If the car does not start, the problem could be lurking in several places. The first three things you should check are the starter motor and battery, fuel supply and ignition - one of these is likely to be responsible. Begin to narrow down the possibilities to understand what to do to fix the vehicle.
Steps
Method 1 of 3: Check the Starter Motor and Battery
Step 1. Listen to the sounds made by the vehicle when you try to start it
When the engine doesn't start, the easiest problem to diagnose is a dead battery. When you turn the ignition key, listen to the sound emitted by the engine; if you hear nothing, the battery may simply be "dead".
- If you hear a "click", it could be a sign that the starter is trying to crank but is not receiving enough power.
- If the engine runs but fails to start, the problem is likely not with the battery.
Step 2. Check the battery terminals
Open the hood and inspect the cables connecting the accumulator to the engine. There are two poles (one negative and the other positive) and for both the connections with the cables must be clean (metal to metal), so that enough electrical energy can be transmitted; check that both cables are connected and that the terminals are not covered by debris or oxidation material.
- Use a steel bristle brush to clean the corroded battery posts.
- Check that the clamps are tightly tightened around the cables and that the cables have no play or detach from the battery.
Step 3. Test the battery
Once you are sure the cables are in order, use a voltmeter to detect the potential difference in the battery. Turn on the instrument and connect the probes to the positive (red) and negative (black) pole of the accumulator; if the battery is charged, you should get values between 12, 4 and 12, 7 volts.
- If the battery is dead, try to start it with the jump leads.
- If it cannot hold the charge, replace it and try starting the car again.
Step 4. Try to start the engine with the jumper cables
If the wiring is properly connected, use another vehicle to start the car; join the two batteries, making sure you have connected the positive poles with the red cable and the negative ones with the black cable.
- Check that you have correctly connected the cables to their respective poles, otherwise you could cause serious damage to the vehicle.
- Some motors are equipped with a main fuse inserted in the system immediately after the battery and which blows if the cables are mistakenly reversed; if you break the fuse, you need to buy a replacement.
Step 5. Inspect the starter relay
If you are unable to start the engine with the jump leads, there may be a malfunction in this device. Run a test with a phase finder; touch the lower terminal of the relay with the phase detector and connect the negative cable to the vehicle body for grounding. Ask a friend to try starting the engine to see if the relay activates.
If nothing happens, the device is damaged and needs to be replaced
Method 2 of 3: Verify Engine Is Getting Fuel
Step 1. If the tank is empty, add gasoline
If the fuel level is very low, top up using a specific red plastic tank to transport and pour the gasoline. This substance is able to corrode several different types of plastic materials, it is therefore essential to use a special container; screw the spout onto the large opening of the tank and open the vent cap on the other side before pouring the liquid into the tank.
- The breather cap allows air to enter the tank and therefore to release the petrol that falls back into the vehicle's tank.
- Be careful not to splash fuel on your pants or skin.
Step 2. Pay attention if the car jolts as you drive it and before it shuts down completely
A classic symptom of fuel tank problems is jerky or unpredictable movements that occur while driving the car at a constant speed, such as on the highway. If you find that the engine power is unstable even though you always keep the same pressure on the accelerator, there could be problems in the supply of gasoline.
- If you also notice a drop in RPM as the engine loses power, there is a problem with the fuel.
- If the revs increase when you feel a drop in the power transmitted to the wheels, the cause is usually attributable to the transmission.
Step 3. Try again after a few minutes to see if the engine restarts
If the car stops while you are driving and has difficulty starting or running immediately afterwards, wait a few minutes before trying again; if the engine starts running after about 20 minutes, there may be a blockage in the fuel filter.
- As sediment builds up on the filter, it can completely clog it and prevent fuel from flowing to the engine.
- When the filter has a chance to rest for a few minutes, the sediments settle, restoring the gasoline flow.
Step 4. Change the fuel filter
The engine may not be receiving enough power due to a completely clogged filter; replace it after locating it in the underbody and disconnecting the fuel inlet and outlet pipes. Remove it from its holder and insert a new one, to allow the gasoline to flow further towards the engine.
- You can buy a new one in the auto parts store.
- When the filter is severely clogged, it can cause the fuel pump to burn out.
Step 5. Inspect the fuel pump
There are two methods you can follow for this test to verify that the element is working properly; be sure to check it is receiving electricity and run a flow test to check the volume of fuel being sent to the engine.
- If the pump is not working properly, you need to replace it.
- Consult the operation and maintenance manual for specific instructions for changing the fuel pump.
Method 3 of 3: Check the Starting System
Step 1. Inspect the spark plugs for damage
Use a specific compass for removing these elements and observe them to understand if they are the source of the problem. Disassemble each spark plug and inspect it for specific types of damage that might make you understand why the engine won't start.
- If the terminals are brown or gray, they are in good condition.
- Black or burnt spark plugs are a sign of too much gasoline in the engine.
- The presence of bubbles indicates that the engine is overheating in a worrying manner.
Step 2. Replace the spark plugs if necessary
If they look dirty and malfunctioning, you need to address the underlying problem that made them so, to make sure the engine is operating at peak performance; once the issue is resolved, replace the damaged spark plugs with new ones.
- Adjust the gap of the new spark plugs, based on the type of engine in the vehicle.
- You can find the specifications regarding the distance of the electrodes in the vehicle owner's manual.
Step 3. Check the spark plug leads
Make sure they are all well connected to the spark plugs themselves and to the ignition coil. You can use an ohmmeter to test the resistance of the spark plugs and verify that they are receiving enough from the wires to ignite the mixture of air and fuel inside the engine.
- Check that the cables are not damaged, for example that they are not frayed or broken.
- Replace any that show obvious signs of wear, even if they are not responsible for the engine malfunction.
Step 4. Test the ignition coils
Although it is quite unlikely, if all the coils fail, the engine will not start; test by removing a spark plug and re-connecting it to its cable. Touch a piece of metal in the engine compartment with the spark plug electrode and ask a friend to turn the ignition key.
- If the coil is OK, you should see a blue spark coming out of the spark plug.
- Repeat the test for each spark plug in the engine.
