Checking Fuel Pressure: 99 Es300 Guide

To check the fuel pressure on a 1999 Lexus ES300, you will need a high-pressure fuel pressure gauge designed for fuel injection systems. You will also need a metric banjo bolt adapter to connect the gauge to the fuel system. The testing procedure involves removing the relay box cover and circuit-opening relay, inspecting the relay for continuity using an ohmmeter, and reinstalling the relay and relay box cover. This process allows you to check for any electrical problems that may be causing low fuel pressure or other issues. It is important to follow the correct safety procedures and refer to a repair manual or seek professional assistance if you are unsure about any steps.

Check for power at the relay

To check for power at the relay of your 1999 Lexus ES300, follow these steps:

Firstly, you need to know where each circuit flows in and out of the relay. All relays have standard numbers identifying each of the four connection pins, and those numbers will be printed or embossed into the relay body next to the pins. Here’s what they signify:

• Pins 85 and 86 are on the control side of the relay. Power from the switch flows into the relay at pin 85 and out to a chassis ground from pin 86, making a complete circuit that activates the relay’s electromagnet. The magnet then closes a second independent electrical circuit, allowing high amperage to flow through it directly to a component.
• Pin 87 is where high-amperage current from the battery enters the relay.
• Pin 30 is where that current flow from the battery goes out to the component when the electromagnet is energised and the circuit closed.

Now that you know which pins are which, you can begin checking the relay. The only tool required to check a relay is a multimeter. With the relay removed from the fuse box, set the multimeter to measure DC voltage and activate the switch in the cab.

Check to see if there are 12 volts at the 85 position in the fuse box where the relay plugs in (or wherever the relay is located). If there isn’t, check to see if the appropriate fuse has blown. If the fuse is intact, ensure the switch is allowing current to flow to the relay.

Once you can confirm there is voltage at the 85 position, set the multimeter to the continuity mode and check to see if the 86 slot has a good ground connection.

If voltage is able to flow through that side of the relay, move on to the 87 connection point and determine if battery voltage is present there. If it isn’t, that also suggests a blown fuse or circuit breaker.

Checking the connection points in the fuse box with a multimeter will confirm if battery voltage is available at the relay terminals.

You can do an easy double-check of the relay, just to be sure. Simply take a cotter pin or piece of wire and connect it between the relay’s 87 and 30 connection points in the fuse box. The component should begin working. Doing this is also an efficient way to make an emergency repair that will allow you to get the machine back to the yard until the relay can be replaced. Remember, a relay is not a fuse; there will still be a fuse to protect the circuit.

Check fuses

To check the fuses in your 1999 Lexus ES300, follow these steps:

Getting Started:

Before you begin, make sure you have a basic understanding of your car's fuse box and fuse types. This will help you identify any blown fuses more easily. You can refer to your Lexus ES300's owner's manual or a repair guide for more detailed information.

Locate the Interior Fuse Box:

The interior fuse box of your Lexus ES300 is usually located on the driver's side of the vehicle, near the steering wheel or under the dashboard. Open the driver's side door and look for a panel with a fuse box diagram or a list of components and their corresponding fuses.

Remove the Cover:

Once you've located the interior fuse box, carefully remove the cover to access the fuses. The cover should be easy to remove by hand or with a simple tool like a screwdriver.

Check for Blown Fuses:

With the cover removed, you can now visually inspect the fuses. Look for any fuses that appear burnt, melted, or broken. A blown fuse will typically have a broken wire or a darkened glass tube. You can also use a fuse tester or a multimeter to check for continuity.

Identify the Fuse:

Refer to the fuse box diagram or the list of components to identify which fuse is associated with the problem you're experiencing. The diagram will indicate which fuses are tied to specific components or systems in your vehicle.

Remove and Replace the Blown Fuse:

Once you've identified the blown fuse, carefully remove it from the fuse box using fuse pullers or a small pair of pliers. Take note of the fuse's amperage or colour, as you'll need to replace it with an identical fuse. Insert a new fuse of the same amperage and ensure it is securely seated in the fuse box.

Reinstall the Cover and Test:

After replacing the blown fuse, securely reinstall the cover on the fuse box. Start your vehicle and test the component or system that was previously experiencing issues. If the problem persists, there may be another cause, such as a short circuit or a faulty component. In this case, it is recommended to consult a professional mechanic for further diagnosis and repair.

Remember to exercise caution when working with your vehicle's electrical system, and always refer to the appropriate manuals or guides for your specific vehicle model.

