Your Jeep won’t start and you think it is because you left a light on overnight. That could definitely run the battery down and keep the Jeep from starting in the morning. Most Jeeps, and other vehicles for that matter, need about 9-10 volts of battery charge to start the Jeep up. We will assume the battery isn’t too old (maybe a 1-3 years) and that it is a negative grounded battery. It is time to learn and fully understand the process of jump starting a Jeep.
How do you jump start the Jeep? Jump starting a Jeep, or any other vehicle for that matter, is a relatively easy process. However, the jump start process needs to be done in a very particular order and will require another vehicle or a battery boost pack to do the charge and jump start. Jump starting a Jeep should take about 10-15 minutes to perform the entire task.
Here’s What You Will Need to Jump Start Your Jeep:
- A booster battery (essentially another working vehicle or a battery charge pack)
- Jumper cables in good condition—no cracks or exposed copper wire
Here’s What to Do to Jump Start Your Jeep:
- Move the booster vehicle’s hood near the stalled Jeep’s hood
- Turn off the booster vehicle
- Turn off all accessories in the stalled Jeep (Radio, heat, wipers, lights, etc.)
- Open the hoods of both vehicles
Attach the Jumper Cable Clips to the Booster Vehicle or Pack and to Your Jeep as Follows, in This Precise Order:
- Attach one red clip to the positive post of the dead battery (Look for the “+” next to the post)
- Attach the other red clip to the positive post of the booster battery
- Attach one black clip to the negative post of the booster battery (Look for the “-” next to the post)
- Attach the other black clip to the engine block or unpainted metal of the dead battery Jeep to ground the connection (Don’t put it on the negative post)
Finishing the Jump Start of Your Jeep:
Finally, allow the booster vehicle to run a few minutes and them, start the dead battery Jeep and let it run for the alternator to take over and charge the battery. Disconnect the cables in the exact reverse order. Remember to be careful throughout this process. You don’t want a shock and when the Jeep or booster vehicle is running there are moving parts you want to avoid such as the cooling fan.
It should start, if not, there may be other problems with the Jeep and you may need a tow.
What are Some of the Reasons My Jeep’s Battery Drained
Some light or switch was left on or engaged for an extended time period (Headlights or dome lights come to mind immediately)
- Loose or bad battery cables
- Corroded battery terminals or cables
- Extreme cold weather doesn’t help Jeep batteries, especially older or weaker ones
- The Jeep’s battery is just getting old
- The Jeep’s alternator isn’t doing its good as well as it used to or at all
What Can I Do to Avoid a Drained Jeep Battery?
There are steps you can take to avoid coming out to your Jeep to find it unresponsive when you go to start it. Here are a few ideas:
- Occasionally check that your Jeep’s battery connections are tight and clean. If they are not, re-tighten them or clean them with a wire brush and battery terminal cleaner
- Consider testing your Jeep’s battery with a multimeter. When the Jeep is off, the battery should read above 12 volts. When running, your Jeep’s battery terminals should give a reading of 13-14.5 volts. If it doesn’t the battery or the alternator may have problems
- If your Jeep’s battery is four or more years old, it might pay to replace at now rather than on the side of the road somewhere
- Always be sure lights and other accessories that run without the key in the ignition and in the “on” position are all turned off when leaving your Jeep for an extended period
If it isn’t My Jeep’s Battery, What Else Could Be Causing the Jeep Not to Start?
Here are some possibilities to consider if the jump start of your Jeep doesn’t work:
- The Jeep’s battery may in fact be dead—for good. The Jeep will do nothing when you go to start it
- Your alternator is dying or dead. My 1996 Jeep Cherokee (XJ) has a “GEN” light for generator, when that comes on and stays on, my alternator is on the way out
- If you hear clicking when you go to start your Jeep, it is probably the starter and not the battery at the root of your problem
- Your Jeep may have an electrical short somewhere
- Another possibility if the Jeep cranks, but doesn’t start, is your Jeep’s Crankshaft Position Sensor (CPS). If this goes bad on your Jeep, you aren’t going anywhere until it is replaced
- Finally, your Jeep’s fuel pump may not be working. The Jeep may crank, but won’t start or sputter out
Final Thoughts on Diagnosis
If your Jeep cranks, clicks, makes noise, or the headlights can be turned on, it probably isn’t your battery. The other points made above can give you a hint as to where to look for the real problem.
If you suspect your Jeep’s alternator, starter, or battery to be bad, all can be taken to your local auto parts store to be tested with more advanced machines.
Your Jeep’s CPS is a last resort, after you have eliminated the other possibilities. The replacement of a CPS is a tricky task I will cover in another article. As for your Jeep’s fuel pump or fuel pressure regulator, I will cover that in another article as well.