Diagnosing And Repairing High-Pressure Fuel Pumps: Is It Possible?

A high-pressure fuel pump is an indispensable part of modern fuel systems, delivering fuel to the engine and generating the pressure required for injection. However, these pumps can malfunction or fail due to various reasons, such as lack of maintenance, sensor issues, mechanical damage, or contamination. While repairing a high-pressure fuel pump is possible, it is generally recommended to replace it, especially in the case of severe defects. The repair process can be moderately complicated and may require specialised knowledge and tools. The average cost of repairing or replacing a fuel pump can range from $750 to $1900, with parts costing around $500 to $600 and labour costing between $600 and $700.

Fuel pump replacement cost

The cost of replacing a fuel pump varies depending on the make and model of your car, the ease of accessibility, and the location of the repair. The average cost to repair a fuel pump ranges from $750 to $1900, with labour costs making up a significant portion of the total cost.

For example, the cost of replacing the fuel pump in a 2005 Nissan Altima can range from $620 to $1420. The cost of the pump itself can vary from $180 to $350, while labour costs can range from $100 to $150 per hour, with a minimum of two hours for removal, installation, and dealership checks.

More expensive vehicles with complex designs can cost up to $2500 to have a fuel pump replaced. The average fuel pump replacement cost is between $834 and $874, with about 80% of the cost attributed to the parts. Good-quality fuel pump sets typically cost between $200 and $1000, while labour costs can range from $150 to $350.

It is worth noting that repairing a fuel pump is generally not recommended, as it is only a temporary solution.

Fuel pump failure symptoms

Fuel pump failure can be caused by a variety of factors, including human error, mechanical damage, and irregular maintenance. Here are some common symptoms of a failing fuel pump:

• Atypical fuel tank noises: A failing fuel pump may emit whining or loud noises from the fuel tank. Normally, the pump should make a low humming sound when the engine is started, indicating that fuel is circulating through the system.
• Engine struggles to start or doesn't start at all: A failing fuel pump may cause the engine to struggle to start or not start at all. This could be due to insufficient fuel being delivered to the engine.
• Power loss and decreased performance: A faulty fuel pump may result in power loss, especially when driving under heavy loads or uphill. The vehicle may struggle to keep up with increased fuel demands and exhibit misfiring or an inability to reach or maintain high speeds.
• Poor fuel efficiency: A failing fuel pump may lead to decreased fuel efficiency as it fails to inject the correct amount of fuel into the engine.
• Engine surging: A faulty fuel pump may cause the engine to surge, resulting in speed spikes and drops during driving.
• Lower fuel pressure: A weak fuel pump may not be able to create enough pressure to start the engine or keep it running.
• Engine stuttering and stumbling: Intermittent coughing and sputtering while driving could be an early sign of a failing fuel pump.
• Engine won't take the throttle: As the fuel pump approaches failure, it may not be able to supply enough fuel when demand is high, such as during acceleration or merging on the freeway.
• Car cuts off for no reason: A failing fuel pump may cause the engine to cut off unexpectedly, even while driving.
• Frequent trips to the gas station: If your relief valve is failing to open, more fuel than necessary may be flowing into the engine system, leading to more frequent refuelling.

It is important to note that some of these symptoms could be caused by other issues, such as bad fuel, damaged fuel lines, or a clogged fuel filter. Therefore, it is recommended to consult a qualified technician for a comprehensive inspection and diagnosis.

Fuel pump testing methods

Visual Inspection

Check for any leaks around the fuel pump. In most cases, you can detect this without additional equipment, but in some cases, you may need to use a tracer gas to check the exact location of the leak.

Checking the Error Memory

Use a vehicle diagnostic tool such as an OBD2 scanner to read the error memory. Some of the fault codes for the incorrect function of a fuel pump are:

• P0251: Fuel injection pump fuel metering control
• P0230: Malfunction of fuel pump primary circuit, such as low voltage
• P0148: Fuel supply error
• P0627: Fuel pump "A" control circuit open

Testing Fuel Pump Voltage and Amperage

This can help pinpoint electrical problems that prevent your pump from working correctly. You will need a basic digital multimeter, and optionally, a wiring diagram from a service manual or online resource. Here are the steps:

• Locate the pump's connector, which may be near the tank, access panel, or under the hood.
• Disconnect the connector carefully.
• Set the multimeter to DC Volts (usually 12-14 volts is expected for modern vehicles).
• Identify the positive and ground wires (check your wiring diagram if unsure).
• Test at the connector by touching the meter probes to the pins with the key on and the engine off. Check against your car's specifications.
• Set the multimeter to Amps (DC) and select a range that exceeds the pump's expected draw.
• Bypass the fuse (if necessary).
• Connect in series so that the multimeter becomes part of the circuit, and the pump draws current through it.
• Turn the key on and check the reading with the engine off. Compare this to your car's specifications.

