5 Signs of a Faulty Cold Start Injector

hands holding spraying fuel valve in engine
  • 1-2 hours
  • Intermediate
  • $40-200

If your car is having issues starting, it may be signaling a faulty cold start injector. The cold start injector, also called a cold start valve or sensor, is a part of the vehicle that helps an engine start in cold temperatures. The sensor is part of the cold air intake in an engine, and works by injecting fuel into the air mixture when it is too cold to start through normal fuel delivery, and is controlled through a thermal time switch.

Older cars, and small engines found on equipment such as lawnmowers, use a choke to deliver the extra fuel needed to start engines in colder weather, but almost all modern cars use the more efficient cold start valve connected to the car's computer system.

Among the signs of a faulty cold start injector are difficult starts, no start at all, engine flooding, and start/stop issues when running your car. Learn more below about the five signs of a faulty cold start valve and how to replace the valve when the time comes.

1. Difficult Start - Delay and Hesitation

The cold start valve’s purpose is to inject additional fuel into the engine on cold days. A sensor reads the temperature when you try to start the car.

If the sensor or the valve are faulty, your car may have a difficult time starting when the temperatures drop. The car may act like it’s not getting enough gas. So it will turn over, but not fire up.

If the cold start valve is set to run for too long, your car will hesitate in starting and crank for a long period of time before running normally after finally heating up. You may be able to make an adjustment, or you may have to replace the part. Try reducing the thermometer start interval to between 2 and 5 seconds while troubleshooting the issue.

engine fuel valve injector

2. Engine Does Not Start at All

Sometimes the problem of a faulty cold start valve prevents the engine from starting at all. This typically happens when the cold start valve is clogged, preventing fuel from releasing into the engine. Without that burst of fuel, the engine may refuse to start.

While you may be able to locate and unclog the valve, it may be time to replace it for a new one.

3. Engine Floods When Trying to Start

Another symptom of a faulty cold start injector is an engine that floods when you attempt to start it. In contrast to the previous problem where fuel is restricted, a flooded engine indicates a leak of too much fuel into the system.

When this happens, you’ll likely be able to smell the fuel and your exhaust may be dark.

Sometimes the engine will start after allowing it to rest for several minutes in between attempts, but if the cold start injector is continuously or intermittently injecting too much fuel, it’s an issue you’ll need to address right away.

4. Engine Starts and Then Stops

A car with engine issues can act strangely at different times. If your vehicle fires up, but then dies, a faulty cold start valve may be the issue. The vehicle may even run for a while before you incur problems. For example, it can suddenly die when you come to a stop, or stall while you drive. It may be most noticeable at high RPMs, or it might take place when you release your foot off the gas pedal.

An adjustment to the cold start injector might do the trick, or a full replacement may be in order. However, extreme car engine issues such as this are not only a safety hazard, but also could indicate a bigger issue with the engine system.

5. Engine Smokes When Started, Then Stops

If you notice a dark exhaust in conjunction with any other symptom, it’s likely the cold start valve is to blame.

Take it as a sign your system is running too rich and start looking into how to go about replacing your cold start injector either by installing a new part yourself or by going to your local auto mechanic.

How to Replace a Cold Start Injector

If your car is exhibiting any of the above signs, it may be time to replace your cold start valve. Start by checking your owner's manual for the exact part you will need as cold start injectors can vary widely between car make and models.

The price for a cold start injector car part can vary widely, starting below $40 to upwards of $200.

Below are tips on how to make the replacement on your own. Review the steps before deciding if you'd like to save money on a repair yourself or if you need to go to an auto mechanic.

Step 1 - Use Your Repair Manual

Replacing the cold start valve can be a little bit tricky. There are some steps in the process that may be easily overlooked. Be sure to carefully read through a repair manual on your specific vehicle.

The manual is the best resource for finding the location and function of the cold start valve specific to your engine's unique system and layout.

Step 2 - Locate Cold Start Valve

fuel valve in gloved hand

In most makes, the cold start valve will be located within the air intake distributor. Remove the air intake cover and the air filter.

You should notice a small valve that looks like a fuel injector within the assembly.

If you have problems locating the cold start valve, refer to the specific repair manual for your engine or see if YouTube can help you out for your exact car model.

Step 3 - Disconnect the Car Battery and Valve

Using a ratchet or the appropriate wrench, loosen the bolts on the battery terminals. Remove the battery terminals and set them in a safe area.

Set up a drop light to illuminate the work area. Many car hoods have a hook where you can hang a work light or you can ask a friend for help. Disconnect the electrical lead from the outside terminal of the cold start valve.

Use a screwdriver to gently pry the plastic tabs around the valve. Then pull the wiring harness out from the valve.

Step 4 - Remove the Cold Start Valve

fuel injection valves

Look for small screws holding the cold start valve to the air intake assembly. Remove the screws very carefully as they can easily break from too much pressure.

Use a magnetic screwdriver to keep from losing the screws. Once they are removed, unscrew the cold start valve from the fuel rail.

Step 5 - Install the New Cold Start Injector

Use a clean shop rag to clean out the threads and surrounding area. Set the new valve in place and screw it into the fuel rail.

Connect the wiring harness to the valve and replace the battery terminals. Turn the key to 'On' to let the fuel pump run before starting the engine.

Although there are other causes for engine hesitations, rough starts, and dark exhaust, if you’re experiencing these issues, a faulty cold start injector is a common suspect. Read up on What to Do When a Cold Engine Is Hard to Start for more information on other common car engine problems.