Replacing The Fuel Pump In Your Classic Chevy 4X4

If you're looking to replace the fuel pump in your 1979 Chevy 4x4, you've got a few options. Firstly, you'll need to decide whether to remove the bed or drop the fuel tank. Both methods have their pros and cons, and the right choice depends on your preferences. It's also worth noting that older cars with carbureted engines typically have mechanical fuel pumps, while electric fuel pumps are more common in newer models. Electric fuel pumps offer better performance and meet stricter emission requirements, but they are more expensive. When replacing your fuel pump, make sure you work in a well-ventilated area, free from heat sources, sparks, and open flames.

Troubleshooting a fuel pump problem

Step 1: Check for Fuel or Vapor Lock:

If your 1979 Chevy 4x4 is experiencing issues such as running for only ten minutes and then shutting off, it could be due to a fuel or vapor lock. To confirm this, check if there is sufficient fuel in both tanks and ensure the tank vents and breather lines are clear. You can also try running the engine with the fuel cap off the tanks or using a small jerry can plumbed directly to the fuel pump inlet to determine if the issue is with the tanks or fuel lines.

Step 2: Check the Ignition and Electrical Systems:

Before assuming the issue is solely with the fuel system, it's important to check the ignition and electrical systems. Ensure that you have spark and that the ignition system is functioning properly. If the problem persists, then it's likely a fuel-related issue.

Step 3: Verify Fuel Pressure and Spark:

To narrow down the cause of the problem, you need to determine if you are losing fuel pressure or spark when the engine cuts out. One way to test this is by spraying carb cleaner or ether into the throttle body when the engine dies. If the engine starts and dies again, it's likely a fuel-related issue.

Step 4: Inspect the Fuel Line Routing:

Vapor lock can occur if the fuel line is too close to the exhaust or engine, causing the fuel to heat up and vaporize. Carefully inspect the entire fuel line to ensure it is not routed too close to any heat sources. If necessary, reroute the fuel line to maintain a safe distance from heat-generating components.

Step 5: Check the Fuel Pump Installation:

If you have recently installed a new fuel pump, ensure that it was installed correctly and that any necessary adjustments have been made. Improper installation or incorrect adjustments can lead to fuel pump issues. Refer to the installation instructions or seek advice from a qualified mechanic if you are unsure.

Step 6: Test the Ignition Components:

If the issue is not fuel-related, it could be due to a problem with the ignition system. Test the spark at the plug wires when the no-start condition occurs using a HEI spark tester. Additionally, inspect the two small wires that connect to the ignition module and the pick-up coil inside the distributor for any signs of damage or breakage.

Step 7: Seek Professional Assistance:

If you are unable to identify or resolve the fuel pump problem, it is recommended to consult a certified mechanic or a specialist familiar with Chevy trucks. They will have the knowledge and tools to diagnose and repair the issue correctly.

Removing the old fuel pump

To remove the old fuel pump from your 1979 Chevy 4x4, you will need to first relieve the fuel line pressure. Pull the fuel pump relay from the fuse box and start the vehicle. Let the engine run until it shuts down by itself. This will help relieve the pressure in the fuel line and the pump. Make sure you are working outdoors or in a well-ventilated area, away from any heat sources, sparks, or open flames.

Next, you will need to lift the truck and place it on jack stands. Use the appropriate lifting points and place the jack stands in the manufacturer's recommended locations on level ground. If you don't have access to a lift, it is recommended to use four jack stands and lift the entire truck.

Now, locate the fuel filler neck on the driver's side of the tank and above the frame. Use a stubby flat-head screwdriver to loosen the hose clamp and remove the fuel filler neck. Then, move to the passenger side of the tank and disconnect all the lines going into the top of the tank. Start with the vapor line and then disconnect the larger supply line. These lines have connectors that you can squeeze at the base to release. Be prepared for some fuel spillage when removing these lines. Wear safety goggles to protect your eyes from gasoline.

At this point, you will need to disconnect the power lines to the fuel pump. There are two quick-release electrical plugs on top of the fuel tank that need to be disconnected. Once that's done, you can proceed to remove the gas tank straps using a 15 mm socket and ratchet with a long extension. For the rear strap, you may need an assistant to hold the tank while you remove it, as it will be heavy. Alternatively, you can use a hydraulic floor jack to support the tank while you remove the straps.