Use a high-pressure fuel-injection gauge

To check the fuel pressure on a 1999 Lexus ES300, you can use a high-pressure fuel-injection gauge. Here's a step-by-step guide on how to do it:

Prepare the Vehicle:

• Park your Lexus ES300 on a flat surface and ensure the engine is off.
• Locate the Schrader valve fitting on the fuel rail. It is usually found on the engine fuel rail but may be hidden under a fuel rail cover or plastic engine cover.
• Remove the Schrader valve cap.

Connect the Fuel Pressure Tester:

• Ensure you have the correct fuel pressure tester fitting for your vehicle. Most fuel pressure tester kits come with multiple fittings to accommodate different vehicles.
• Attach the appropriate fitting to the Schrader valve. Make sure it is threaded on properly to ensure a leak-proof fit.

Check the Fuel Pressure:

• With the ignition turned to the "on" position (not start), check the psi reading on the fuel pressure gauge.
• Wait and observe the gauge for a few minutes. If the pressure drops, it indicates a leak in the system.
• Start the engine and let it idle. The fuel pressure should remain steady, within a few psi of the recommended pressure for your vehicle.
• Once the engine is warmed up, slowly rev the engine. The fuel pressure should rise with the increase in RPMs.

Interpret the Results:

• Zero fuel pressure: This could mean that the fuel pump is dead or not receiving power. Check the fuel pump fuse and verify power to the pump with a multimeter. If the pump is not receiving power, check the wiring and connections.
• Low fuel pressure: A clogged fuel filter or a failing fuel pump could be the cause. Service or replace the fuel filter if it is a serviceable type. Also, check for improper tank venting or a loose gas cap, as these can affect fuel pressure.
• High fuel pressure: Suspect a clogged or kinked fuel return line, a faulty fuel pump driver module, or a faulty powertrain control module. These issues may also trigger a "check engine" light and store a trouble code. Another possible cause is a faulty fuel pressure regulator.

Finalize the Process:

• After completing the tests, remove the fuel pressure gauge and reinstall the dust cap on the Schrader valve or remove the fuel line adapter if one was used.
• Clean up any excess fuel that may have spilled during the process.

By following these steps and interpreting the fuel pressure readings, you can identify and address any issues with your Lexus ES300's fuel system.

Check the battery

To check the battery of your 1999 Lexus ES300, you will need to test the voltage of the battery using a digital multimeter.

First, make sure the engine is off. Then, set your multimeter to 20 DC volts and connect the red probe to the positive terminal of the battery and the black probe to the negative terminal. A good battery should have a voltage of 12V or slightly more. If the voltage is less than 12V, you likely have a parasitic drain.

Next, start the engine and let it idle. With the engine idling, the battery terminals should now read about 14V, which indicates that the alternator is charging the battery.

Additionally, you can test the battery daily for voltage to ensure it is holding its charge. If the battery shows a drop in voltage after sitting for several hours, this could indicate a parasitic drain.

It is also recommended to purchase a battery charger so you can test the starter yourself and charge your battery when needed.

If you are experiencing issues with your battery, it is important to get it checked by a professional. Some common issues with the Lexus ES300 include a faulty alternator, a stuck button that stores the driver's seat position creating a parasitic draw, and a marginal starter.

You can also refer to the Lexus ES300 forums and online resources for troubleshooting tips and advice from other ES300 owners who have experienced similar battery issues.

Check the ignition fuse

To check the ignition fuse of your 1999 Lexus ES300, you'll first need to locate the fuse box. In Lexus ES300 models, the fuse box is located in the trunk, along with the battery terminals.

Once you've found the fuse box, follow these steps:

• Open the fuse box: Depending on the specific model of your ES300, you may need to remove a cover to access the fuses.
• Locate the ignition fuse: The ignition fuse should be located within the fuse box. Check the fuse diagram or the fuse itself to identify the correct fuse. It may be labeled as "IGN" or "IG".
• Inspect the fuse: Remove the ignition fuse from its slot and visually inspect it. Look for any signs of damage, melting, or charring. A blown fuse will typically have a broken wire inside or appear blackened or burnt.
• Test the fuse: You can use a multimeter to test the fuse for continuity. Set the multimeter to the appropriate setting (usually the lowest ohms setting) and touch the probe tips to the ends of the fuse. If the multimeter displays a value, the fuse is good. If it doesn't display anything, the fuse is blown and needs to be replaced.
• Replace the fuse if necessary: If the fuse is blown, replace it with a new one of the same type and rating. Make sure to address any underlying issues that may have caused the fuse to blow in the first place.

It's important to note that working with automotive electrical systems can be dangerous. Always exercise caution and refer to a professional mechanic or a detailed guide if you're unsure about any steps. Additionally, always refer to your vehicle's specific instructions when working with its electrical system.

Frequently asked questions