Adjusting Hilborne Fuel Pump Pressure: A Step-By-Step Guide

Hilborn fuel pumps are mechanical fuel injection systems that are popular among high-end racers, especially those using alcohol fuels. The pressure on these fuel pumps can be adjusted by changing the orifice size of the port nozzles, which regulates the amount of fuel delivered to the engine. This is done by using different-sized pills that have varying orifice sizes. The pump's safety margin allows it to supply more fuel than the engine needs, and the excess is recycled back to the gas tank. The pump's outlet has three ports, one feeding the injectors and two available to return excess fuel. The main jet or pill ensures that fuel flows to the nozzles first, and its size can be changed to control the amount of fuel returned to the tank, thereby adjusting the fuel pressure.

How to set the metering valve

Setting the metering valve is a crucial step in ensuring optimal performance of your Hilborn fuel injection system. Here is a detailed guide on how to set the metering valve:

• Set the Injector to Wide-Open Throttle: Begin by adjusting the injector to its widest throttle opening. This will allow you to access and manipulate the metering valve easily.
• Understand the Metering Valve Schematic: Refer to the Metering Valve Schematic provided by Hilborn. This schematic illustrates the relationship between the throttle shaft, the metering valve rotor, and the rod-end bearings. The distance "X" between the center of the rod-end bearings should be equal to the distance "Y" between the center of the throttle shaft and the metering valve rotor. Make sure to note the offset inlet fitting on the block, which will be important for the next step.
• Adjust the Rotor: Locate the number on the metering valve rotor. Adjust the rotor so that the number is positioned on the wide side of the offset inlet fitting. This ensures that the rotor is aligned correctly.
• Tighten the Arm: Once the rotor is in the correct position, tighten the arm that connects the rotor to the throttle shaft. Ensure that both the rotor and throttle shaft are securely fastened.
• Check Throttle Response: After setting the metering valve, test the throttle response. With the injector at wide-open throttle, observe whether the throttle has a smooth and immediate reaction. Fine-tune as needed by making small adjustments to the metering valve rotor and retesting the throttle response.
• Fine-Tuning and Testing: It is important to test the fuel injection system under various conditions, such as different engine speeds and loads. Fine-tune the metering valve as necessary to ensure optimal performance and fuel delivery across a range of operating parameters.
• Maintain Cleanliness: Throughout the process of setting the metering valve, maintain a clean work environment. Keep dirt and debris away from the fuel injection system, especially the fuel filter and nozzle, to prevent any issues with fuel flow or performance.

By following these steps and referring to the Metering Valve Schematic provided by Hilborn, you can ensure that your metering valve is set correctly. This will help optimize the performance of your Hilborn fuel injection system, providing the precise fuel delivery and throttle response needed for your vehicle's specific requirements.

Adjusting the barrel valve

Before beginning any adjustments, it is important to understand the role of the barrel valve in the fuel injection system. The barrel valve acts like a fuel shut-off valve, controlling the amount of fuel delivered to the engine during idle and transitional periods up to wide-open throttle (WOT). It works in conjunction with the secondary bypass valve to enhance part-throttle fuel control.

Now, let's get into the step-by-step process of adjusting the barrel valve:

• Start by setting the injector to wide-open throttle. Refer to the Metering Valve Schematic for the correct positioning. The distance "X" between the centre of the rod-end bearings should match the distance "Y" between the centre of the throttle shaft and the metering valve rotor. Make sure the rotor number is located on the wide side of the offset.
• Tighten the arm on the rotor and the throttle shaft securely.
• At this point, you can make fine adjustments to the barrel valve to optimise throttle response. Turn the barrel valve hex link one flat at a time. This subtle adjustment can significantly improve throttle response off-idle and eliminate any burps or bogs.
• Once you've adjusted the barrel valve, it's important to test the system's performance. Take the vehicle for a drive and evaluate the throttle response, especially during transitions from idle to WOT. Make note of any hesitations, bogging down, or lack of power.
• If you're experiencing issues with throttle response, you may need to adjust the barrel valve again in small increments. Remember, the barrel valve directly impacts fuel delivery during idle and transitional periods, so small adjustments can make a noticeable difference.
• After making any adjustments, re-test the vehicle's performance and compare it to the previous settings. It's important to keep track of your adjustments and their impact on performance.
• Additionally, consider using a tool like a Uni-Syn device or a heat gun to measure exhaust temperatures. This can provide valuable data to fine-tune the barrel valve adjustment.
• Once you're satisfied with the throttle response and overall performance, you can move on to tuning other aspects of the fuel injection system, such as the main jet and bypass valves.

Remember, adjusting the barrel valve is just one part of the overall tuning process for your Hilborn fuel injection system. Each component works together to ensure optimal fuel delivery and engine performance. Always refer to the manufacturer's guidelines and seek expert advice if you're unsure about any adjustments.