With the tank straps removed, carefully lower the tank. It is advisable to have the tank as empty as possible to reduce the weight. Once the tank is on the floor, clean around the fuel pump to remove any debris, leaves, or rust. You don't want any of that falling into the tank.

Now, you are ready to remove the fuel pump. Disconnect the three lines from the fuel pump by squeezing the quick-release clips with one hand and pulling the hoses off with the other. Once the hoses are off, turn the locking ring counter-clockwise to release it. Then, lift the fuel pump module out of the tank. It will drain some fuel, so be careful and go slow.

At this point, you have successfully removed the old fuel pump from your 1979 Chevy 4x4. Remember to dispose of the old fuel pump properly and take appropriate safety measures when handling gasoline.

Installing an electric fuel pump

If you own a classic Chevy, you may want to consider replacing your mechanical fuel pump with an electric one. Electric fuel pumps offer better performance, are more efficient, and are easier to work on. They also deliver precise, high-pressure flow rates that offer maximum horsepower to the engine and meet stricter emission requirements.

Two Options for Installation

You have two options when installing an electric fuel pump:

• Leave the mechanical pump in place and put an electric one by the tank: This is a good option if you want a backup in case your electric fuel pump fails. However, this is generally unnecessary as electric fuel pumps are designed to last a long time.
• Remove the mechanical pump and replace it with an electric pump: This is a simpler solution as you can upgrade your entire fuel pump system in one go.

Step-by-Step Guide

Step 1: Uninstall the mechanical fuel pump

Remove the old mechanical fuel pump from your Chevy.

Step 2: Cover the hole

Use a block-off plate gasket and sealer to cover the hole left by the removed mechanical pump.

Step 3: Mount the electric fuel pump

Mount the electric fuel pump near the gas tank, ensuring it is not too high or in an enclosed area. A good practice is to mount it under the tank. Keep the pump away from heat sources, such as the exhaust and other heated areas.

Step 4: Connect the fuel line

Connect the electric fuel pump to the fuel line. Remember that electric fuel pumps do not pull fuel as well as they push it, so mounting it close to the gas tank is crucial for optimal performance.

Step 5: Install a filter

Install a filter next to the electric fuel pump.

Step 6: Wire the electric fuel pump

Wire the electric fuel pump to the ignition switch.

Common Mistakes to Avoid

• Mounting the pump far away from the gas tank: As mentioned earlier, electric fuel pumps do not pull fuel as well as they push it, so mounting it close to the tank is essential.
• Mounting the fuel line near heat sources: Keep the pump and fuel line away from heat sources to prevent issues with fuel and heat.
• Mounting the pump in an enclosed area: Do not mount the pump in enclosed areas such as the trunk or interior of your car. This is to keep pressure off the fuel lines and reduce the risk of fuel leaks or fires.
• Not having an automatic shut-off system: It is crucial to have an automatic shut-off system in place. In case of a malfunction, you want your engine to shut off automatically to prevent raw fuel from spraying onto hot components.
• Mounting the pump in a high area: Mounting the pump too high will make it work harder to siphon fuel, reducing its lifespan and causing it to under-deliver fuel to the engine.

Tools and Materials

Make sure you have the following tools and materials before starting the installation:

• An electric fuel pump that fits your Chevy's year, make, and model
• All the wires to connect the pump to your car, or a universal wiring kit if you want to rewire the entire vehicle
• A block-off plate gasket and sealer
• A mount for the electric fuel pump

Final Thoughts

By following these steps and avoiding common mistakes, you can successfully install an electric fuel pump in your classic Chevy. Remember to be cautious when working with fuel and always work in a well-ventilated area.

Installing a mechanical fuel pump

Step 1: Disconnect the Fuel Lines

Before removing the old mechanical fuel pump, it is crucial to disconnect the fuel lines. Ensure you disconnect both the inlet and outlet lines to avoid any leakage.

Step 2: Unbolt the Pump

The next step is to remove the bolts securing the pump to the engine. Typically, there are two bolts that need to be removed. Once the bolts are out, carefully lift the pump away from the motor, being mindful of the pump arm's position.

