Troubleshooting A Non-Starting Car: Checking Fuel Pressure

If your car won't start, there could be a range of issues related to fuel, compression, or spark. One common culprit is a bad fuel pump. Before spending money on a new fuel pump, you can troubleshoot the problem by checking the fuel pressure. To do this, you'll need a fuel pressure tester or gauge, which you can attach to the Schrader valve or test port on the fuel rail. With the engine off, attach the tester and turn the ignition to the on position. Check the psi reading and compare it to the recommended pressure for your vehicle, which can be found in the manufacturer's manual or a repair manual. If the pressure is low or zero, this could indicate a problem with the fuel pump, fuel filter, fuel injectors, or fuel pressure regulator. However, it's important to note that fuel pressure requirements vary by engine, so be sure to consult the appropriate specifications before drawing conclusions.

Check the Schrader valve

If your car won't start, it's important to check the fuel pressure to see if the engine is getting enough fuel. Checking the Schrader valve is a crucial part of this process. Here's a step-by-step guide on how to do it:

Locate the Schrader Valve:

First, you need to find the Schrader valve, which is usually located on the fuel rail of your engine. In some cars, it may be hidden under a fuel rail cover or another plastic engine cover. So, make sure to check your car's manual or look for it online for your specific car model.

Prepare the Schrader Valve:

Once you've located the Schrader valve, remove its cap. Before attaching the fuel pressure tester, you need to release the fuel pressure from the fuel rail. To do this, use a small flat-blade screwdriver to press down on the valve stem inside the Schrader valve, just like you would when releasing air from a bicycle tire. Wrap a large rag or towel around the valve to catch the fuel that will spray out under pressure. Don't worry, the fuel will only spray for a few seconds.

Attach the Fuel Pressure Tester:

Now, it's time to attach your fuel pressure tester to the Schrader valve. Make sure the connection is tight by using a pair of slip joint pliers. Ensure that the gauge is clear of any moving engine parts.

Start the Car and Check the Pressure:

With the fuel pressure tester attached, start your car and let it idle for about 15 seconds. Then, turn off the vehicle and check the reading on the pressure gauge. Compare this reading to the recommended fuel pressure for your specific car model. If the pressure is significantly lower than the recommended value, you may have a dirty fuel filter or a faulty fuel pressure regulator.

Release the Pressure and Reassemble:

After taking the reading, release the pressure from the fuel rail by loosening the connection slightly while still wrapped in a towel. Then, remove the fuel pressure tester, replace the cap on the Schrader valve, and reassemble any parts that you removed to access the valve.

It is important to note that fuel vapors are highly flammable, so ensure you perform these steps in a well-ventilated area and have a fire extinguisher nearby. Additionally, always refer to your car's manual or seek advice from a qualified mechanic if you're unsure about any part of the process.

Test the ignition

If your car won't start, there could be a problem with the ignition. Here are some ways to test it:

Check the Ignition Switch

A faulty ignition switch could be the reason your car won't start. The ignition switch carries power from the battery to the starter motor, which is responsible for cranking the engine. If the ignition switch is faulty, the starter motor won't receive power, and the engine won't crank when you turn the ignition switch on. You may not hear any clicking or clunking noise when you start the car. However, the lights and the horn may still work because there are separate wiring harnesses for the starter motor and other electrical components.

Test for Clicking Noise

If you hear a clicking noise when you start the car, the ignition switch is likely functioning properly. In this case, the problem may lie with the starter motor or another component.

Check for Flickering Dashboard Lights

A faulty ignition switch may cause electrical issues, such as flickering or dying dashboard lights. If you notice these symptoms, it could indicate an issue with the ignition switch.

Try Jiggling the Key

If jiggling the key in the ignition helps start the car, there might be an issue with the ignition lock or ignition switch. This is a common problem, especially in older cars.

Check the Security Light

Today's cars have an immobilizer or security system that allows starting the engine only if the correct key is used. If the security light stays on or flashes repeatedly when you turn the ignition on, it means that the car's security system does not recognize the key or there is a problem with the system itself.

Check the Steering Wheel

If the steering wheel is locked, try wiggling it left and right while gently trying to turn the key. This action may help release the steering lock, and you should be able to turn the ignition on once it's unlocked.

Check the Gear Shift

Ensure that the gear shift is in the "Park" or "Neutral" position. Modern cars have a safety feature that prevents the ignition from turning if the gear shift isn't in the correct position. Jiggle the gear shift to ensure it is fully engaged, and then try turning the key again.

Check the Battery

A dead or weak battery could cause the ignition to lock up. Restoring power to the battery or jump-starting the vehicle may resolve the issue and allow the necessary electronic communication to take place to unlock the ignition.

Try a Spare Key

If you have a spare key, try using it in the ignition. Over time, the edges of your primary car key may wear down due to frequent use, and a spare key with sharper edges may turn the ignition successfully.

Use a Silicon-Based Lock Lubricant

If your spare key doesn't work, the issue may lie with the ignition itself. Try using a silicon-based lock lubricant in the ignition to clean the wafers and remove any dirt or debris that could be preventing the key from turning.

Jiggle the Key in the Ignition

If the lubricant doesn't work, gently jiggle the key in the lock as you turn it. This method may help free up any damaged or jammed wafers in the ignition.

Tap the Key in the Ignition

As a last resort, you can try tapping the key in the ignition. Insert the key most of the way, then use a screwdriver or hammer handle to rap the key with medium force while gently trying to turn the ignition. This method uses considerable force to free up any damaged or jammed wafers.

If none of these solutions work, you may need to consult a professional mechanic or locksmith to diagnose and repair the issue.

