Mercedes Mullins
If your car won't start, but you can hear the fuel pump humming, there could be a few potential issues at play. One possible explanation is that there may be an issue with the camshaft sensor or weak spark from the coils, preventing the injectors from turning on. Another possibility is that the fuel pump is not providing sufficient pressure and volume to start the engine. In some cases, it could be related to the power steering pump fluid or a broken transmission cooler line, especially in heavy-duty trucks. It's recommended to have the computer tested for cam or crank sensor codes and to check the fuel pressure to pinpoint the exact cause.
Characteristics and Values
| Characteristics | Values |
|---|---|
| Car won't start | Fuel pump is humming |
| Starting fluid in air intake helps run for a few seconds | |
| Car tries to start without starting fluid | |
| Computer test for cam or crank sensor codes | |
| Injectors may not be turning on due to camshaft sensor or weak spark from coils | |
| Check fuel pressure to ensure pump is providing enough pressure and volume |
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What You'll Learn
Check the camshaft sensor and spark coils
If you can hear the fuel pump but your car won't start, one of the components to check is the camshaft sensor. The camshaft position sensor is crucial for the engine to run properly. It is responsible for checking the timing and throwing a code if it is off. It also helps identify which cylinder is firing.
To check the camshaft sensor, you can perform a quick test to see if there is a spark. If there is no spark, the sensor may be faulty. The PCM (Powertrain Control Module) will shut down the spark if the sensor inputs for crank timing are not correct. Messing with the sensor could also result in bad wiring. The sensor should be as close as possible without making contact, and the angle change can affect the logic pulse strength.
In addition to the camshaft sensor, you should also check the spark coils. The ignition system should deliver a strong, bright blue spark that can jump at least half an inch of a gap while cranking the engine. To test this, access the wire or coil and insert a spark tester or screwdriver, grounding the other end. Watch for the blue spark while cranking the engine.
If there is no spark, it could be due to a blown fuse or relay. Some vehicles use an ignition module, while others are triggered directly from the engine computer but still need a separate power source for the ignition coils. Additionally, a base engine mechanical issue could cause the valve timing to be off, affecting the spark.
By checking the camshaft sensor and spark coils, you can narrow down potential causes for your car not starting, even though you can hear the fuel pump.
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Test the computer for cam or crank sensor codes
If your car won't start, you can test the computer for cam or crank sensor codes by checking the engine RPM signal from the crankshaft sensor using a scan tool. If you don't see an RPM signal when cranking the engine, disconnect the crankshaft sensor and, with the key on, check for a 5-volt reference signal, the ground connection, and ensure the signal return circuit isn't showing any voltage with the sensor disconnected. If you don't see the 5-volt reference or the ground, re-check the continuity of the wires back to the computer to ensure nothing has broken.
You can also check the inputs from the camshaft and crankshaft sensors using a scan tool. If you're getting a P0340 code, it could mean one or more of the following:
- A wire or connector in the circuit is grounded, shorted, or broken
- The camshaft position sensor has failed
- The PCM (Powertrain Control Module) may have failed
- There is an open circuit
- The crankshaft position sensor has failed
If you're getting a P0343 code, it could be related to the timing belt and camshaft position sensor. Additionally, a P0446 code indicates an issue with the evaporative emissions purge valve electrical circuit.
It's worth noting that some engines, like the SPI and SVT, require a cam sensor to run, while others, like the Zetec, can run on just the crank sensor. If the cam and crank sensors are not in agreement, the car may not start.
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Check fuel pressure to ensure the pump is giving enough pressure
If you can hear your fuel pump but your car won't start, one of the possible issues could be low fuel pressure. Checking the fuel pressure is a straightforward process and can be done at home. It is important to be cautious when performing this task, as releasing fuel under pressure can cause fires and injuries. Therefore, safety precautions such as wearing safety glasses and gloves, working in a well-ventilated area, and avoiding smoking or any potential sources of sparks are crucial.
To check the fuel pressure, start by parking your vehicle and engaging the parking brake. Allow the engine to cool down to ensure your safety during the process. Once the engine has cooled, locate the fuel pressure test port, which is usually located near the fuel pump. Place a rag under the test port to catch any fuel that may be released during the testing process.
The next step is to install a pressure tester onto the test port. You may need tools like a screwdriver, ratchets, and sockets for this step. After the pressure tester is securely installed, start the engine and let it idle. Refer to the manufacturer's manual for specific instructions, as some manufacturers recommend checking the pressure with the engine running at a particular RPM.
Finally, record the pressure reading on a fuel pressure gauge. Compare this reading to the manufacturer's specifications to determine if the pressure is within the acceptable range. If the pressure is low, it could indicate an issue with the fuel pump not providing sufficient pressure, which may require further troubleshooting or repair.
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Try using starting fluid in the air intake
If your car won't start but you can hear the fuel pump, one thing you can try is to use starting fluid in the air intake. This method has been tried by some car owners and has shown to have some success, with the car turning on for a few seconds.
To do this, spray starting fluid into the air intake of your car. This method will help you determine whether the issue is related to the fuel system or another component. If your car starts momentarily with the help of the starting fluid, it indicates that the fuel system is likely functioning properly, and the issue may lie elsewhere.
However, it is important to note that this is not a permanent fix and the car will likely shut off after a few seconds. The root cause of the issue could be related to the camshaft sensor or weak spark from coils, which may require further diagnosis and repair. Additionally, you should check the fuel pressure to ensure that the pump is providing enough pressure and volume.
It is always recommended to consult a professional mechanic to properly diagnose and repair any issues with your vehicle. They will be able to run a computer test to check for any error codes and provide a more comprehensive solution to the problem.
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Let the car sit for a few days
If your car has been sitting for a few days and won't start, there are a few potential issues that could be causing this problem.
Firstly, check the battery. Even if the radio and lights turn on, the battery may not have enough power to start the engine. This is a common issue if your car has been sitting for a while, as the battery will slowly lose its charge over time, and attempting to start the car will drain it further. Try jump-starting the car to see if this is the issue. If jump-starting works, but the car still won't start normally, you may need a new battery.
Another potential issue is that animals may have made their home in your car, especially if it has been sitting in one place for several days. They may have chewed on wires or damaged other components, preventing the car from starting. Check under the hood and around the engine bay for any signs of animals or damage they may have caused.
Additionally, if your car has been sitting with fuel in the tank, the gas could have degraded over time, especially if it was not full when you left it. Old or contaminated fuel may fail to ignite, causing the engine to crank but not start. Try adding some fresh, high-quality fuel and see if that helps.
It is also possible that the tires have slowly lost air pressure while the car has been sitting. This is especially common in cold weather. Check the tire pressure and inflate them if necessary before attempting to start the car and drive.
Finally, if you haven't driven your car in a while, it's a good idea to take it for a longer drive on a highway rather than just around the block. This will help ensure that all the systems get properly warmed up and circulated, which is important for the long-term health of the car.
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Frequently asked questions
You may not be getting the injectors turning on due to a camshaft sensor or a weak spark from the coils. Get your computer tested to see if you have cam or crank sensor codes.
Check your fuel pressure to see if the pump is giving enough pressure and volume.
After the computer test, the codes can be diagnosed and then addressed accordingly.
There could be a number of reasons for this, including issues with the fuel pump, battery, ignition, or engine. It is best to consult a mechanic to diagnose the exact issue.
