Fuel Prime Holley: Changing The Setup From 8 To 10

Holley is a well-known manufacturer of fuel systems and other automotive parts. They offer a range of products, including fuel pumps, that cater to different vehicles and performance needs. While Holley fuel pumps are generally reliable, there may be times when issues arise, such as difficulty in priming or the need to adjust the fuel prime settings. In this guide, we will discuss the steps involved in changing the fuel prime on a Holley fuel pump, as well as some common problems and solutions related to fuel priming. We will also explore the Fuel Prime feature offered by Holley and how it can impact the starting process of your vehicle.

The Holley Fuel Prime Multiplier

In addition to the Fuel Prime Percent, the Holley Fuel Prime feature also includes a Fuel Prime Multiplier. This value multiplies the Fuel Prime Percent at CTS (Coolant Temperature Sensor) values colder than 160°F. For example, if the Fuel Prime Percent is set to 150 and the Fuel Prime Multiplier is set to 2, the amount of fuel injected will be 300% at -40°F, 200% at 60°F, and the same as the Fuel Prime Percent at or above 160°F. It is important to note that the Fuel Prime occurs 2.5 seconds after the key is turned on, so if the ignition is turned on and off quickly, the prime will not occur and the engine may take longer to start.

The Fuel Prime Multiplier can be a useful tool to help improve cold starts and reduce the need for double priming when the engine has not been started for a while. However, it is important to experiment and find the right combination of settings that work best for your specific engine and manifold setup.

Some users have reported inconsistencies with the Fuel Prime Multiplier feature, especially with single-plane manifolds. In some cases, the multiplier may not provide enough fuel for colder starts, even when set to higher values. Additionally, there have been reports of issues with the "After Start Holdoff" tuning parameter, which may not be tunable in the software. Despite these challenges, the Holley Fuel Prime Multiplier can be a valuable tool for improving the starting performance of your vehicle.

The Holley EFI Fuel Prime feature

To understand how the Fuel Prime feature works, it is important to first ensure that your Holley EFI system is properly installed. The installation process involves connecting the fuel feed and return hoses, mounting the oxygen sensor, and making the necessary electrical connections.

Once your Holley EFI system is installed, you can utilize the Fuel Prime feature by adjusting the "Fuel Prime Percentage" and the "Fuel Prime Multiplier." The "Fuel Prime Percentage" allows you to set the desired amount of fuel priming, ranging from 0 to 200%. The "Fuel Prime Multiplier," on the other hand, appears to be related to how the prime amount changes with engine temperature.

By properly configuring these settings, you can improve the starting performance of your vehicle, especially if it has been sitting idle for a prolonged period.

It is worth noting that some users have suggested additional measures to enhance starting ease, such as installing a primer pump or check valve in the fuel system. These supplementary components can further contribute to building fuel pressure and ensuring a smooth and efficient start, even after extended periods of inactivity.

Holley electric fuel pump priming

Holley electric fuel pumps are known to have priming issues. There are several ways to address this problem. One method is to pressurise the tank to force fuel into the pump. Another solution is to remove the bottom plate of the pump and unstick the vanes in the rotor, as they may be stuck in varnish or crud in the grooves. This involves disassembling the pump and cleaning or replacing the affected parts.

If you are experiencing issues with your Holley electric fuel pump not priming, there are several potential causes and solutions to consider. Firstly, check the power supply to the pump. Ensure that there is sufficient voltage reaching the pump by measuring the voltage at the pump connection. If the voltage is low, check the fuses and relay for the pump. A faulty fuse or relay can interrupt the power supply and prevent the pump from functioning properly.

Additionally, consider the age and condition of your fuel pump. If the pump is older and has not been maintained properly, it may be clogged with debris or varnish, affecting its performance. In this case, you may need to clean or replace the pump. Check the pump's filter and internal components for any buildup or blockages. If the pump is severely clogged, a rebuild or replacement may be necessary.

