Fuel Pressure Test Guide For '99 Dodge Durango Owners

If you're experiencing issues with your 99 Dodge Durango, it may be necessary to perform a fuel pressure test to diagnose the problem. This test will help determine if the issue is related to fuel delivery or another component of the vehicle. Before beginning the test, it's important to consult the service manual for specific instructions and safety precautions. The basic procedure involves connecting a fuel pressure gauge to the test port on the fuel rail and observing the pressure readings while the engine is running. By interpreting these readings, you can identify potential issues such as a kinked fuel supply line or a defective fuel pump or pressure regulator. Additionally, there are other tests, such as the starting fluid test, that can help determine if the issue is related to a lack of fuel or another factor.

Check the fuel pump pressure

To check the fuel pump pressure on a 1999 Dodge Durango, you will need to perform a fuel pressure test. Here is a step-by-step guide:

Step 1: Prepare the Vehicle

• Park the vehicle in a safe and well-ventilated area.
• Allow the vehicle to cool down completely before starting the test. It is important to ensure that the engine is off and the fuel system is not under pressure.

Step 2: Access the Fuel Rail Test Port

• Locate the fuel rail test port. It is usually found on the fuel rail, which is part of the engine's fuel system.
• Remove the protective cap from the test port to expose the needle valve underneath.

Step 3: Connect the Fuel Pressure Gauge

• Connect a suitable fuel pressure gauge to the test port. Ensure that the gauge can measure pressures up to 60 psi (pounds per square inch).
• If you do not have access to a fuel pressure gauge, you can skip this test and proceed to the alternative "Starting Fluid Test" described below.

Step 4: Start the Engine and Observe Pressure

• Start the engine and allow it to warm up.
• Observe the pressure reading on the gauge. The fuel pressure should be within the specified range, typically around 49.2 psi +- 5 psi at idle.

Step 5: Interpret the Results

• If the engine runs but the pressure is below 44.2 psi, check for a kinked fuel supply line between the fuel rail and the fuel pump module.
• If the fuel supply line is not kinked, and the pressure is still low, you may need to replace the fuel pump module assembly.
• If the operating pressure is above 54.2 psi, it indicates that the electric fuel pump is functioning correctly, but the fuel pressure regulator may be defective and needs replacement.

Alternative Test: Using Starting Fluid (for No-Start Conditions)

• Remove the intake air duct from the throttle body. You don't need to completely detach it, as you will reconnect it later.
• Manually open the throttle and spray starting fluid down the bore.
• Quickly reconnect the air duct to the throttle body as a safety precaution.
• Have an assistant crank the engine.
• If the engine starts momentarily and then dies after a few seconds, it confirms a lack of fuel or a faulty fuel pump.
• If the engine does not start at all, the issue is likely not related to a lack of fuel.

It is important to consult a qualified mechanic or refer to a detailed service manual for specific instructions pertaining to your vehicle.

Check Valve Operation

To check the valve operation of a 1999 Dodge Durango, you'll need to perform a fuel pressure test. This will involve checking the fuel pump pressure, which is under constant pressure even when the engine is off.

Firstly, you must release the fuel system pressure. Then, remove the protective cap at the fuel rail test port and connect a fuel pressure gauge to the test port pressure fitting on the fuel rail.

Next, start and warm up the engine, noting the pressure gauge reading. For a 1998-2003 Dodge Durango, the fuel pressure should be 339 kPa +- 34 kPa (49.2 psi +- 5 psi) at idle. If the engine runs but the pressure is below 44.2 psi, check for a kinked fuel supply line between the fuel rail and the fuel pump module. If the specifications for the fuel pump capacity, amperage, or leak-down tests are not met, replace the fuel pump module assembly.

If the operating pressure is above 54.2 psi, the electric fuel pump is functioning correctly, but the fuel pressure regulator is defective and will need to be replaced.

It is important to note that before performing any fuel system tests or maintenance, you should always refer to the vehicle's service manual for specific instructions and safety precautions.

Fuel Pump Capacity Test

To perform a fuel pump capacity test on a 1999 Dodge Durango, you will need to follow a set of specific steps to ensure an accurate reading. Here is a detailed guide on how to conduct the test:

• Purchase or acquire a fuel pressure test gauge. This tool is essential for accurately measuring the fuel pressure in your Dodge Durango.
• Remove the protective cap at the fuel rail test port. The fuel rail is part of the fuel delivery system and is located on the engine.
• Connect the fuel pressure test gauge to the test port pressure fitting on the fuel rail. Ensure a secure connection.
• Start the engine and allow it to warm up. A warm engine will provide a more accurate reading.
• Note the pressure gauge reading. For a 1998-2003 Dodge Durango, the fuel pressure should ideally be 339 kPa +- 34 kPa (49.2 psi +- 5 psi) at idle.
• If the engine runs but the pressure is below 44.2 psi, check for a kinked fuel supply line between the fuel rail and the fuel pump module. A kinked fuel line can restrict fuel flow and affect the pump's capacity.
• If the fuel supply line is not kinked but the pressure is still low, consider conducting further tests, such as the Fuel Pump Amperage Test or the Fuel Pressure Leak Down Test, as recommended in the service manual.
• If the operating pressure is above 54.2 psi, it indicates that the electric fuel pump is functioning correctly, but the fuel pressure regulator may be defective and requires replacement.
• Finally, reinstall the protective cap on the fuel rail test port.

