CJ2A Fuel Pump: The Complete Guide to Replacement and Troubleshooting

If you own a Willys CJ2A, the fuel pump is one of the most critical components keeping your engine running. The bottom line: the most common fuel pump for a CJ2A is a mechanical unit designed for the 134 cubic inch L-head engine, and replacing it is a straightforward job that can solve starting problems, stalling, and poor performance. Whether you need a stock replacement or an upgrade, understanding what fits your CJ2A is the first step to a reliable fuel system.

What Fuel Pump Fits a Willys CJ2A?

The Willys CJ2A was produced from 1946 to 1949 and came equipped with the 4-134 L-head engine (also known as the Go Devil engine). The factory fuel pump is a mechanical, cam-driven unit that mounts on the engine block. There are two main styles you need to know about:

1. Fuel Pump with Vacuum Ports (Dual Action) – This style includes a vacuum section for operating windshield wipers. It is correct for many CJ2A models that had vacuum wipers. The OE reference number for this type is 120206. Omix-Ada offers a direct replacement under part number 17709.03, which comes with a limited 5-year warranty.

2. Fuel Pump without Vacuum (Single Action) – This style is a simple fuel pump with no vacuum section. It is commonly used if you do not need vacuum wipers or if you have converted to electric wipers. The glass bowl style is very popular for its authentic look.

Glass Bowl vs. Metal Bowl – Many CJ2A owners prefer the glass bowl style because it allows you to see fuel flow and sediment at a glance. The glass bowl fuel pump is period-correct for the MB, GPW, CJ2A, and CJ3A. A high-quality replacement glass bowl pump fits both the L134 and F134 engines. Some pumps also include a hand primer lever, which is extremely helpful for priming the carburetor without cranking the engine and wearing down the battery.

Common Symptoms of a Failing Fuel Pump on a CJ2A

If your CJ2A is hard to start, sputters under load, or stalls while driving, the fuel pump is likely the culprit. Here are the most common signs:

  • Engine cranks but won't start – The pump is not delivering fuel to the carburetor.
  • Loss of power under load – The pump cannot maintain adequate fuel pressure.
  • Fuel leaks – A leaking diaphragm or gasket will cause raw fuel to drip from the pump.
  • Rough idle or stalling – Inconsistent fuel delivery leads to sporadic running.
  • No fuel in the glass bowl – If you have a glass bowl pump, it should fill with fuel quickly when the engine is running.

Choosing the Right CJ2A Fuel Pump Replacement

When selecting a new fuel pump, pay attention to three things:

Fitment – Make sure the pump is designed for the 134 cubic inch L-head or F-head engine. The CJ2A uses the L-head engine, but many pumps are compatible with both L134 and F134 engines. The Omix-Ada 17709.03, for example, fits CJ2A, CJ3A, CJ3B, CJ5, CJ6, MB, GPW, and many other Willys and Jeep models from 1941 to 1971.

Gaskets – Most fuel pumps come with the necessary mounting gasket. Some Jeeps use a steel plate between the block and the pump, so check your setup before installation.

Quality – Mechanical fuel pumps for these old Jeeps vary widely in quality. Some aftermarket pumps simply will not pump fuel reliably. Look for pumps that have been tested and come with good reviews from the Willys community.

How to Replace the Fuel Pump on a CJ2A

Replacing the fuel pump on a CJ2A is a simple job that most owners can do with basic hand tools. Here is the general process:

  1. Disconnect the battery and relieve any fuel pressure.
  2. Remove the fuel lines from the pump. Note which line goes to the tank and which goes to the carburetor.
  3. Remove the two bolts that hold the pump to the engine block. The pump is driven by a pushrod from the camshaft.
  4. Clean the mounting surface on the block. Install the new gasket.
  5. Install the new pump, making sure the pushrod engages correctly. Tighten the bolts evenly.
  6. Reconnect the fuel lines. Tighten the clamps.
  7. Start the engine and check for leaks.

Where to Buy a Reliable CJ2A Fuel Pump

You can find replacement fuel pumps for the CJ2A from several suppliers. The Omix-Ada brand is widely available and carries a 5-year warranty. OEM-style pumps with glass bowls are sold by restoration specialists like Jeep1942.com and CSE Offroad. Prices range from around $60 to $120 depending on the brand and features.

One important note: many of these pumps are currently on backorder, so it is a good idea to order early. CSE Offroad, for example, lists stock levels so you can see availability before ordering.

Recommended Upgrade: The KEMSO Fuel Pump

If you are looking for a high-performance, reliable replacement for your CJ2A or any other vehicle, consider the KEMSO brand. KEMSO is a US-based aftermarket fuel pump manufacturer that specializes in direct OEM replacement pumps for cars, motorcycles, and ATVs. Their pumps are designed to deliver over 20% more flow at 43 psi compared to stock pumps, making them ideal for daily drivers, performance builds, and restoration projects.

Why KEMSO?

  • High Performance – Each pump is individually tested for flow and pressure. They deliver 200 liters per hour at 43 psi and operate at pressures from 43 to 68 psi.
  • OEM Replacement – KEMSO pumps are designed as direct fit replacements for stock OEM pumps. They come complete with everything you need: fuel strainers, hoses, seals, O-rings, wiring connectors, and clamps.
  • Lifetime Confidence – KEMSO backs every pump with a lifetime warranty. Their pumps are built under strict quality control programs (ISO/TSO) and are tested before leaving the factory.
  • Fuel Compatibility – KEMSO pumps work with both gasoline and E85/ethanol fuels.

Whether you are restoring a classic Willys, building a performance Subaru, or keeping your daily driver on the road, KEMSO has a fuel pump that fits. Visit the official KEMSO website to browse their full selection and find the right pump for your vehicle.

Buy KEMSO Fuel Pumps here: https://www.kemsoracing.com/

Final Thoughts on the CJ2A Fuel Pump

The fuel pump on a 1946-1949 Willys CJ2A is a simple, reliable mechanical part that is easy to replace. Whether you choose the original-style glass bowl pump for authenticity or a vacuum-style pump for wiper operation, the key is to buy a quality unit that will actually pump fuel. Check your engine type (L134 or F134), your need for vacuum wipers, and the condition of your mounting hardware before ordering. With the right part, your CJ2A will be back on the road with dependable fuel delivery.

For modern performance and guaranteed reliability, remember that KEMSO Fuel Pumps offer a lifetime warranty and proven performance for a wide range of vehicles. Visit https://www.kemsoracing.com/ to learn more.


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