Another potential issue could be related to the check valve in your fuel system. A faulty or missing check valve can affect the pump's ability to maintain prime. Consider installing a check valve if you don't have one or replacing it if it is faulty. Additionally, some users have suggested using a primer pump inline with your fuel system to aid in priming and improve starting.

Finally, if your fuel pump is belt-driven, you may need to take additional steps to prime the system. One method suggested by a user is to loosen the tension on the pump belt and use a spare belt to drive the pump with a drill until fuel pressure is built up. This can be a temporary solution to prime the pump before restarting the engine.

It is important to consult a professional or a mechanic if you are unsure about any of the procedures mentioned above. They will be able to provide specific advice and guidance based on your vehicle's unique characteristics and the exact model of your Holley electric fuel pump.

Turning off the Holley Fuel Prime

Understanding the Holley Fuel Prime:

The Holley Fuel Prime feature is designed to ensure that the fuel system is primed before starting the engine. This is especially useful if your car has been sitting for a while, as it can help build fuel pressure quickly. However, it is not a mandatory step, and with the right setup, it can be turned off.

Steps to Turn Off Holley Fuel Prime:

• Locate the Fuel Prime Setting: Access the Holley Sniper EFI software and navigate to the Fuel Prime setting. This is where you will be able to enable or disable the feature.
• Uncheck the Fuel Prime Box: Simply uncheck the box that enables the Fuel Prime feature. This will disable the prime function, and the ECU (Engine Control Unit) will not activate it during the initial power-up.
• Understanding the Impact: When you disable the Fuel Prime, the ECU will still run the fuel pump, but it won't open the injectors until it detects an RPM signal. This is similar to the accelerator pump shot of fuel in a carburetor, which wets the intake manifold.
• Check Valve Considerations: Keep in mind that a check valve in the fuel system doesn't necessarily impact the initial prime shot. Its main function is to maintain fuel pressure and keep the pump and supply system pressurized, depending on your setup.
• Testing and Optimization: If you want to fine-tune your setup, you can experiment with disabling the Fuel Prime and increasing the Cranking Fuel parameters. However, for cold starts, the prime shot is crucial, and you may need to rely on it until the engine warms up.
• Cranking and RPM Detection: If you start cranking immediately after turning the key, the fuel prime shot may still occur if the ECU detects an RPM signal before initiating the prime shot. Typically, this happens within 1.5 seconds of turning the key.

Remember, turning off the Holley Fuel Prime is a matter of personal preference and depends on your vehicle's specific needs. Always refer to your Holley Sniper EFI manual for detailed information and consult with automotive professionals if you have any questions or concerns.

Holley Sniper EFI initial pump prime

To get your Holley Sniper EFI system up and running, you'll need to follow the instructions that come with the system. Here are some additional tips to help with the initial pump prime:

First, make sure you have the correct fuel pressure. The feed pressure should be around 58 PSI, and the return line pressure should be close to zero. If your feed pressure is lower than expected or if the return line pressure is above 4-5 PSI, you'll need to find and fix the restriction before proceeding.

Next, ensure that your fuel pump is properly grounded. The ground strap should go directly from the battery to the engine, and you should remove any paint, powder coating, or other material from the connection point to ensure a clean connection. In addition, the fuel pump needs to be gravity-fed, so make sure the pump inlet is at or below the bottom of the tank and as close to the tank as possible. Avoid using 90-degree fittings between the tank and the pump, as these can add significant restriction to the fuel flow.

When installing the return line to the tank, make sure it delivers the returned fuel below the fuel level. If you're using a fuel cell with two ports in the sump, don't run the return into the port parallel to the feed. Instead, install it in a way that returns the fuel below the fuel level to avoid aerating and foaming the fuel, which can damage the pump and cause drivability issues.

Finally, check that your fuel pump is properly mounted and picking up fuel. If your tachometer shows "Stall" instead of RPM when you turn the key to run, you may need to disable the rev limit verification feature on your ignition box. Also, check your cranking voltage; if it drops below 11 volts, you may need to replace your battery with one that can handle the cranking requirements of your vehicle.

Frequently asked questions