It is important to refer to the service manual or seek professional assistance if you are unsure about any steps or if you encounter issues during the testing process.

Fuel Pressure Leak Down Test

A fuel pressure leak-down test is used to diagnose fuel system issues in a car. Here is a step-by-step guide on how to perform this test on a 1998-2003 Dodge Durango:

Step 1: Prepare the Vehicle

Ensure the vehicle is cooled down, and the fuel pressure has dropped to 0 psi. This is a normal condition when the vehicle is turned off and cooled down, as fuel contracts when cold.

Step 2: Connect the Fuel Pressure Gauge

Remove the protective cap at the fuel rail test port. Connect a 0-414 kPa (0-60 psi) fuel pressure gauge to the test port pressure fitting on the fuel rail. You may also use a DRB III Scan Tool along with the PEP module, a 500 psi pressure transducer, and a transducer-to-test port adapter instead of the fuel pressure gauge.

Step 3: Start the Engine and Observe Pressure

Start the engine and warm it up. Note the pressure gauge reading. For the Dodge Durango, the fuel pressure should be 339 kPa +- 34 kPa (49.2 psi +- 5 psi) at idle.

Step 4: Check for Low Pressure

If the engine runs but the pressure is below 44.2 psi, check for a kinked fuel supply line between the fuel rail and the fuel pump module. If the line is not kinked, and the pressure is still low, you may need to replace the fuel pump module assembly.

Step 5: Shut Off the Engine and Observe Pressure Drop

Turn off the engine and observe how the pressure changes. A basic leak-down test involves turning the key off and seeing how long the pressure holds. For most systems, the pressure should hold for about five minutes. For the Durango, the pressure should not fall below 30 psi for five minutes.

Step 6: Diagnose Leaks

If the pressure falls below the specified minimum, there may be a leak in the system. To diagnose the leak, you will need to perform additional tests. Start the engine and bring it to normal operating temperature, then shut it off.

Step 7: Test for Fuel Injector or Fuel Rail Leakage

Clamp off the rubber hose portion of the adaptor tool between the fuel rail and the test port. If the pressure now holds at or above the minimum value, there is a leak in the fuel injector or the fuel rail.

Step 8: Test for Fuel Pump Check Valve, Filter/Regulator Check Valve, or Fuel Tube/Line Leakage

Clamp off the rubber hose portion of the adaptor tool between the vehicle fuel line and the test port. If the pressure now holds, there may be a leak in the fuel tube/line. If no leaks are found, there may be a defective check valve in either the electric fuel pump or the filter/regulator. A quick loss of pressure usually indicates a defective check valve in the filter/regulator, while a slow loss of pressure points to a defective check valve in the electric fuel pump.

Step 9: Further Testing for Fuel Injector Leakage

If the source of the leak is suspected to be a fuel injector, further testing can be performed. Remove the fuel rail with the injectors still attached. Reconnect the fuel rail supply and return lines. Place catch rags under each injector tip. Start the fuel pump and observe which injector(s) is leaking. Replace or repair the leaking injector(s) as necessary.

Fuel Pump Amperage Test

To perform a fuel pump amperage test on your 1999 Dodge Durango, you'll need to follow these steps:

Firstly, it is important to understand why testing voltage and amperage is crucial. Voltage verification ensures that the pump receives the correct amount of power, while amperage testing reveals whether the pump is overworked, shorted, or has internal issues.

Now, here is a step-by-step guide to testing fuel pump amperage:

• Set your multimeter to Amps (DC): Choose a range that exceeds the pump's expected draw.
• Bypass the fuse: You may need a special fused jumper wire for this step.
• Connect in series: This step involves connecting the multimeter as part of the circuit, allowing the pump to draw current through it.
• Key on, engine off: Note the reading and compare it to your vehicle's specifications.

Interpreting the results:

• Low Voltage: Indicates issues with bad wiring, a faulty relay, a weak fuse, or a poor ground connection.
• High Amperage: Suggests a struggling pump, a possible short circuit, or a clogged fuel filter.
• No Voltage/No Amperage: Points towards a blown fuse, bad relay, or broken wire.

Additionally, here are some safety precautions and considerations:

• Work in a well-ventilated area: Gasoline fumes are flammable, so adequate ventilation is crucial.
• Follow vehicle-specific procedures: Always refer to safe testing methods designed for your specific make and model.
• Voltage Drop Test: This test can help reveal wiring harness issues under load.
• Oscilloscope: For advanced analysis and visualisation of pump voltage patterns, consider using an oscilloscope, often intended for professional use.

By conducting this fuel pump amperage test, you can accurately diagnose issues with your 1999 Dodge Durango's fuel system and make informed decisions about necessary repairs.

Frequently asked questions