Step 3: Manage the Pushrod

As you remove the old pump, the pump pushrod will tend to slip down, blocking access for the new pump. There are several tricks to manage this:

• Using Grease: Apply a generous amount of grease to the pushrod and slide it back up into the block. The grease will act as a temporary adhesive, holding the pushrod in place while you install the new pump.
• Using a Tool: Insert a long screwdriver, a hacksaw blade, or a thin tool through the hole in the block to hold the pushrod up. Alternatively, use a strong magnet to stick to the pushrod and then turn the engine to move the pushrod upwards.
• Using a String or Fishing Line: Loop a string or fishing line around the pushrod and pull it tight to hold it in place while installing the new pump.
• Using a Bolt: If there is a bolt hole next to the pump mounting pad, start a longer bolt in that hole to pinch the pushrod and hold it in place temporarily. Remember to remove this bolt and replace it with the correct shorter bolt afterward.

Step 4: Install the New Pump

With the pushrod managed, carefully position the new pump against the block. Ensure the pump arm is correctly aligned with the pushrod. Secure the pump with the bolts, being careful not to overtighten them.

Step 5: Reattach Fuel Lines and Test

Once the new pump is securely in place, reattach the fuel lines. Start the engine and be ready to shut it down immediately if any fuel leaks are detected.

Step 6: Common Issues and Troubleshooting

• Fuel Pump Arm Issue: Ensure the fuel pump arm is correctly aligned and not obstructing the bolts. You may need to apply some pressure to get it in place due to the heavy spring tension.
• Pushrod Management: If the pushrod keeps falling down, try using grease or one of the tool methods mentioned above to hold it in place temporarily.
• Fuel Leakage: Check for any fuel leaks around the pump, fuel lines, or connections. Tighten any loose connections and replace any damaged seals or gaskets.

Upgrading to an electric fuel pump is also an option, offering improved performance, precision, and meeting stricter emission requirements. However, this guide focuses on the process of installing a mechanical fuel pump in your classic Chevy.

Testing the new fuel pump

Prepare the Necessary Tools and Safety Measures:

• Fuel pressure gauge: This tool helps you measure fuel pressure to determine if the pump is functioning correctly.
• Multimeter: You'll need this to check the electrical connections and voltage at the fuel pump.
• Jumper wire: Useful for bypassing relays if direct testing of the pump is required.
• Protective gear: Wear gloves and safety glasses to protect yourself from fuel and debris.
• Ventilation: Ensure you work in a well-ventilated area or outdoors to avoid inhaling harmful fumes.

Testing the Fuel Pump:

Check the Fuse and Relay:

Start by checking the fuel pump fuse and relay. A blown fuse or faulty relay could be preventing the pump from working. Replace any blown fuses and test or bypass the relay.

Test the Fuel Pressure:

• Attach the fuel pressure gauge to the fuel rail or a test port on the fuel line.
• Turn the ignition key to the "on" position without starting the engine to prime the fuel pump.
• Check if the pressure falls within the manufacturer's specified range, typically around 30-50 psi. Refer to your vehicle's manual for the exact range.
• If the pressure is low or non-existent, it suggests a potential pump issue.
• Listen closely for a humming or buzzing sound near the fuel tank with the ignition on. This indicates that the fuel pump is operational. Absence of this sound could mean the pump isn't getting power or is malfunctioning.

Test the Electrical Connections:

• Use the multimeter to check the voltage at the fuel pump's electrical connector.
• With the ignition on, the voltage should read around 12 volts.
• If the voltage is low or absent, there may be an issue with the wiring, fuse, or relay.

Inspect for Fuel Leaks:

• Visually inspect the fuel lines near the pump for any signs of leaks.
• Fuel leaks can lead to a loss of pressure and pose a serious fire hazard, so replace any damaged components immediately.

Use an OBD2 Scanner (Optional):

• Using a scanner like the Foxwell NT809TS can provide real-time diagnostic data and pinpoint fuel pump or related system problems.
• Common trouble codes associated with a failing fuel pump include P0087, P0230, P0171, and P0174.

Key Indicators of a Healthy Fuel Pump:

• Stable Pressure: A functional pump maintains steady pressure within the recommended range. Dropping pressure could indicate a weak or failing pump.
• Consistent Voltage: Ensure the pump is receiving the correct voltage; inconsistent voltage could indicate an electrical issue.
• Steady Fuel Flow: The pump should deliver a consistent flow of fuel. Irregularities may suggest the pump is struggling and needs replacement.

Frequently asked questions