Dirty fuel injectors may not be considered a significant concern when it comes to car maintenance, but they can make your car perform sub-optimally on so many levels. For starters, they may affect your car’s ability to start up. They also inject dirty fuel into the combustion chamber of your engine, causing it to produce a ton of smoke and mess up components of the engine in the long run.
So what should you look out for when trying to determine if your vehicle has clogged fuel injectors?
Clogged fuel injector symptoms
Clogged fuel injectors exhibit similar symptoms to a bad coil, a broken spark plug wire, or a bad spark plug. In most cases, the clog is caused by debris or gunk inside the injector or filter basket built up over time. And the clog cannot be reversed by constant intake of fuel. The only solution is to clean the clogged fuel injectors.
In some cases, the fuel injectors may be dirty but not necessarily clogged. While this may not ground the vehicle, it may hamper vehicle performance and affect driveability. Regular cleaning will prevent your dirty fuel injectors from being blocked.
On the other hand, if the fuel injectors are leaking, the only option is to replace them as cleaning will not fix them. While this option is expensive, it is better to be safe than sorry. Granted, you may try to patch them up and continue using them, but replacing them is the only long-term solution.
Symptoms of clogged or dirty fuel injectors include;
- Starting issues
- Poor idle
- Failed emissions
- Poor Performance
- The engine does not reach full RPM
- Increased fuel consumption
- Rough engine performance
- Surging and bucking under various throttle loads
- Smoke from the tailpipe
- Engine Knock or Detonation can lead to catastrophic engine failure
- Pollution
Symptoms of leaking fuel injectors include;
- Increased Fuel Consumption
- Poor Idle
- Fuel odors inside and around the car
- Hard Starting
- Poor Emissions
- Oil thinning, which can lead to catastrophic engine failure
- Hydro lock, which can lead to catastrophic engine failure
Note; External injector leaks are a fire hazard and cannot be fixed. You have to replace the injector as soon as possible
Other symptoms of a bad fuel injector include;
The coil is bad (resistance is out of spec or non-existent)
- Broken Return Spring
- Broken Pintle, ball, or disc
- Bad Pintle or Ball seat
- Pintle or Ball seized to the body (Rust etc.)
- Leak in the actual injector body
- The injector cannot be recovered.
How to diagnose a clogged fuel injector
Below are a series of steps you can use to test fuel injectors to determine if your vehicle has clogged fuel diagnostics;
- Start the engine when cold and let it run at idle for 5 – 10 seconds.
- Check the exhaust manifolds with your bare hands and find the one that’s not warm. Do not do this if the engine is hot.
- Use a heat marker to check if there is heat being produced from the exhaust outlet cylinders.
- If the engine is hot, there will be droplets of water on the exhaust manifold.
- Remove the connector from the injector on the cylinder while it is still cold.
- Then inspect the terminals of the injector connector to make sure it is not corroded.
- Using an ohmmeter, check if there is power being passed to the injector connector. You can also use a Noid light.
- Confirm with an ohmmeter that the injector has the proper resistance.
- Then reconnect the injector connector.
- Remove the spark plug wire, disconnect the coil pack, or remove the coil pack that goes to that cylinder.
- Start the engine. It should sound the same.
- Remove the spark plug.
- If the spark plug is dry, then the injector does not deliver fuel to that cylinder.
- If the spark plug is wet and smells like gasoline, then the injector on that cylinder is not your problem.
- Once you have confirmed there is voltage using a multimeter, then the underlying issue causing the exhaust to be cold is clogged fuel injectors. You can also test the terminals for resistance. No resistance means that the injector is not working.
- Reinsert the injector, and if the symptoms experienced before remain, the fuel injector is clogged.
Check this too: How to Remove Rusted Bolts
How to clean fuel injectors without removal
The easiest way to clean fuel injectors is by using an injector cleaner. The cleaner will loosen any gunk or debris clogging the filters. However, in some cases, this may make the problem much worse as the loose debris may end up blocking the injector pathways making it even harder to get the debris out.
This method is best used on fuel injectors that are just dirty and not severely clogged. It is a beginner-friendly method for cleaning a fuel injector while it’s still in the car. Follow these steps to clean your fuel injectors regularly;
- Pour your fuel injector into the tank.
- Then add a full tank of gas.
- For a thorough cleanse, use a second bottle or wait until the next time you use gas.
