Forgetting to top up the fuel tank to the brim is among the main causes of a Jeep that won’t start — and it can happen even to the best of us. But that’s just one of the many factors that lead to this dilemma. Beyond a starved engine, there are other more pressing culprits behind this scenario that you should be aware of — and that this article will shed light on.
Usually, a Jeep won’t start when requisites for air, fuel, and spark are not met. There are several reasons behind this — plugged filters and injectors, a compromised fuel pump, and a defective battery or alternator. In some cases, however, the problem is due to driver or upkeep neglect.
Here are 12 reasons why a Jeep won’t start:
- Fuel Tank Low or Empty
- Depleted or Corroded Battery
- Faulty Starter Motor or Electrical Circuit
- Malfunctioning Alternator
- Lack of Spark
- Blown Fuses
- Steering Wheel Lock
- Restricted Fuel Filters/Injectors
- Impaired Fuel Pump
- Disrupted Timing Belt
- Jammed Purge Control Valve
- Engine Failure
It’s important to note that these aggressors aren’t exclusive to Jeep models. Like any other motorized vehicle, Jeeps need to get their ignition, fuel delivery, and compression settings up to spec to operate efficiently and correctly. At any point that one of these parameters fails, the flaw is then carried over to other vehicular systems, causing a ripple effect.
Stay with me through this guide and learn more about these causes to address them more effectively.
Reasons Your Jeep Won’t Start
1. Fuel Tank Low or Empty
As with all motorized vehicles, a low or empty fuel tank can cause a Jeep not to start due to low fuel for engine ignition. While your Jeep’s battery might have enough charge to power lights and accessories, it won’t have sufficient gas for the engine and ignition system to start.
To resolve this issue, the most straightforward solution is to refuel your Jeep at the nearest pump station. In cases where this isn’t immediately possible, you can use a classic gas can with even a small amount of fuel to attempt a startup and confirm if low fuel is the root cause.
Note, however, that a shortage of fuel reaching the engine could result from other factors, such as a clogged fuel filter or obstructed fuel lines. That said, proceed with a systematic examination of your Jeep’s fuel system — especially if your gas tank is full.
Confirm that the fuel lines are unhindered and the fuel filter is clean. Attempt to start the engine by introducing starting fluid into the intake. If the engine briefly starts but then stalls, it strongly suggests insufficient fuel delivery to the engine, prompting further investigation into the fuel pump’s functionality.
2. Depleted or Corroded Battery
If your Jeep refuses to start immediately after driving, it could result from a fully drained or worn-out battery, potentially with loose or corroded terminals. This scenario is common with used vehicles, where the battery’s lifespan might be overlooked until issues arise. Extended use of headlights or fully depleting the battery are examples of ‘bad habits’ that can lead to a voltage drop, preventing the engine from cranking and the alternator from recharging it.
Batteries typically last 3—6 years, making it vital to investigate if your battery is causing the startup problem after a weekend adventure. You can rule out the battery by jump-starting your trusty four-wheeler and checking the alternator’s output, which should read above 12V.
This diagnostic step helps differentiate between a dead battery and a faulty alternator, avoiding unnecessary battery replacements and ensuring the battery’s posts are free of obstruction. You may also revert to one of my older posts concerning other battery symptoms potentially indicative of discharge or corrosion.
3. Faulty Starter Motor or Electrical Circuit
Often disguised as a weak battery symptom, a defective starter relay is another prevalent culprit to why a Jeep won’t start. It could be due to a shot relay/solenoid or faulty ignition switch and may be accompanied by ‘ignition clicks’ — just like with alternator issues.
This series of clicks is good news, as it signifies that the starter motor is actuating but not engaging with the flywheel. When you encounter this symptom, you’d know to inspect if any tooth on your starter drive gear or engine flywheel (view on Amazon) is missing or chipped. Of course, confirming this wouldn’t exempt you from replacing your starter relay or motor altogether.
