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Jump Start Failed? The A – Z of why your car won’t jumpstart

Written BySteve Riley Updated on25/07/2022

The a – Z of Why Your Car Won’t JumpstartHaving a dead car battery is no…

jump-start-failed-the-a-z-of-why-your-car-won-t-jumpstart

The a – Z of Why Your Car Won’t Jumpstart

Having a dead car battery is no cause for alarm, especially when a quick jumpstart is all you need to fix the problem. But, sometimes your car won’t start even with jumper cables and in this article we explore some of the reasons why.

Table of Contents
  • The a – Z of Why Your Car Won't Jumpstart
jump-start-failed-the-a-z-of-why-your-car-won-t-jumpstart

The simple reason why your car won’t jumpstart even with jumper cables is that the circuit wasn’t complete. This could be due to several factors, either your jumper cables were connected wrong, or your battery terminals are corroded, and electrical current cannot reach the dead engine. Either way, if you don’t see a spark when connecting the last cable onto a metal bolt on the engine, know your jumper cables aren’t working effectively and here are some reasons why.

Corroded battery terminals

The Presence of a white chalky substance or green residue on your battery terminals indicates corrosion. The latter impedes the flow of electrical current and could be the reason why your car won’t jumpstart. You will therefore, need to scrape off any residue found on your battery before attempting to restart your engine. Also, check to see if your cables alligator clips are rusted as this affects their ability to allow electrical current to pass through.

Jumper cables are connected wrong

Jumper cables need to be hooked up correctly for them to restart a dead battery. If the jumper cables are loose or not connected to the right terminals, the battery will not start up, and you could permanently damage your vehicle engine. To avoid this, you will need to follow the safe connection process outlined below.

First, you need to find a car with a working battery that has a similar voltage to your own. Park it close to your vehicle but make sure there is enough space between them so that they don’t touch. Then take the red cable and clamp it on to the positive battery terminal on the ‘working’ vehicle before clamping the other end to the positive terminal on your dead battery.

Once this is done, take the black cable and clamp it onto the negative terminal on the ‘working’ car battery before attaching the other end to any unpainted metal block on the dead engine. Start the working vehicle and let it run for a few minutes; this will allow the dead battery to charge up first increasing your chances for a successful restart. After a few minutes start your car to see if it will pick up.

Note, once the dead battery has come back to life, you will need to disconnect the jumper cables in reverse order.

Not enough charge

Sometimes the car battery can refuse to jumpstart right away because it is completely drained. You will need to let your battery sit idle and charge for a while before attempting to restart it successfully. It also helps if you ask the person in the working vehicle to rev up their engine to facilitate this process. So there should be no immediate cause for alarm if your vehicle doesn’t immediately start up once you’ve connected the jumper cables. Especially if your battery has been dead for a couple of days, let it sit connected for up to five minutes before starting your engine.

Your anti-theft system may be interrupting the power supply to your vehicle

As a safety measure to ‘suspicious’ activity, which in this case is the jump start attempt, you can disengage it and attempt the process again. This can be frustrating for second-hand car users who are dealing with a security system that was installed by the previous car owner and are unaware of the disengaging process. In such cases, you can ask your local mechanic to do away with the system altogether.

Gauge

The size of your jumper cable matters. Jumper cables with smaller gauge numbers have thicker wiring. Thicker wiring can transmit a more substantial amount of electrical current to the dead engine giving it the juice it needs to jumpstart. If your jumper cables have a gauge rating of 10 or 8, they will not be able to jumpstart a full-sized car or diesel engine. They are designed to carry enough power for compact and subcompact vehicles. A 1-6 gauge jumper cable carries more than enough current to start any engine and have longer cables.

Worn out battery wires and dead cells

Depending on the type of car battery you have, the presence of a dead cell within your battery will result in an unsuccessful jumpstart. Also, some batteries have a small wire hooked to its internal connectors. Sometimes this wire breaks or gets so worn out that the circuit cannot be completed and is the reason why your jumper cables aren’t sparking.

It’s not the battery

More often than not, we misdiagnose the issue, and the inability of your car to start may have nothing to do with your car battery. You will therefore, have to invest in a multimeter since it can be used to check whether your jumper cables are working, by measuring the voltage of the car being jump started. If it reads anywhere near 14 volts, then your jumper cables and battery are working fine and are not the issue. Using jumper cables in such a case will not work and here are some of the reasons why.

Worn out spark plugs

Always check on the state of your spark plugs and replace them after 100,000 miles since they can affect the running of your engine and cause a no-start.

Empty fuel tank

There are instances when the fuel gauge malfunctions and provides an incorrect fuel reading. Your car may be refusing to start because your fuel tank is empty. Try fueling your car to see if it’ll start up.

Clogged fuel filter

A clogged fuel filter needs to be replaced because it will restrict fuel flow. You can find out if it’s functioning properly by removing it and try passing air through it successfully.

A poorly functioning alternator

If you have a bad alternator, the battery will not get charged even after letting it sit connected to the jumper cables and revving the engine for a few minutes. The car will jumpstart but die immediately after disconnecting the jumper cables.

The tell tale signs of a car battery going dead

Any time that you are driving a car you need to pay close attention to how it behaves and look out for anything that you might have never seen before.

The warning lights

If your battery is weak then you will see a warning light on the dashboard, most cars will display a battery symbol, and if goes on abruptly while you are driving, don’t panic and switch off the car instead keep driving until you get to your destination. If it gives you trouble when starting, once it goes on don’t switch it off, at least until you reach your destination.

Oil change

New drivers need to take this point seriously, whenever you get your oil changed ask request for a complementary battery test. The results will tell you whether you need to get a new battery to avoid getting stuck. Therefore, if your car battery is over seven years old and the results show that it is underperforming then you might have to replace it.

Check for crusty connections

Having a car is like taking care of a small baby because it wont tell you why it is crying so you have to keep guessing, but the good thing with the car you can carry out occasional checks to ensure that there aren’t any abnormalities. For example, some battery posts might seem corroded and if you notice this in your car then best you clean it up because your car might fail to start.

Difficulty in operating other car features

So this might actually be stressful but if it happens it is for the best because then you will know what to do. Anytime that your power windows have difficulty opening or closing, just know you are developing battery problem, also if your experiencing problems with your radio then just know that your battery is the cause.

Frequently Asked Questions (FAQ)

Can you ruin your car by helping others jumpstart?

When helping a friend to jump start their car, both cars are in danger because there is the risk of overvoltage, which will negatively impact any electronic equipment, including the headlights because they are normally on during this process.

What shouldn’t I do when jump starting a car?

For starters if you have never jump start a car, then don’t best you call a professional, but if you have the knowledge then put on some protective clothing. Also be sure to use good quality cables to jump start your car.

How do I know when my car battery needs replacing?

If you have been driving a car for a while then you are familiar with how fast it starts when you want to leave, so the moment you experience a slow engine crank or rather if your car takes longer to start then it might be time to hit the stores and get a new battery.

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