- You can repeat this process after every 7,000 miles or at every oil change.
How to thoroughly clean fuel injectors
If the method does not unclog your fuel injectors, you may need to perform an extensive fuel injector cleaning service. This may require some dismantling and reassembly.
Items needed:
- Fuel injector cleaner kit
- Flexible rubber hose
- Steel hose clamps
- A battery
- A drip pan
- Crocodile clipped electrical leads
- New fuel injector ‘o’ rings
- Nitrile gloves protect your hands from chemical solvents and fuel.
- Long-sleeve shirt to protects your arms.
- A mask or respirator to filter the fumes and odors.
- Eye protection.
- Wrench set (socket and regular)
- Air compressor (for cleaning kit)
Steps to clean the fuel injectors;
- Follow the manufacturer’s instructions on the fuel injector cleaning kit.
- Remove the cap from the fuel injector canister.
- Then fill the canister with recommended cleaning solution.
- Hang the canister under the hood in a convenient location above the engine.
- Locate the fuel rail test port (refer to user manual).
- Attach the canister hose to the fuel rail test port using the proper adapter.
- Locate the fuel pump relay in the fuse box and disconnect it.
- Then attach air supply to the canister’s airport.
- Adjust regulated system pressure, displayed on the meter, as directed (usually a few pounds lower than average fuel-rail operating pressure).
- Start car and wait until all of the solutions have flowed through the fuel rail and the canister is empty (5-10 minutes).
- Release the line pressure and disconnect the air supply and disconnect the hose from the fuel rail.
- Start the car to see if the cleaning session was a success.
Note: use fuel additives when storing your car for prolonged periods to reduce fuel injectors’ clogging probability. Always use the correct fuel for your cat to ensure the injectors do not get clogged.
Lastly, if you cannot do the job properly, it is best to hire a professional to unclog or fix a clogged fuel injector or components that may need replacement.
How to create your own homemade fuel injector cleaner
Commercial fuel injector cleaners are made up of 80-90% Kerosene or paraffin and 10-20% solvents such as acetone. You can make your fuel injector cleaner using these ingredients and use half a pint or 250ml every 3000 miles.
You can adjust the ratio as needed and see what works best for your car. However, this may not be a viable option. Especially if the ingredients used are not 100% pure. Fuel injectors cleaners are inexpensive, and you a better off spending a few bucks than messing up your car.
When is replacing your fuel injectors the only option?
In some cases, not amount to fuel injector cleaners can save them and all that is left to do is replace them. Driving with a bad fuel injector will not only affect how the vehicle performs on the road, but it may also damage the vehicle further even when the car is not in use.
Additionally, the injectors may affect fuel economy, car idling, and potentially a fire in case of a leaking fuel injector. Here are some common scenarios which require immediate fuel injector replacement;
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Increase or Decrease in Fuel Trims
The vehicle’s PCM adjusts both short-term and long-term fuel trim to compensate for variances in fuel pressure and fuel delivery to maintain the correct air/fuel ratio. Malfunctioning fuel injectors may throw the PCM’s built-in adaptive fuel control strategies causing it to miscalculate the fuel trims.
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Not Enough Resistance
This can only be determined by using an Ohm meter to check resistance to the fuel injectors. As shorts, opens, or excessive resistance in the injector solenoid can also cause problems. Excessive current flow will also cause the PCM injector driver circuit to shut down, killing any other injectors that share the same driver circuit.
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Longer Crank Times
Crank times longer than 5-seconds indicate damaged fuel injectors as they cannot build fuel pressure to the “threshold” within the anticipated average crank time. Leaking fuel injectors cause the fuel rail to lose pressure. This, in turn, leads to a longer than average crank because the rail will need extra time to pressurize.
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Failed Balance Tests
This is determined by performing an injector balance test, which helps to isolate the damaged fuel injector. The most effective way to perform this test is by measuring the pressure loss in the fuel rail when each injector is fired and pulses for a set period. This can be done using an electronic injector pulse tester.
Check this too: What Are The Signs Of A Weak Fuel Pump?
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Misfire Codes
In some cases, engine misfires may be caused by a clogged fuel injector. The misfire code may be a result of intermittent or suppresses fuel injection into the combustion chamber.
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Vehicle Won’t Start even with a Full Tank of gas.
This sign is a clear indication of failing fuel injectors, especially if you cannot find any other potential cause of the problems.