When you can’t start your vehicle, the first thing many of us do is reach for the jumper cables. They bail us out of quite a few situations, but what do you do when the car won’t start with a jump?
It can be frustrating and a little nerve-wracking, but with some guidance, we can help you figure out exactly what’s going on with your car.
We’ve highlighted nine potential causes for you here, and we came up with a thorough and comprehensive troubleshooting guide that will walk you through everything you need to know to troubleshoot and get to the root of the problem.
So, if your car won’t start with a jump, you’ve come to the right place. Just keep reading.
Causes of Why a Car Won’t Start With Jump
Before you can dive into how to fix your car, you need to know why it might not be starting in the first place. We’ve highlighted nine potential reasons you might not be able to start your car even after you hook up the jumper cables.
1. Damaged Battery
Many people tend to think that a jumper cable will always start your car no matter how dead the battery is. That’s not the case. If the battery is either damaged or completely dead, jumper cables might not provide enough of a boost.
If the battery is damaged, jumper cables will never work, but if the problem is a completely drained battery, you might just need to leave them connected a little bit longer to let the battery charge back up.
2. Inadequate Jumper Cables
Manufacturers don’t make all jumper cables the same. One of the most important things you need to look at when everlasting jumper cables is the size of the cable. This refers to the gauge of the cable, and the larger the gauge, the more effective the jumper cables should be at transferring power.
Ironically a smaller number gauge actually refers to a larger wire, so the best jumper cables have a smaller gauge number and larger wires.
3. Faulty Starter
While tons of people jump straight to the battery when their car won’t start, often the problem has nothing to do with the charging system. Your vehicle uses the starter to turn over either the flywheel or flex plate to start your vehicle.
If the starter isn’t working the way it should it doesn’t matter how much power you pump to it, the vehicle won’t start!
4. Faulty Neutral Safety Switch
Every vehicle has a neutral safety switch that keeps you from starting up your vehicle if you’re not in neutral or park. This component is the neutral safety switch, and it’s a great safety feature. But if it’s acting it up it might not recognize you’re in one of those two gears, and then you won’t be able to start your vehicle at all.
5. Faulty Fuel Pump
Your engine needs fuel to run, and it’s the fuel pump’s job to take fuel from the fuel tank and get it to the injectors. So if the fuel pump isn’t working, all the fuel will stay in the fuel tank and you won’t be able to get your vehicle to start no matter how much power you pump into the batteries.
6. No Fuel
Sometimes the simple answer is the best one. Your vehicle needs fuel to run, and sometimes you run out. And while you usually keep an eye on the fuel gauge to let you know when you need to fill up, keep in mind that this is a component that can fail on you too.
7. Clogged Fuel Filter
Many larger vehicles, especially diesels, have a fuel filter. While the fuel filter does a great job keeping contaminants from reaching the engine, the fuel filter can clog up over time. If it gets too far, fuel won’t be able to get past it and reach the engine, which will keep your vehicle from starting.
8. Faulty Spark Plugs
While this is unlikely to keep your vehicle from starting completely, it is possible. The only reason it’s unlikely to keep your vehicle from starting completely is because typically only one spark plug fails at a time, and your engine can still run without one.
But while the engine will run, you’ll get a check engine light and it’ll sound awful, which typically leads someone to fix the problem before it gets to the point where the engine won’t start at all. However, it is technically possible for a couple of spark plugs to fail at the same time, and this might keep the engine from starting.
9. Faulty Ignition Switch
When you turn the key or press the button in a push start vehicle, you’re telling the vehicle you want to start it up. But if there’s a problem with the ignition switch, the vehicle doesn’t know you’re trying to start it in the first place. If the vehicle doesn’t know you’re trying to start it up a jump start won’t do any good.
How to Fix a Car That Won’t Start With a Jump
With so many potential causes of a car that won’t start with a jump, it can be challenging to narrow it down to just one. We’ll do our best to walk you through everything you need to know and pinpoint the exact problem without the need to take it to a mechanic.
Your most important sense during this entire troubleshooting process is your hearing, so turn off any music or other sources of noise that might keep you from hearing your vehicle.
From there, go ahead and try to start your vehicle with jumper cables. You need to listen to what’s happening at this point. If the engine isn’t turning over at all, the problem can be the ignition switch or a neutral safety switch. But this is if you don’t hear anything coming from your vehicle.
During this process see if any of the electronics in the vehicle turn on when you have the vehicle in accessory mode. If they don’t, there’s a good chance the problem is the ignition switch. While it still might be the ignition switch even if the accessories come on, it’s more likely that the problem is the neutral safety switch.
If the vehicle is in park, try switching to neutral, and if the vehicle is in neutral, try switching to park. While this won’t always rule out a neutral safety switch, it’s a quick and easy way to rule out one of the potential problems with one.
If all you hear is a “clicking sound” the problem might be the starter, the battery, or the jumper cables you’re using. Give it a little time connected and try again. If it starts to turn over a little the problem is likely the battery or the jumper cables. At this point, we recommend taking the battery to a store like AutoZone to have them charge and test it for you.
Of course, if the engine sounds like it’s turning over more the longer you leave them connected, you can leave it connected for a while and eventually it should start up. Just keep in mind that it can easily take a few hours with smaller jumper cables.
And even then, if the vehicle has a parasitic draw or a faulty alternator, you might end up right back where you started in a day or two. Once you start up the vehicle, go ahead and take it to a place like AutoZone and they can check the entire starting and charging system for you for free.
However, if you hear the engine turning over just like it would when you would normally start it, you can likely rule out all of the above options. While it can still be the battery, if it’s turning over consistently when you try to start it, it’s unlikely that’s the problem.
Instead, there’s a good chance the problem is with the fuel system. Have someone stand near the rear of the vehicle near the fuel tank and see if they can’t hear the fuel tank kick on when you’re trying to start the vehicle.
If they can hear it, you know that’s not the problem, but if they can’t, that might be it. If your vehicle has a fuel filter, check it out, clean it, or replace it if necessary. Then ensure the vehicle has enough fuel to start. At this point, the problem might be the spark plugs, but we’d highly recommend ruling everything else out first.
How to Properly Jump Start a Car
Jump starting a car isn’t something most people do every day, so we also has to cover the possibility that you’re not jump starting correctly. Therefore, it’s always a good idea to have a refresher on the proper steps to make sure the jumper cables is connected the right way.
Also, make sure you have a good connection between the cable clamps and the attached surface or battery terminal. Here’s a few steps to properly jump start your car:
- Park the vehicles close together so jumper cables can reach both batteries.
- Locate the battery. (consult your car owner’s manual)
- Attach one of the red cable clamp to the positive terminal of the dead battery.
- Attach the other end of the red cable to the terminal of the working battery.
- Take the black cable and attach one end to the negative terminal of the working battery.
- Take the other end of the black cable and attach it to unpainted metal surface of the car with the dead battery – DO NOT ATTACH TO THE BATTERY ITSELF!
- Start up the car with the working battery and let it run for 5 to 10 minutes.
- Finally, start up the car with the dead battery.
- Remove the cables in the opposite order to which you put them on, i.e. the black cable first.
Final Thoughts
Now that you know a little more about why your car might not start even after you hook up jumper cables, all that’s left is for you to head out and start troubleshooting your vehicle.
With our guide at your disposal, we’re confident you’ll be able to get to the root of your problem in no time and potentially even save yourself a ton of money compared to taking your vehicle to a professional mechanic!