4. Malfunctioning Alternator
Alternator failure is another potential cause of no-start issues in Jeeps — “Jeep Cherokee won’t start,” in particular. The alternator in these vehicles may only be shorted in some instances. However, 2012—2014 models can have a defective alternator that could catch fire while driving, according to Moto Verso.
Alternator failure can result in a loss of electrical power. This, in turn, could render vital systems like the central body controller, electronic stability control system, anti-lock braking system (ABS), cornering brake control (CBC), and electronic control module non-operable.
While it makes sense for a depleted battery to be associated with a defective alternator (as established in item #2 above), this conclusion doesn’t always turn out to be the case. If the alternator is acting up and the battery remains discharged, it’s best to include a worn or slipping accessory drive in your list of suspects. Additionally, keep an eye out for a slow cranking starter, dimming headlights, or whether your Jeep won’t start and just clicks — these signal a bad alternator (if not poor or weak alternator output).
Depending on your Jeep’s year and model, it may not even have an alternator gauge in its instrument panel. You may want to test the alternator using a proper gauge like Foxwell BT780 6V/12V/24V Car Battery Tester (view on Amazon) to see if the output is up to spec.
5. Lack of Spark
The absence or lack of spark can be attributed to several factors. However, three stand out — defective plug, improperly timed spark, and engine flooding. A faulty spark plug is the most common of the lot and entails replacing the erring spark plug. Meanwhile, the other two require correcting the Jeep’s timing system and drying out the ‘drenched’ spark plugs before testing them (provided they’re not in bad shape).
Relative to this, I highly recommend having an adjustable spark tester (view on Amazon) as part of the staples in your tool kit to scrutinize the proper arc of plugs and ignition coils. Procure one that can test for 40KV, 30KV, and 10KV spark. A thorough visual inspection of the distributor cap and a close examination of the cylinders’ firing timing are necessary.
6. Blown Fuses
Despite Jeep’s renowned ruggedness, its electrical systems are not impervious to deterioration, overloading, or damage, leading to blown fuses. To add, identifying a blown fuse (a common reason for Jeeps not starting despite having power) can be difficult due to the numerous fuses scattered throughout the vehicle’s electrical system.
Checking a fuse involves safely removing it from its fuse holder, ensuring the vehicle is completely turned off, and the ignition key is removed. Once it’s detached, you need to examine it for visible signs of a gap in the wire or a dark or metallic smear inside the fuse’s glass.
But don’t be fooled — this seemingly straightforward process isn’t as easy as it seems. Replacing a fuse on a Jeep isn’t recommended for DIY repairs. Attempting to replace a fuse yourself is doable but may risk the integrity of your vehicle’s electrical system. Many Jeepsters strongly suggest having a qualified mechanic inspect the suspected blown fuse and address the issue.
7. Steering Wheel Lock
Not to be confused with the anti-theft feature in most modern 4x4s, wheel lock typically happens after turning the steering wheel fully in one direction (making a sharp turn or attempting to drift, perhaps?). It’s pretty much the same safety mechanism at work behind the scenes. But instead of ignition key removal causing the steering wheel (view on Amazon) to be pushed back against the locking pawl, aggressive steering maneuvers do the trick.
At times, it’s also tied to starting a Jeep without making sure that the gear is fully engaged in Park, resulting in a “Jeep won’t start in Park” scenario.
Interestingly, service manuals of most newer Jeeps don’t contain instructions on bypassing a steering wheel lock caused by aggressive steering maneuvers. They do have instructions for the ‘passive’ wheel lock (the feature triggered by the absence of the key in the ignition). The general rule is to turn the steering wheel slightly in the same direction that engaged the lock (whether inadvertently or otherwise) to release the pressure off the ignition lock.
8. Restricted Fuel Filters/Injectors
There is no singularly exclusive symptom tied to this culprit. But if we were to think of one, the closest would have to be stalling at startup (followed by the engine of your Jeep dying shortly after). The scenario I just described is very telling of fuel not getting to your vehicle’s cylinders and is a prevalent cause of no-start issues — including 2021 Jeep Wranglers that won’t start.