Interpreting the results:

• Low voltage could indicate bad wiring, a faulty relay, a weak fuse, or a poor ground connection.
• High amperage could mean a struggling pump, possible short circuit, or a clogged fuel filter.
• No voltage or amperage could be due to a blown fuse, bad relay, or broken wire.

Performing an Electrical Test

• Check the fuel pump fuse in the fuse box. If the fuse is blown, replace it and try again.
• Check the voltage at the pump itself. Consult your vehicle's service manual to find the proper procedure for checking it.
• Perform a drop test using a voltmeter to ensure the power wire shows the full voltage and the grounding wire is properly grounded.

Performing a Fuel Pressure Test

• Remove the filter from the vehicle and drain any excess fuel. Use a short piece of rubber hose on the filter inlet.
• Blow through the filter inlet, paying attention to the resistance, which should be minimal. Inspect the screen for debris and replace the filter if necessary.
• Get a fuel pressure gauge and hook it up to the fuel pump test fitting, usually located near the fuel injectors.
• Have an assistant rev the engine while you check the gauge. Check the pressure at idle speed and at the rated speed listed in your pump specifications.
• If the pressure does not match the specifications or does not increase as you rev the engine, you may need to replace your fuel pump and filter.

Fuel pump maintenance

Weekly Visual Inspections

Routine visual inspections can identify signs of wear or damage early on, preventing potential breakdowns and costly repairs. Inspect your pumps at least once a week to check for leaks on pumps, filters, hoses, nozzles, joints, and fittings. Detecting problems early can prevent them from escalating into bigger issues.

Keep Them Clean

Although the appearance of your pumps isn't always a priority, keeping them clean can preserve their functionality and keep your team healthy. Fuel pumps are high-touch points, so you can help prevent the spread of germs by routinely cleaning them with a degreaser and gentle cleanser. Be careful not to use harsh solutions; ammonia-based cleansers can damage the screens and other vital components.

Spill Management

Inevitably there will be spills near your fuel pumps, and while these fluids can leave stains, it's important to remove them in a timely manner. Start by soaking up excess fuel with spillage absorbent granules and then use a pressure washer to remove stubborn stains.

Underground Tank Checks

Regularly inspect the overfill alarms installed in your underground tanks to ensure they are functioning correctly. These alarms promptly identify leaks, helping you mitigate potential hazards and avoid costly repairs.

Proactive Problem-Solving

Stay ahead of potential issues by scheduling your maintenance appropriately. Depending on the frequency of use, you may need to conduct weekly operational checks and monthly inspections. Addressing any issues promptly ensures the smooth operation of your fleet and reduces the risk of downtime.

Maintenance Contracts

You can also enter into a maintenance contract with a service provider to satisfy all your fuel pump maintenance requirements. They will have a large stock of spares for most pump models and a computerised call logging system to keep their service operation efficient.

Fuel pump replacement procedure

When to Replace a Fuel Pump

Be vigilant for any signs of a faulty fuel pump, which is responsible for delivering fuel to the engine. Some common symptoms of a failing fuel pump include:

• Atypical fuel tank noises
• Engine struggles to start or doesn't start at all
• Power loss and decreased performance
• Poor fuel efficiency

Preparations for Replacing a Fuel Pump

Before starting the replacement, gather all the necessary tools and components, such as a new fuel pump and fuel filter. If possible, reduce the fuel level in the tank to minimise the risk of spillage. Ensure you have a safe and accessible workspace, and take safety precautions such as disconnecting the battery.

Steps to Replace a Fuel Pump

• Relieve the fuel system pressure. This can be done by running the engine and pulling the fuel pump relay, or by pressing the Schrader valve on the pressure line momentarily.
• Locate the fuel tank and, if necessary, remove it from the vehicle. This process varies depending on the vehicle, and you may need to use a jack to support the tank. Alternatively, some models have an access port under the rear seat or in the trunk.
• Take note of the fuel line connections and wiring before removing the old pump.
• Remove all connections, turn the large lock nut to free the old pump, and pull it out.
• Reassemble the fuel system, ensuring all connections are secure.
• Test the new fuel pump to ensure it is functioning correctly.

Tips for Replacing a Fuel Pump

• Work in a well-ventilated area to minimise the risk of fire and inhalation of fumes.
• Always wear safety gear, including glasses, gloves, and appropriate clothing, to protect against fuel spills.
• Drain the fuel tank, if possible, to reduce the risk of spills and make the tank lighter and easier to handle.
• Clean around the fuel pump to prevent dirt and debris from falling into the fuel tank.
• Consider replacing related components, such as the fuel filter, fuel pump strainer, and fuel tank O-ring or gasket.

Frequently asked questions