Key Takeaways

  • Slow starting, 90% of the time is due to a starter motor cable or fuel pump issue.
  • Perform a voltage drop test to determine if your starter cable is bad.
  • Changing your fuel filter may increase your vehicle’s starting capacity.
  • Fuel injectors can be cleaned with fuel additives.
  • Replacing the starter will most likely not fix the issue.

This post may include affiliate links. If you make a purchase through these links, we'll receive a commission at no extra cost to you. This support helps us maintain and grow our site. Thank you for your support!

When your car struggles to start it can be a worrisome event. If you discover that it’s not the battery you might start to wonder why it’s struggling.

Check the following items if your car struggles to start but the battery is fine:

  • Fuel pump
  • Fuel filters
  • Fuel injectors
  • Starter

I’m a mechanic with five years experience diagnosing and repairing vehicles. I am ASE certified and received my degree in automotive repair. I receive regular training on the latest released automotive technology. And I repair and diagnose vehicles with the latest and most up to date tools and software.

Table of Contents

Car Struggles To Start But Battery Is Fine

When your car struggles to start it can be worrisome. Without a vehicle that starts, you have no vehicle.

So when your car starts to struggle after you hit the ignition switch, you should fix the issue immediately. But how so? Let’s look at some of the reasons why your car would struggle to start and some potential solutions.


The first reason that your car would struggle to start is that you have a bad starter. Starters are their own electric motors. When starters have an issue it can cause the motor to operate sluggishly.

One reason the starter motor can operate sluggishly is because the cable running from the battery to the starter has become loose or corroded.

A loose starter cable will cause a slow start issue because not enough voltage is getting through to the starter. Therefore, in this case, the starter will not be operating at full capacity.

If you check the starter cables and battery terminals for tightness and corrosion and everything checks out, there are some more tests you can do.

To check the starter cable, perform a voltage drop test on the starter motor cable. To perform this test you’ll need a digital voltmeter.

Next you’ll want to disable the fuel system by pulling out the fuel pump relay. Or you can remove all of the spark plugs.

You want to disable the fuel or ignition system because you want to crank the engine for 5-10 seconds without actually starting the engine.

Next, take the red lead of the voltmeter and hook it up to the positive terminal of the battery. And take the black lead and hook it up to the “B” terminal of the solenoid.

Now you have your leads hooked up, it's time to start the starter. Start the starter and take note of the reading on the digital voltmeter.

If your voltmeter reads more than half a volt (0.5v), then your cable needs to be replaced. This is good news since you don’t have to replace the starter. You just have to replace a cable or tighten one down.

A half volt of energy being stored in the cable means that there’s too much energy clogged up in the cable and it needs to be replaced.

If you have slow or sluggish starting, start your diagnostic process with the starter, starter cable, and a voltage drop test.

Fuel Pump

If your starter, starter cable, and battery all check out, the next place you should navigate your diagnostic journey to is the fuel pump. A fuel pump is a device that is stored in your vehicle’s gas tank.

The fuel pump is an electric motor that sucks up fuel in the gas tank, pressurizes it, and sends it to the fuel injectors.

The fuel delivered by the fuel pump to the combustion chamber is then ignited by the spark plug causing a small explosion inside the chamber. This combustion is what drives the piston down, turning the crankshaft, and causing the engine to run.

When your fuel pump starts to fail, it stops delivering fuel to the injectors. But fuel pumps don’t stop working all at once. They can stop working gradually over time. They can also start to lose their effectiveness. This means that they can operate at 50% capacity.

If your vehicle is struggling to start, your fuel pump may be attempting to deliver fuel to the injectors but may just be doing a horrible job at it. So when you go to start your car, the car battery will be working fine, but the engine will be starved of fuel. This will cause a slow start issue.

With a failing fuel pump you may be able to start your car after it struggles to start. Once fuel is pressurized in the fuel lines, fuel has an easier time getting to the injectors. But on a cold start fuel has a harder time getting to the engine with a faulty fuel pump.

To test whether or not your car has a bad fuel pump, get some brake clean and spray it in the intake manifold while your car is struggling to start.

If your vehicle starts up right away after you spray the brake clean (technically fuel) into the intake manifold, this is a sign your fuel pump is failing to deliver the fuel your engine needs to operate.

Fuel Filter

The fuel filter's job is to filter out any contaminants that can get into your fuel tank. It's like an engine oil filter. The fuel filter wants to take any particles out of the fuel that don’t belong there.

Contaminants that get into a fuel line or the combustion chamber can cause issues for your engine. So car manufacturers filter out these particles by placing a filter inside the fuel system.

But after time, fuel filters can lead to low fuel pressure. While the vehicle’s electrical system will be operating totally fine, the fuel filter could be clogged causing fuel in the fuel line to be backed up.

This loss of fuel pressure to the injectors can cause a slow start issue. A slow start issue when the fuel filter is clogged is your engine's way of gasping for air. But instead of gasping for air, it’s gasping for fuel.

Without fuel, combustion cannot happen inside the engine’s cylinders. And a fuel clog in the fuel filter will cause minimal fuel to come through the fuel lines. To fix this, the remedy is pretty simple.

All you have to do is change the fuel filter. Changing the fuel filter is relatively simple. Fuel filters are directly in the fuel line and held in with clips. A fuel filter just needs to simply be removed and replaced. Do not have electrical power going to the fuel pump while you are changing the fuel filter.

Pressurizing a fuel line while changing the fuel filter can result in disaster. So make sure to shut off the car while removing the fuel filter.

Fuel Injectors

Fuel injectors are the part of the vehicle that’s responsible for injecting fuel into the combustion chamber. These little devices squirt little teaspoon amounts of fuel into a combustion chamber with each revolution of a crankshaft.

The fuel injectors are always under pressure and work by opening up a valve electronically.

When the valve on the injector opens up, pressure from the fuel rail forces fuel out of the injector and into the combustion chamber.

But these fuel injectors can become clogged. Fuel injectors can become clogged because carbon deposits build up on the valves. The carbon deposits come from the combustion of gasoline.

When carbon deposits build up on fuel injectors, fuel has a hard time coming out of the fuel injector.

This will cause the amount of fuel that’s injected to not be enough needed to start the engine.

For example, let's say you needed a teaspoon worth of fuel in each cylinder to start the engine. When the injector is clogged, only a half teaspoon will come out of the injectors.

This causes the combustion process to become incomplete and will cause a car to struggle to start. There are many different ways to fix the issue of faulty or clogged fuel injectors.

The first way is to clean the injectors with a fuel additive. A fuel additive works by adding liquid to your fuel tank.

And when the liquid runs through the injectors, the liquid cleans the injectors as the cleaner is pushed through the fuel system. This liquid cleaner or fuel additive removes carbon deposits and unclogged the fuel injectors.

Another method is to just replace the fuel injectors. Replacing the fuel injectors is quite easy and inexpensive.

Just remove the old injectors and replace them with new ones. Sometimes intricate clips are involved but the process is pretty self explanatory.

Car Struggles To Start But Battery Is Fine (Potential Solutions)

About The Author

Christopher Sparks

Christopher Sparks

Christopher Sparks has been servicing vehicles since 2012. After completing the automotive studies program at Camden County College, he was awarded an Associates's Degree in Applied Science. His first job was a lube-tech at Jiffy Lube, and is currently an independent B-Technician servicing vehicles for the United States Postal Service. Christopher is ASE certified and loves rebuilding engines.

Read more about Christopher Sparks