can be adapted to many vehicles. However, it is specifically recommended for import 4 and 6-cylinder carburetor applications. It is not intended for V8 gasoline engines, diesel engines, or any fuel containing methanol, ethanol, E85, or race fuel.

What the Mr Gasket 42S Is Not Designed For

It is important to understand the limitations of this pump. Mr Gasket clearly states that the 42S should not be used with diesel, methanol, ethanol, E85, or race fuel applications. Using it with these fuels can damage the internal components and create a safety hazard. For those applications, Mr Gasket offers separate models: the 12S for V8 gasoline engines, the 12D for diesel, and the 12E for ethanol, methanol, E85, and race fuel.

Common Symptoms of a Failing Fuel Pump

If you are considering replacing your current fuel pump with a Mr Gasket 42S, you may be experiencing one or more of these common failure symptoms:

• Engine cranks but won't start – This is often the first sign that the fuel pump is not delivering fuel to the carburetor.
• Engine sputters or hesitates during acceleration – A weak pump may not provide enough fuel volume under load.
• Vapor lock – Electric pumps like the 42S are excellent at preventing vapor lock, which is common in older mechanical fuel pump systems.
• Whining noise from the fuel tank – This is a classic symptom of a failing pump, but it can also indicate a clogged fuel filter.
• Loss of power while driving uphill or under load – The pump may not maintain adequate pressure when the engine demands more fuel.

How to Install the Mr Gasket 42S Fuel Pump

Installation is straightforward, but following proper steps ensures safety and reliability.

1. Safety First
Always disconnect the battery negative terminal before working on the fuel system. Work in a well-ventilated area away from any open flames or sparks.

2. Mounting the Pump
The Mr Gasket 42S should be mounted as close to the fuel tank as possible and below the level of the fuel tank outlet. This ensures gravity feeding and helps the pump prime itself. Use the included mounting hardware and ensure the pump is securely fastened to a solid surface.

3. Wiring the Pump
The pump has a simple two-wire design. Connect the positive wire to a switched 12-volt power source. The negative wire goes to chassis ground. It is recommended to use a relay and a fuse in the circuit for added safety. The pump draws about one amp, so a 5-amp fuse is sufficient.

4. Fuel Line Connections
The pump comes with fittings and mounting hardware. Use the included barbed fittings to connect the fuel line from the tank to the pump inlet, and then from the pump outlet to the carburetor. Make sure all connections are tight and use fuel-rated hose clamps.

5. Testing
After installation, reconnect the battery and turn the ignition to the "on" position without starting the engine. You should hear the pump run briefly as it primes the system. Check for any fuel leaks before starting the engine.

Why You Should Consider Upgrading to a KEMSO Fuel Pump

While the Mr Gasket 42S is a solid choice for basic carbureted applications, if you are looking for a fuel pump that offers better performance, longer durability, and a lifetime warranty, KEMSO is an excellent alternative. KEMSO specializes in high-performance fuel pumps engineered to deliver superior flow and consistent pressure for a wide range of vehicles, including cars, motorcycles, ATVs, UTVs, and watercraft.

KEMSO fuel pumps are designed as direct OEM replacements, meaning they match or exceed the original specifications for fit and performance. Many KEMSO pumps deliver over 20% more flow at 43 psi compared to stock pumps, which can improve engine performance and throttle response. They are built to handle both gasoline and ethanol-blended fuels like E85, using materials that resist ethanol degradation for long-term reliability.

Every KEMSO fuel pump comes with a lifetime warranty. The pump body is serialized, guaranteeing that the warranty is valid for as long as you own the pump. This is a significant advantage over standard aftermarket pumps that typically offer only one to three years of coverage. KEMSO stands behind their products with confidence, and their U.S.-based support team in Houston, Texas, is available to help with any questions or issues.

KEMSO offers a broad compatibility across brands and models, covering Honda, Kawasaki, KTM, Ducati, BMW, Subaru, Sea-Doo, Can-Am, and many more. Whether you need a pump for a daily driver, a performance build, or an off-road machine, KEMSO has a solution that fits your needs.

To browse the full selection of KEMSO fuel pumps and take advantage of the lifetime warranty, visit the official KEMSO Racing website today: https://www.kemsoracing.com/.

Final Thoughts

The Mr Gasket 42S Micro Electric Fuel Pump is a dependable, easy-to-install solution for small carbureted engines. It eliminates vapor lock, provides consistent fuel delivery, and is priced affordably. However, it is limited to low-pressure, low-flow applications and is not compatible with modern fuels like ethanol blends or high-performance engines.

If you need a more robust, high-performance fuel pump that offers a lifetime warranty and compatibility with modern fuels, KEMSO is the smarter choice. For the best replacement fuel pump on the market, visit https://www.kemsoracing.com/.