Getting Your Car Running After Fuel Injector Replacement

Changing fuel injectors can be a tricky process, and it's not uncommon for car owners to run into issues when trying to start their vehicle after making this repair. There are several potential reasons why a car may not start after changing fuel injectors, including problems with fuel and spark delivery, incorrect wiring, or air in the fuel line. In some cases, the engine may need to be bled to remove air from the fuel line. It's also possible that the new injectors are not functioning properly, or that there is an issue with the ignition system. Troubleshooting these issues typically involves checking for fuel and spark delivery, verifying wiring connections, and, in some cases, seeking the advice of a professional mechanic.

Check for spark and fuel

Checking for spark and fuel is essential when starting a car after changing fuel injectors. Here are some detailed steps to ensure your car starts smoothly and safely:

Check for Spark

• Inspect the spark plugs: Look for any signs of wear, fouling, or damage. If the spark plug is damaged, replace it with a new one. This is usually an inexpensive fix.
• Examine the ignition coils: Check for any cracks or other damage. Ensure that the ignition coils are firmly connected to the spark plugs and wiring.
• Inspect the spark plug wires: Look for any cracks or deterioration. If the wires are worn out, replace them with high-quality cables.
• Test for spark: Pull one spark plug wire and hold it close to a ground while wearing a rubber glove. Alternatively, use a screwdriver of the appropriate size and insert it into the wire, then hold the handle near a ground. You can also pull the main wire from the cap and hold it slightly away from the cap, then do the same with a regular plug wire. This will help you check for spark from the coil and spark to the wire.

Check for Fuel

• Check for fuel leaks: Ensure there are no leaks around the fuel injector and pump. Leaks can lead to a fuel-drenched spark plug, causing starting issues and misfires.
• Listen for the fuel injectors: Use a long screwdriver or a mechanic's stethoscope to listen to the fuel injectors. Hold it against the injector and then to your ear; you should hear a ticking sound as the engine is cranked.
• Check the fuel pump: Turn the ignition key to the "On" position, but not to the "Start" position. This will activate the fuel pump and ensure the engine receives enough fuel pressure and oil. Listen for the sound of the fuel pump running; it should stop after a few seconds, indicating that the system is pressurized. Repeat this process if needed to ensure proper pressurization.
• Warm up the engine: When starting the engine for the first time after changing fuel injectors, it may require a few extra cranks. This helps build fuel pressure and purge air from the system. Listen for the cranking noise and let the engine run for a few minutes to warm up and stabilize.

By carefully checking for spark and fuel, you can ensure that your car starts smoothly and safely after changing the fuel injectors.

Check the battery

When troubleshooting a car that won't start after changing the fuel injectors, one of the first things to check is the battery. Ensure that the battery is fully charged before attempting to start the engine. If the battery is not fully charged, connect it to a charger and allow it to charge before trying to start the car again.

If the battery is fully charged and the car still won't start, the next step is to check for flooding in the cylinders. Remove all the spark plugs and crank the engine. If the engine cranks or spins, reinstall the spark plugs and try to start the engine again.

If the engine still doesn't spin, there may be another issue preventing it from starting. In this case, further diagnostics are required to identify the root cause of the problem. It is recommended to seek assistance from a professional mechanic or a knowledgeable individual who can help troubleshoot the issue.

It is important to note that replacing fuel injectors is not a necessary maintenance item and should only be done if there is a specific issue with the injectors. Regular maintenance items such as replacing spark plugs and coils are typically sufficient to maintain optimal engine performance.

Additionally, if there is a significant drop in fuel economy or engine performance, it is advisable to diagnose the issue thoroughly before replacing parts. In some cases, issues with fuel economy may be related to factors other than the fuel injectors, such as clogged air filters or ignition system problems.

Remove spark plugs and crank the engine

Removing the spark plugs and cranking the engine is a common method to test for spark issues. Here is a step-by-step guide on how to do this safely:

Step 1: Disconnect the Spark Plug Wires

Locate the spark plugs, usually positioned on top or along the side of the engine. Disconnect the spark plug wires, ensuring you have a clear workspace.

Step 2: Remove the Spark Plugs

Using a spark plug socket and ratchet, carefully remove the spark plugs from the engine, one by one. Place them in a safe location, keeping track of which cylinder they came from.

Step 3: Ground the Spark Plug

Take one of the removed spark plugs and securely ground it to a metal part of the engine. Ensure there is no fuel or flammable material nearby.

