If your car battery is drained flat or aging, with a set of jumper cables connected right and a helpful neighbor with a charged battery, you jumpstart your car successfully almost all the time
Well, “almost all the time” because in a few cases, your car’s engine may stop after jumpstarting it and getting the engine running, it dies when the jumper cables are removed.
This may be after a minute or so of running. Whichever the case, getting the car fixed and up and running again is always of priority.
So, in this post, I’ll share some helpful tips on how you can fix your car should it cut off including checks you can do, share reasons why your car my be cutting out when the jumper cables are disconnected, and also provide tips to prevent your car engine from cutting out after jumping it.
Quick answer: If your car (with a flat battery) cuts out shortly after a jump start, when the jumper cables have been removed, then it’s likely a problem with the alternator or battery not being able to power the car’s electrical system.
A good place to start is to check the alternator and battery connections to confirm that they have no corrosion and are firmly connected to rule out any loose connections
Read on for what other checks you may need to do to stop the car from cutting out after removing the jumper cables.
Tips to Fix a Car engine that Stops after Removing the Jumper Cables
Let’s dig deeper into what can go wrong with each and what checks you should do to locate and fix the fault.
#1. Check the alternator voltage output and firmness of cable connections. An alternator that is faulty – no electrical power or low voltage, or one that is not able to power the car’s electrical system will cause the car engine to stop (if the battery voltage is low).
If the alternator cables are loose, damaged or the fusible link has blown then no electrical power will flow to the car’s electrical system to keep the car engine running.
Checks on the alternator: The most reliable test is to have it bench tested and (on load) to confirm that it is able to power the car’s electricals reliably.
As an interim step, you can measure the voltage at both the battery terminals and at the alternator. With the engine running at idle, the voltage should be in the 13.5 -14.5V range.
If it is significantly lower than that then you might have a fault in the wiring or with the alternator. Get the car’s alternator tested at a car repair shop.
You may also be interested in this post: What shows that the alternator brushes are worn?
# 2. Check the battery condition. If the battery is damaged or flat, with some cars, even with a good alternator, the car engine will stop running as soon as the jumper cables have been removed.
This is because the damaged battery can suck up all the alternator power starving the rest of the car’s electrical system of electrical power that is necessary to keep the engine running.
Checks: Fully charge the battery using a car charger and then attempt to start the car to see if the car engine keeps running.
You can also take the car battery to an auto repair shop to confirm the condition of the battery before you invest in a replacement.
You may also be interested in this post: Can a bad battery cause computer problems?
#3. Confirm that alternator and battery cable connections are intact and firm. A car engine can also cut off if the alternator or battery connections are weak or loose.
Remove any corrosion on the battery terminals and make sure they are clean and firmly connected to the battery posts.
Also, confirm that the alternator plug is firmly connected.
Additionally, you can also measure the voltage at the alternator output terminal first and then at the battery positive terminal next and compare the two.
The voltage should be the same if the cable between the alternator ad the battery is intact. If not, inspect the cabling for any loose or damaged sections and repair accordingly.
Testing the Car’s Ground Connection
You can also measure the voltage with the positive probe of a good quality meter connected to the battery positive and the negative, first at the negative battery post and then at the engine block.
The voltage should be the same. A difference in the voltage indicates a break in the ground cable.
Note: It is possible for the ground cable to appear intact on the outside when it is damaged on the inside.
#1. Why your Car engine may Keep Cutting off after Jumper wires are Disconnected?
If the car engine keeps dying after removing the jumper cables, then the underlying problems related to the car’s electrical system -alternator, battery, or cabling have not been resolved.
Work through the suggestions and also do not hesitate to contact a qualified car mechanic.
# 2. How Long to leave Car Jumper cables Connected?
Leaving the car jumper cables connected for about a minute after the car with the flat battery has worked successfully for me over the years without any damage to either car’s alternators and batteries.
That said, some car repair shops suggest leaving the car running for as long as as 5 minutes while others suggest that as soon as the car engine starts, the jumpers should be disconnected to protect the battery.
Can the Order of Removing the Jumper Cables cause the Car engine to Stop?
The order of removing batteries cables should not result in the engine dying provided the car engine has started and there are no underlying problems with the car’s electrical system.
The recommended order of removing jumper cables starting with the negative terminal is intended to avoid accidentally shorting one of the batteries in the event that the positive clamp touches the chassis.
Removing the positive clamps first instead of the negative increases the risk of a short-circuit, and arc should it touch the car’s chassis
Order of Connecting and Disconnecting Jumper Cables.
Order of Connecting Jumper cables
- For the car with a good battery, first, connect the red (positive) clamp of the jumper cable to the positive battery terminal (marked with a + sign).
- Connect the second red clamp of the jumper cable to the positive battery post of the dead battery (marked with a + sign)
- Next, connect the black clamp to the negative post (marked – sign) of the good battery.
- Finally, connect the second black clamp of the jumper cable to the exposed, unpainted part (inside the hood) of the car with the dead battery.
Allow the dead battery to charge for about 5-10 minutes and then attempt to start the car with the dead battery.
The car engine may not start on that first attempt. Allow for another 5-10 minutes and try to start again.
It should start normally on the second attempt.
Let the car engine of the car with the dead battery run for about minutes to charge some more and then disconnect the jumper cables in this order.
Order of Disconnecting Jumper cables
- First, disconnect the black clamp of the jumper cable from the exposed, unpainted part (inside the hood) of the car with the dead battery.
- Next, disconnect the black clamp from the negative post (marked – sign) of the good battery.
- Then disconnect the red clamp of the jumper cable from the positive battery post of the dead battery (marked with a + sign)
- Lastly, disconnect the red (positive) clamp of the jumper cable from the positive battery terminal (marked with a + sign) of the good battery.
- Drive the car which had a drained battery for about 15-30 min to top up its char
Tips to Prevent your Car from Cutting Off when Jumper Cables are Removed
To avoid the car cutting out when the jumper cables are removed, make sure that the battery and alternator connections (including the battery ground) are clean (all corrosion is removed), and firmly fixed.
This reduces the risk of the car dying out because the alternator or battery power can’t get to the car’s electrical system.
If the battery is deeply discharged, charge it first using a battery charger to prevent all the alternator’s electrical power from being sucked up by the battery.
Additionally charging deeply discharged batteries with a car alternator also applies a lot of stress to it and can damage the alternator.
if your car is cutting out after jumpstarting then there is likely a problem with the car’s alternator, battery, electrical system wiring, or a combination of them.
If you have the skills, you can trouble-shoot yourself or alternatively have the car checked out by a qualified auto mechanic.