Check the battery voltage

If your car won't start, a low or dead battery is often the culprit. To check the battery voltage, you can use a multimeter, a device that tests electrical circuits. This is a simple test that can be done in a few easy steps.

First, locate your car battery. You can consult your owner's manual for this. Check the positive and negative terminals for any dirt or corrosion. The positive terminal usually has a red cover and a "plus" sign, while the negative terminal has a black cover and a "minus" sign. If there is any corrosive buildup, scrub it off with fine-grit sandpaper. Be sure to wear gloves to protect your skin from harmful chemicals and battery acid.

Next, prepare your multimeter. Set it to voltage and ensure it's adjusted to 20 DC volts. If your voltmeter does not have incremental settings, simply set it to DC volts.

Now, touch the probes to your battery terminals. Press each probe to the correct terminal, touching negative to negative and positive to positive. Your multimeter and battery are likely colour-coded, so the negative terminal and probe will be black, while the positive terminal and probe will be red.

Finally, check the reading. A starting voltage on any battery is 12.4 volts or more. If your battery is below 12 volts, it is suspect. If the battery voltage is above 12 volts, turn the vehicle's key to the "run" position and recheck the multimeter. Compare the reading to the voltage figures below.

The temperature outside affects the voltage of the battery. At about 80 degrees, a fully charged battery will be around 12.5 to 12.6 volts. More specifically, a fully charged battery ideally measures at 12.66 volts and above, but 12.6 volts at 80 degrees, 12.588 volts at 30 degrees, and 12.516 volts at 0 degrees are all acceptable readings. A 75% charged battery will measure closer to 12.45 volts, while anything below 12 volts indicates that the battery is effectively discharged.

If you get a reading between 12.3 and 12.5 volts, try charging the battery to full and then turn on the headlights and the heater blower motor to check the voltage. The voltage should drop by a few tenths but shouldn't be drastic. If the car still won't start, do a multimeter test on the battery while someone attempts to crank the car. Observe the reading. A good battery will only drop by about 1 to 1.5 volts during the load and then quickly return to full charge. If you notice the battery drop from 12.5 down to 8 or 9 volts, this indicates that the battery may be bad.

Check the engine codes

If your car won't start, checking the engine codes can help you identify the issue. Modern vehicles are equipped with an onboard diagnostics (OBD) system that allows the car to self-diagnose and report issues by storing diagnostic trouble codes (DTCs). You can access these codes using an OBD-2 scanner, which you can usually plug into a port on the driver's side of the car. If you don't have an OBD-2 scanner, there are alternative ways to check the codes:

Using Your Odometer Reset

• Press and hold the odometer's reset button.
• While holding the reset button, press and hold the odometer's trip button.
• With both buttons held down, turn the ignition switch to “on”.
• After turning the ignition on, release the odometer buttons.
• The diagnostic trouble code should appear in your odometer display for you to record.

Using Your Odometer Reset with Multiple Ignition Cycles

• Press and hold both the odometer's reset and trip buttons.
• While holding down both buttons, turn the ignition switch to “on".
• Hold the odometer buttons while turning the ignition switch back to the “off” position.
• Without letting go of the odometer buttons, turn the ignition switch back to the “on” position.
• Release the odometer buttons to display the trouble code in the odometer window.

Using the Ignition Key and Checking the Dashboard

• Turn the key in the ignition “on” and “off” three to five times without turning on the engine, ending with the ignition in the “on” position.
• Check if all the warning lights on your dashboard illuminate.
• Observe if all lights turn off except the check engine light.
• Check if the diagnostic trouble code appeared in the odometer display.
• If not, carefully watch the engine light and record the pulses and pauses to determine the trouble code.

Using a Paperclip to Access Diagnostic Trouble Codes

• Ensure your car is turned off.
• Locate two terminals on your vehicle’s OBD port underneath the steering wheel.
• Create a closed circuit to your onboard diagnostic system by connecting the two ports with a paperclip or jumper wire.
• Turn the ignition switch to the “on” position without cranking the vehicle.
• Record the pattern of pulses and pauses on your engine light to obtain your check engine trouble code.

Once you've identified the trouble code, you can refer to a repair manual or seek assistance from a mechanic to address the specific issue.

Test the fuel pressure with a fuel pressure gauge

To test the fuel pressure with a fuel pressure gauge, start by locating the Schrader valve fitting on the fuel rail. This is usually found on the fuel rail, but it may be hidden under a fuel rail cover or other plastic engine cover. Once you've found the Schrader valve, remove the Schrader valve cap.

Next, attach the fuel pressure tester fitting to the valve. Ensure that it is properly threaded on for a leak-proof fit. Then, turn the ignition to "on," but not start. Check the psi reading on the tester and wait for a few minutes to see if there is a drop in pressure, which would indicate a leak in the system. If the pressure remains the same, the system is holding pressure well.

If the pressure drops—for example, by 20 psi in 10 minutes—there is a leak in the fuel system. Check for drips underneath the car to help locate the leak. Keep in mind that the leak could also be internal, caused by a faulty fuel injector.

Now, start the engine and let it idle. The fuel pressure should remain steady, within a few psi of the recommended pressure for your specific engine. You can find this information in your vehicle's repair manual or owner's manual. Once the engine is warmed up, slowly rev the engine and ensure that the pressure rises with the RPMs.

If your fuel pressure holds steady, rises with engine speed, and matches the recommended pressure, your car's issues are likely not fuel-related. However, if you are experiencing low or zero fuel pressure, this could indicate a problem with the fuel pump or a clogged fuel filter. On the other hand, high fuel pressure could be caused by a clogged or kinked fuel return line, a faulty fuel pump driver module, or a faulty fuel pressure regulator.

Frequently asked questions