Step 4: Turn the Ignition

With the grounded spark plug in place, turn the ignition on and crank the engine. Do not let the engine run for an extended period.

Step 5: Check for Spark

Observe the grounded spark plug. If it is functioning correctly, you should see a spark. Repeat this process for each spark plug, grounding it to the same location and cranking the engine to test for a spark.

Step 6: Reinstall the Spark Plugs

Once you have tested all the spark plugs, carefully screw them back into their respective cylinders, tightening them with the spark plug socket and ratchet. Ensure they are secure and properly connected.

Step 7: Reconnect the Spark Plug Wires

Reconnect the spark plug wires to their corresponding spark plugs. Ensure all connections are secure.

Safety Precautions:

• Always exercise caution when working with fuel and electrical systems.
• Do not smoke or have any open flames near the engine.
• Avoid wearing loose clothing or jewellery that could get caught in moving engine parts.
• If you are uncomfortable or unfamiliar with any of these steps, consult a professional mechanic.

By following these steps, you can safely test for spark issues by removing the spark plugs and cranking the engine. Remember to work carefully and methodically to avoid any potential hazards.

Check for cylinder flooding

Cylinder flooding can occur when an engine is switched off when it's still cold. This can happen when a car is moved out of a garage and then switched off to let someone else out, for example. It is most common in autumn and winter.

Small, four-cylinder engines are most susceptible to flooding, but it can happen to any petrol engine in the right conditions.

• Listen out for a loud, concerning noise when starting the engine. This is caused by lowered compression, which in turn causes the engine to turn over faster without firing, leading to a distinctive 'whirring' sound.
• Check for a strong smell of petrol, especially around the exhaust. If you have a flooded engine, the fuel is being supplied to the engine at a rate higher than it can be burned.
• The car doesn't start, or starts briefly and then cuts out again. This can happen when the engine has been supplied with more fuel than it can burn in a short period of time.
• Remove the spark plugs and check if they are wet with fuel. If they are, you might have a flooded engine.

If you have a flooded engine, you can try the following:

• Crank the engine with the accelerator pedal pushed to the floor.
• Continue cranking the engine for up to 10 seconds until you hear the engine trying to start.
• Once the engine has started, allow it to rev up for a second or two, then hold it at a higher-than-normal idle speed for a few more seconds.
• If the engine doesn't start within 10 seconds, switch off and call for assistance.

Check the wiring

After changing your fuel injectors, you will need to check the wiring to ensure that your car starts properly. Here is a step-by-step guide to help you through the process:

Step 1: Check the Wiring Harness

If your car has been in a fire or any other type of accident, it is important to inspect the wiring harness for any signs of damage. Make sure that all the wires are intact and securely connected. Look for any burnt, melted, or frayed wires, as these will need to be repaired or replaced.

Step 2: Test for Power

You can use a small test light or a multimeter to check if the injector wires are receiving power. Connect the test light to each injector wire, one at a time, and observe if the light illuminates. This will indicate that power is reaching the injectors. If the test light does not come on, there may be an issue with the wiring or the power supply.

Step 3: Listen for the Injector Tick

Use a long screwdriver or wooden handle to listen to the injectors. Place one end of the screwdriver on the injector and hold the other end to your ear. As you crank the engine, you should hear a ticking sound coming from the injectors. This indicates that they are receiving a signal and are functioning properly.

Step 4: Check for Correct Injector Installation

Ensure that the fuel injectors are installed correctly and securely fastened. Check if the injectors have caps or covers on them. Sometimes, new injectors come with protective covers to keep debris out. Make sure to remove these covers before starting the engine.

Step 5: Verify Injector Spray Pattern

To ensure proper fuel delivery, it is important to check the spray pattern of the injectors. Carefully remove the fuel injectors and spray them onto a clean towel for a few seconds. Observe the spray pattern to ensure that the injectors are dispensing fuel properly.

Step 6: Inspect for Damaged or Disconnected Wires

If your car still refuses to start, carefully inspect all the wires connected to the injectors. Make sure that none of the wires have been damaged, disconnected, or pinched during the installation process. Ensure that all the wires are securely connected and routed correctly.

By following these steps, you can effectively check the wiring after changing your fuel injectors. This will help you identify and resolve any issues that may be preventing your car from starting.

Frequently asked questions