Why Won’t My Jeep Start, How to Diagnose and Fix in Just Minutes!

Your Jeep won’t start, and you’ve already ruled out the battery being the problem by trying to jump-start it. So what can you do now to get it running?

When a Jeep’s battery isn’t the problem, a common cause of starting issues is dirtiness or corrosion to connections. Check the battery terminals, the starter, and the ground cable to make sure they’re clean. If everything is clean and securely connected, the starter or alternator may be bad.

Here are some quick tests you can run to find out why your Jeep isn’t starting, as well as how to deal with the issue that’s causing the problem.

Clean Everything

Let’s face it: when you go offroad, your Jeep gets dirty. It might not seem like a big deal from the outside. After all, the mud splatters show you like getting out there, and they come off easy enough with a hose or a car wash. The real problem happens when you don’t look at the electrical components in the engine.

Dirt and corrosion can pose a big problem to getting your Jeep started by building up around electrical connections. The buildup weakens the connection and reduces the amount of current that can go through the channel.

To get rid of all the gunk, you’re going to want to use sandpaper. Make sure the car is completely off: no headlights or accessories on, no key in the ignition, and no one in the car who might accidentally start it. Then, take your sandpaper and scrub away the mess.

To quickly clean the battery terminals, you can use boiling water if you’re careful. Pour the boiling water over one of the terminals, and the corrosion will come right off. Just be careful to only clean one terminal at a time this way, and don’t let the water form a puddle where it touches both terminals at once. If the water links both of the terminals, it’ll short the battery.

Bad Starter

If everything is clean, then you might have a bad starter. This is an easy enough diagnosis as long as you have a friend to help and a light hammer.

If the starter is bad, then the lights and accessories will turn on, but you will only hear a clicking noise when it tries to start, with no crank trying to turn over the engine. The noise isn’t always the best indicator, though, so here’s what you need to do to see if the starter is causing the problem.

With your friend behind the wheel and trying to start the engine, use a hammer to tap lightly on the starter motor. Don’t hit it too hard: there’s no need to pound. Hitting it with the hammer can help sticking parts or misaligned gears get going and start the engine.

If this method works to get your Jeep started, then you have a problem with the starter, and the no start problem is likely to repeat itself as the starter keeps getting older. The tapping is just a temporary fix, so as soon as you get the engine humming again, start looking into replacing the starter so you don’t have to deal with that problem again.

Bad Ground Connection

If the tap test didn’t work, then it may be the ground cable that’s causing the problem rather than the starter. If the ground cable can’t handle enough current, then it doesn’t matter whether the starter works or not because the engine won’t accept the power. So, it’ll only let as much electric current out of the battery as the ground cable can handle.

So if the ground cable can let a little energy through but not a lot, you’ll hear the starter clicking, but you won’t hear any attempt to turn the engine. That’s because the starter requires only a little power to click its solenoid, but it takes a lot more power to crank the engine.

But that’s the same noise as it had when the starter was bad, so how can we diagnose this problem? The answer is with a conductivity test. For that, you’ll need a multimeter set to ohms. This test is going to show you how strong the connection is between the negative terminal of the battery and the ground metal of the car.

With your multimeter set to ohms, touch one probe to the negative terminal, and touch the other to any metal part of the engine. The reading should be zero or close to zero ohms. Then, conduct the same test between the negative terminal of the battery and any metal part of the body of the car that isn’t painted.

If this test fails, then you’ll need to fix the connection between the ground cable and the engine. This could mean either cleaning off the ground cable and/or its connections to the engine or tightening up the connection.

Alternator Problems

But maybe your problem is entirely different: maybe the engine starts but dies after only a few minutes. Maybe you managed to jump-start it only to have it die again shortly afterward. Or maybe it doesn’t do anything at all when you turn the key. If any of these seem like your situation, then you may have an alternator problem.

If you think the alternator may be the culprit, think back to your recent experiences in the car. How were the accessories doing while the car was running? Could you have both the air conditioning and the radio on full blast at the same time, or did having one on decrease the output of the other? Were the headlights as bright or dimmer as they should be?

These accessories all get their power from the battery, which is charged by the alternator while the car is running. So if the alternator stops working, it’ll stop charging the battery, so you’re likely to see a decline in the accessories, which will foretell the battery running out and being unable to feed the engine’s electrical needs.

You’ll know you have an alternator problem when you see these signs and know that the battery is healthy. The alternator will need either a repair or replacement.