Obstruction in the fuel filters or injectors is often due to debris buildup in the fuel tank (which eventually becomes engine sludge) — although this isn’t the only trigger behind fuel pressure buildup. Running your Jeep dry is another factor that exacerbates the clogging of fuel filters. You may also want to pay mind to how the engine responds when the ignition is turned on, as this may signal a need to scrutinize other fuel delivery system components.
Thankfully, fuel-injected Jeep Wranglers make it a tad easier to test fuel lines for obstructions via the Schrader valve. All you need is a screwdriver to press it (provided you’ve turned the power mill on and adequately primed the line with fuel). The expectation is that fuel should squirt out of this valve. Otherwise, inspection of the fuel pump or fuel pressure regulator is advised.
9. Impaired Fuel Pump
As early as discussing the role of a low-depleted fuel tank in causing no-start issues, I’ve mentioned the need to thoroughly inspect the condition of your Jeep’s fuel pump. There’s good reason for underscoring this component — it is, after all, responsible for maintaining consistent and appropriate fuel pressure crucial for your beloved four-wheeler to fire up.
The health of a fuel pump is especially significant in the operation of EFI-equipped Jeep models. Consistent fuel pressure keeps fuel moving through critical fuel system components until it reaches the combustion chamber, where it’s converted to energy that makes your four-wheeler mobile.
Because of how it functions, a fuel pump (view on Amazon) essentially has more mileage than the wheels or the actual vehicle. This also means it’s twice as prone to failure and deterioration than the components mentioned.
10. Disrupted Timing Belt
If my memory serves me right, I did mention in an old post that inspecting the timing belt or chain for oddities is fairly straightforward. I’ve since changed my opinion on the matter. And if you’ve done your research, how easy or difficult the process is depends on who you ask. Forum frequenters are also conflicted with their take on this, which is quite understandable given the varying responses and expertise they’ve encountered in these online forums.
My sentiment, however, doesn’t change the fact that inspecting the timing belt or chain would be inevitable at some point when dealing with no-start issues. Especially if your Jeep is primarily used for off-roading more than as a daily driver, expect the rotation between your camshaft and crankshaft to eventually become out-of-sync. Outside of off-road abuse, regular urban driving could lead to normal wear and tear, excessive oil saturation, or both.
11. Jammed Purge Control Valve
In my post on Car Won’t Start After Getting Gas, I’ve extensively explained how a purge control valve that’s stuck open contributes to no-starts and how to best fix it. That explanation still holds even for Jeep Wranglers and other models. This EVAP system component helps reduce engine temperature and harmful emissions. When those two facets are upset, engine flooding and unburnt fuel vapors are bound to happen, resulting in a Jeep that won’t start.
12. Engine Failure
Finally, we have the worst-case scenario of what would trigger your Jeep’s no-start issue — engine failure. All the critical components that help fire up your 4×4 are no longer working as they should. And while there is a slew of factors that we can blame for this occurrence, it’s usually driver negligence and neglect of proper upkeep that sets this problem in motion.
Any of the preceding items, when left unattended, could escalate to this predicament (perhaps, except those related to your Jeep’s electrical systems). Addressing this culprit isn’t going to be a walk in the park. Nor is it going to be economical.
Conclusion — Jeep Won’t Start: 12 Reasons & How to Fix
Remember not to repeatedly crank your engine and force it to fire up. Instead, Perform a diagnostic scan or follow the other tips mentioned in this guide to pinpoint the fault. If those general guidelines don’t help and you’ve exhausted all possible troubleshooting methods, it’s time to outsource resolving your no-start issue to your local mechanic or a qualified professional.
Kris is an avid off-roader and outdoor enthusiast who loves to brave the elements and take on challenging terrain. He also enjoys sharing his passion and knowledge with others so that they, too, can appreciate the ride.