Bosch 044 Fuel Pump Fittings: The Complete Guide to Choosing the Right Connections

 

If you are working on a high-performance fuel system, the Bosch 044 fuel pump is one of the most reliable and popular choices on the market. However, the key to a successful installation is choosing the correct fittings. The Bosch 044 uses threaded ports: a female M18 x 1.5 inlet and a M12 x 1.5 outlet. To connect these to your fuel lines, you will need specific adapters, banjo fittings, or barbed connectors. This guide will walk you through everything you need to know about Bosch 044 fuel pump fittings, from the types available to installation tips, and why using high-quality parts matters for your engine's performance and longevity.

What Makes the Bosch 044 Unique?

The Bosch 044 (also known as the FP200) is a high-output, roller vane fuel pump originally used as original equipment on many European cars. It has become a standard in motorsport and high-performance street applications. The pump delivers over 200 liters per hour at 5 bar (72 psi) and can support up to 685 horsepower. It is compatible with gasoline and E85, and can be installed either inside a fuel cell (submersible) or externally along the fuel line.

The pump's body features two threaded ports:

  • Inlet: M18 x 1.5 female thread
  • Outlet: M12 x 1.5 female thread

These metric threads are not directly compatible with standard American -AN fittings or push-on barbed hoses, which is why you need the correct adapter fittings.

Types of Bosch 044 Fuel Pump Fittings

There are several common ways to connect the Bosch 044 to your fuel system. Your choice depends on the type of fuel lines you are using (rubber hose, -AN braided line, or hard line) and whether you are mounting the pump inside or outside the tank.

1. Barbed Fittings for Push-On Hose

If you are using standard rubber fuel hose (e.g., 5/16" or 3/8" ID), you will need a metric male to barb adapter. These fittings screw directly into the pump's inlet or outlet and provide a barbed end for clamping a rubber hose. Common sizes include:

  • M12 x 1.5 to 5/16" barb (for outlet)
  • M12 x 1.5 to 3/8" barb (for outlet)
  • M18 x 1.5 to 1/2" barb (for inlet)
  • M18 x 1.5 to 3/4" barb (for inlet)

These barbed fittings require a hose clamp to secure the rubber hose. Always use a fuel-rated clamp and hose to prevent leaks.

2. -AN Male to Metric Male Adapters

For those using -AN braided hose (a common choice in racing and high-performance builds), you need an adapter that converts the metric thread to an -AN male thread. Then you can attach a standard -AN female hose end. Available options include:

  • M12 x 1.5 to -6AN (outlet)
  • M12 x 1.5 to -8AN (outlet)
  • M18 x 1.5 to -6AN (inlet)
  • M18 x 1.5 to -8AN (inlet)
  • M18 x 1.5 to -10AN (inlet)
  • M18 x 1.5 to -12AN (inlet)

This setup is ideal for high-flow applications because -AN fittings provide a secure, leak-free connection and allow for easy disassembly.

3. Banjo Fittings

The Bosch 044 comes with an external check valve that uses a banjo bolt connection. This is the original equipment style. You can use banjo male -AN fittings that bolt directly onto the pump's port. The banjo fitting has a hollow bolt that allows fuel to flow through, and it connects to an -AN hose end. Options include:

  • M12 banjo to -6AN (outlet)
  • M12 banjo to -8AN (outlet)
  • M18 banjo to -6AN (inlet)
  • M18 banjo to -8AN (inlet)
  • M18 banjo to -10AN (inlet)

Banjo fittings are compact and often used in tight spaces, but they may slightly restrict flow compared to a straight adapter. If you remove the check valve, you can use a standard adapter instead.

How to Choose the Right Fittings for Your Build

Selecting the right fittings depends on three main factors: flow requirements, hose type, and space constraints.

Flow Requirements: For high-horsepower applications (above 500 hp), you want to minimize restrictions. A larger inlet line helps prevent cavitation and ensures the pump is fed with adequate volume. For the inlet side, it is common to use -8AN or -10AN fittings.

Hose Type: If you are already using rubber hose, stick with barbed fittings. If you are building a high-performance system with braided stainless lines, go with -AN adapters.

Space Constraints: Banjo fittings are compact and work well in tight engine bays, but if you have room, a straight adapter provides better flow.

Installation Tips for a Leak-Free System

Use a Crush Washer: Because the Bosch 044 pump body uses a flat face for sealing, you must use a copper crush washer or a Dowty seal (bonded washer) between the pump and the adapter fitting to prevent leaks.

Avoid Over-Tightening: Over-tightening can strip the threads or damage the pump housing. Hand-thread the fitting into the pump port until snug, then use a wrench to tighten it an additional 1/4 to 1/2 turn.

Use Proper Sealant: For NPT (tapered) fittings, use a liquid or paste-type PTFE thread sealant rated for gasoline and ethanol. Apply it to the male threads only, leaving the first two threads bare to prevent sealant from entering the fuel system.

Test Before Final Assembly: After installation, perform a pressure test to check for leaks. Use a soapy water solution around the fittings and look for bubbles under pressure.

Common Mistakes to Avoid

Mixing Thread Types: Do not try to force an NPT fitting into a metric port. The threads are completely different and will not seal properly.

Using the Wrong Material: For ethanol-blended fuels like E85, avoid brass fittings. Ethanol can be corrosive to the zinc in some brass alloys over time. Anodized aluminum or stainless steel are much safer and more durable choices.

Ignoring the Check Valve: The check valve on a Bosch 044 is typically screwed into the outlet side (M12 x 1.5). If you plan to remove it, make sure your system still has a check valve elsewhere to prevent fuel from draining back to the tank.

Why Quality Matters

Using cheap or incorrect fittings can lead to fuel leaks, pressure drops, and even engine failure. High-quality fittings are made from materials that resist corrosion from modern fuels, especially ethanol blends. Stainless steel, particularly 316-grade, stands out for its corrosion resistance in harsh environments. Anodized aluminum is lightweight and cost-effective, but must be properly coated to handle ethanol.

Recommended Product: KEMSO Fuel Pump

If you are looking for a reliable replacement or upgrade, consider the KEMSO Fuel Pump. KEMSO offers high-performance fuel pumps that are designed as OEM replacements, ensuring a perfect fit for your vehicle. Their products come with a lifetime warranty, giving you peace of mind on every installation. Whether you need a pump for a car, motorcycle, ATV, or personal watercraft, KEMSO has a solution that meets your needs. Visit their website at https://www.kemsoracing.com/ to explore their full line of fuel pumps and accessories.

Final Thoughts

Choosing the right Bosch 044 fuel pump fittings is not complicated once you understand the basic thread sizes and connection types. Always match the fitting to your hose type, use the correct sealant or crush washer, and avoid over-tightening. With the right setup, your Bosch 044 fuel pump will deliver reliable performance for years to come.

For high-quality fuel pumps and fittings, check out https://www.kemsoracing.com/ for parts that are built to last and backed by a lifetime warranty.


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