Connect battery up to car, car then tries to start by its self without key in ignition. What can be problem
My car has 141000 miles.
My car has an automatic transmission.
How to Identify and Fix Common car Problems ?
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The most common reason cars don`t start is a dead or faulty battery. Even though most cars run on gasoline, they all require electrical power to function. The starter that cranks your engine to start requires an electrical signal to fire.
If you have a good battery and enough fuel in the gas tank and your car still won`t start, chances are you have a bad spark plug. Why? A bad spark plug will prevent fuel ignition, and the vehicle won`t move.
One common culprit for this problem is the crankshaft position sensor, which measures the position and speed of the crankshaft. The computer uses the information from this sensor to know when to fire the spark plugs. If the sensor isn`t working, the spark plugs won`t fire, keeping the engine from starting.
When the starter relay is switched by the ignition circuit, it powers up the starter solenoid. A trigger wire initiates the process where the starter begins its job.
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If your vehicle is under warranty, by law the dealer MUST repair the issue you are describing within a prescribed time frame and number of "attempts", otherwise the dealer will run afoul of Federal and state Lemon Laws that give you very specific rights, and recourse (contact an Attorney; we are Mechanics, NOT attorneys). Consequently, if the vehicle is still under warranty, to save yourself money do be sure to seek a resolution from the dealer. If the vehicle is not under warranty, obviously a certified Mechanic from YourMechanic could identify the electrical fault and resolve this for you. If you want to go that route, please simply request a no start diagnostic -electrical system and the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
If you recently replaced your battery, the issue may be caused by a malfunctioning alternator or other electrical component that comprises the charging system on your Nissan Sentra. The best way to find out which item specifically is faulty, is to have a professional mobile mechanic complete a car is hard to start inspection. This will allow the mechanic to determine the precise source of what’s going on with your Sentra and recommend or complete the right repairs.
If the key is stuck in the start position, this is a ignition lock cylinder issue and the reason the starter continues to turn the motor over. If the starter is turning but the motor is not, then the starter is likely the problem. Either that or the teeth on the flex plate are all gone. This would require removing the transmission to repair.
If the car runs intermittently, this can be a big challenge. And it also means the starting system is working. It will need to be diagnosed when it is failing. A working car cannot be diagnosed because there is nothing wrong. Where you park your car should not have any affect. It certainly could be a wiring problem. Wiring problems hide really well and can happen anywhere in the miles of wires that are in your car. Isolating the system that is failing is really important here. At the moment I am unsure which system is failing. Starter system, ignition lock cylinder and or ignition switch electrical or something with the engine control system.
When the car is failing, you need to check for spark and fuel pressure. If neither is present, this is a clue. Usually the crank sensor will do this. Does your car have a tachometer? If so, does it move at all when cranking. This is a clue whether or not the cam and or crank sensor is working. Is there a Check Engine Light on with the key on? If there is a Check Engine Light, the code or codes can be used for specific diagnosis.
All of these concerns will send you down a diagnostic path. Be sure not to confuse yourself by misinterpreting multiple system failures. If the key does stick in the start position, this would be the first problem to solve. After that, does the motor actually turn when the starter turns? After that, the question of "Why won’t it start?" is first answered by finding what the motor is lacking. Fuel, spark etc… Good luck.
If you need assistance with these checks, contact a certified mechanic who has the tools and experience needed to properly diagnose this starting issue with your car.