Selecting the right pump size

• Engine Size and Horsepower: The pump size should be chosen based on the engine size and horsepower requirements. For instance, the Hilborne PG150 series offers different pump sizes, with #00 being suitable for extremely small engines like motorcycles, while #0 is recommended for medium-sized engines ranging from 200" to 360".
• Fuel Type and Requirements: Consider the type of fuel used, such as gas, methanol, or nitro. The amount of nitro in the fuel can impact the pump selection. The Hilborne PG150 series offers pump sizes like #S0 and #1/2 for engines using small amounts of nitro.
• Fuel Pressure and Volume: Fuel pressure and volume requirements play a significant role in pump selection. Carbureted engines typically operate at lower pressures (4-7 psi), while modern EFI systems require higher pressures (40-60 psi). The fuel pressure affects the flow rate, with higher pressure resulting in a lower flow rate.
• Engine Specifications: Understand the specific requirements of your engine, including its maximum horsepower, fuel consumption rate, and fuel pressure needs. This information can be obtained through dyno-testing or by referring to the manufacturer's specifications.
• System-Pressure Requirements: Depending on the engine and fuel type, consider the system-pressure requirements. For example, nitrous engines may require slightly higher brake-specific fuel consumption, while forced-induction engines (supercharged or turbocharged) typically have the highest consumption rates.
• Fuel Pump Series: Hilborne offers different pump series, such as the PG150, PG175, and PG250 series. Each series caters to a specific range of engine sizes and fuel requirements. Refer to the manufacturer's guidelines to choose the appropriate series for your application.
• Fuel Pump Volume: The fuel pump volume is indicated by the first digit of the serial number stamped into the Hilborne pump castings. This information helps determine the pump's flow rate and capacity, ensuring it can deliver the required fuel volume for your engine.
• Fuel Pump Pressure: Some fuel pumps are rated based on the pressure they can produce. For example, the Walbro 255 lph pump can produce pressure exceeding 100 psi. While this information is relevant, it only provides a partial picture of the pump's capabilities.
• Voltage: Fuel pumps have different flow rates at different voltages. Typically, fuel pumps operate at 12-13.5 volts. Higher voltages increase the pump's speed, which can impact the flow rate at a given pressure.

By considering these factors and consulting the manufacturer's guidelines, you can select the right Hilborne fuel pump size that matches your engine's requirements, fuel type, and performance needs.

Reversing the pump

• Position the pump: Place the pump so that the inlet is on your right and you are facing the cover plate end of the pump.
• Identify the dowel pin: Look for a small dowel pin in the cover. This pin indicates the rotation of the pump. If the pin is at the top 12 o'clock position, it is a front cam drive rotation. If the pin is at the bottom 6 o'clock position, it is a belt drive or rear cam drive rotation.
• Remove the cover: Take off the cover bolts and dowel pin carefully.
• Rotate the pin: Move the dowel pin to the opposite hole, rotating it 180 degrees.
• Reinstall the cover: Place the cover back on, ensuring the dowel pin is now in the opposite position.
• Caution: Sometimes, this change can result in a tight pump. If this occurs, do not operate the pump. Instead, send it back to the factory for correction.

It is important to note that reversing the pump can affect its performance and may require further adjustments to the fuel injection system. Always refer to the manufacturer's instructions or seek professional assistance if you are unsure about any part of the process.

Additionally, it is crucial to exercise extreme caution when working with fuel pumps and fuel injection systems to avoid any potential hazards.

Troubleshooting fuel pump issues

The fuel pump is responsible for delivering fuel to the engine, making it a critical component in both petrol and diesel engines. Detecting and addressing issues with your fuel pump is crucial to prevent engine damage and costly repairs. Here are some common fuel pump problems and troubleshooting tips to help you address them:

Atypical Fuel Tank Noises

If you hear unusual or loud noises coming from your fuel tank, such as whining sounds, it could indicate a malfunctioning fuel pump. These noises may be a sign that the pump is struggling to function properly and may need to be replaced.

Engine Struggles to Start or Doesn't Start

A failing fuel pump may cause your engine to struggle to start or not start at all. If your engine is not receiving enough fuel, it will have difficulty turning over. Pay attention to any popping sounds when you press the accelerator pedal, as this could indicate fuel circulation problems.

Power Loss and Decreased Performance

A faulty fuel pump can result in power loss and decreased vehicle performance, especially when driving under heavy loads or uphill. You may notice misfiring, inability to reach or maintain high speeds, or power loss when accelerating from a stop.

Poor Fuel Efficiency

If your fuel pump is not injecting fuel correctly, you may experience decreased fuel efficiency. This can be caused by a faulty fuel pump that is unable to deliver the right amount of fuel at the right time.

Visual Inspection

Perform a visual inspection to check for any leaks around the fuel pump. In some cases, you may need to use tracer gas to pinpoint the exact location of the leak.

Error Memory Check

Use a vehicle diagnostic tool, such as an OBD2 scanner, to read the error memory. Look for fault codes related to the fuel pump, such as P0251, P0230, P0148, or P0627. These codes can provide valuable information about the specific issue affecting your fuel pump.

Maintenance and Prevention

To prevent fuel pump issues, it is important to maintain your vehicle properly. This includes regular oil changes, using high-quality engine oil that meets OE specifications, and keeping your fuel level above half. Additionally, remember to replace your fuel pump as recommended, typically after 100,000 miles.

Frequently asked questions