Why a Car Won’t Start in the Rain?


No one wants car troubles on a rainy day but that is when some cars seem to give their owners a lot of trouble. The problems can range from the battery to the distributor depending on the car make and model.

Spark plugs are the number one issue why car won’t start in the rain. Other issues can arise from moisture getting into the distributor cap, affecting the corrosion on the battery, water getting into the fuel filter, a short in the electrical system, belts, or a sensor. 

Read on to find out how to identify the exact problem your vehicle is having in the rain.

Spark Plug Issues

The insulation around the spark plug wires can wear down and the moisture causes the voltage to go to the car engine metal rather than the spark plug. You can see this if you open the hood and have someone crank the car. 

What you will see, if this is the problem, is the arc of voltage going toward other metal pieces in the car instead of the spark plugs. It is a common problem that will cause the car to misfire, according to mechanics.

Spark plugs are necessary to generate the voltage to start the car. Bad spark plugs or old wiring will show more problems in the rain but can cause issues anytime.

This is a simple fix simply by having the spark plugs and wires replaced. They should be replaced on a routine schedule so check for your make and model to see how often they should be rotated out.

Read: Why Is There Oil On My Spark Plug Threads?

Distributor Cap Issues

A distributor cap develops cracks over time and that can allow moisture to creep in. Look to see if there are any cracks. It’s also a good idea to remove it to see if the inside is wet. Wipe it down, replace and try to crank the car again. 

A car won’t start with a wet distributor cap. The distributor cap is an important piece when it comes to cranking the car as protects the distributor and holds the contacts between the spark plug wires and the internal rotor.

Water getting into the distributor or those contacts will cause both short and long-term vehicle issues.

Read: Bad Camshaft Position Sensor Symptoms

Battery Issues

Older batteries are particularly troublesome in the rain as they already are losing the capacity to give power to the starter. A bigger issue is corrosion on the terminals. There tends to be more of it accumulating during rain so you may want to check if it’s been raining a good bit. 

Fixing corrosion on a battery is something people can do themselves. 

First, look at the battery terminals and see if there is a flakey white or green substance on them. That’s corrosion. 

Disconnect the battery. Take an old toothbrush and dip it into a paste of baking soda and water. Scrub all over the terminals and the battery connectors and wipe with a clean cloth. 

Reconnect the battery and try to crank the car again.

Read: How Long Can a Car Battery Sit Unused?

Fuel Filter Problems

One of the problems with rain and minor flooding is that it splashes water everywhere. Cars that don’t have good seals around the windows, hoods, and throughout can accumulate water in places where they shouldn’t. 

That means water can get into the fuel filter or even into your gas tank and that can cause some big engine problems. 

Check the seals around your car and engine to make sure they are okay. Fill up with a good gas to see if that solves the problem. It could be that you are running on a low tank, causing water to outmeasure the gas and that can have a significant impact if it gets into the system. 

You may want to add an engine additive when you fill up to boost the power of your gas. 

This is a short-term fix. If water is getting into your fuel filter or your tank, you will need a permanent solution. That involves taking your vehicle to a mechanic to see how water is getting into the fuel filter or tank and then having them fix it. 

Constant water into these areas will call major engine problems over time so it would be cheaper to fix it now rather than try to hold off to avoid a mechanic’s bill.

Read: How Often Should The Fuel Filter Be Changed?

Electrical Problems

Mechanics say one of the most common problems is that water gets into the car and short circuits some electrical wiring.  This goes back to proper seals but could also occur because of older wires that need to be replaced. 

Some car owners said the most affected wiring during the rain was ignition and turn signals. Their vehicle worked fine once they replaced those wires. 

This type of problem points to problems with seals around the windshield or doors. Water can come through those areas to affect wires around the steering column. You will need to specifically check those seals if you find problems with ignition or turn signal wires because fixing the wiring won’t resolve the overall problem.


Belt Issues

Mechanics also said water can affect belts if it gets to them as well as electrical. Ongoing moisture can cause belts to slip and that can affect power steering as well as cranking the car. 

This can be a dangerous situation if the steering goes out while you are on the road.

You should check your belts regularly, make sure they remain in good order with no stretching or cracks. A good belt shouldn’t be affected by the rain.

Read: What Happens To A Car When The Serpentine Belt Breaks?

Sensor Problems

Finally, rain could be affecting a sensor and that can cause problems elsewhere in the car. Modern cars have an enormous number of sensors and any one of them can cause a variety of problems if they get wet. 

It will take a professional diagnostic service to determine if you have a sensor issue. You should look at sensors if all the other common rain issues are checked and determined to not be the source of the problem. 

Sensors can be replaced by a mechanic. Unfortunately, they are some of the more expensive items to fix as they work with the computer aspects of the vehicle. 


What happens if the engine is rained on?

Enginnes that get really wet will choke. That is unlikely to happen unless you are in floodwaters. Normal humidity and water can’t seep through a metal engine. 

Can heavy rain make a battery go dead?

Rain doesn’t affect the internal elements of a battery but batteries may seem like they lag on rainy days. That could be because increased humidity can contribute to corrosion on the terminals. That can prevent a battery from performing optimally. 

Read: Does a Car Battery Drain Faster In Cold?

Does rain affect car performance?

Rain can affect how your car handles and responds. It depends on the make, model, and the tires it has. Some high-performance cars handle well in the rain while others should be handled with care. Generally, drivers should take extra time and car while driving in the rain because of less visability and slick roads.

Why does my car stall in the rain?

Stalling in the rain is a spark plug issue. Rain gets into the cylinder of the spark plug and causes it to fail, so the engine stalls. Make sure there are no cracks on the cylinders and get your spark plugs changed on a regular basis.

Can you leave your car hood open in the rain?

This isn’t a good practice but typically doesn’t do any harm to your engine if it happens occasionally. It’s best not to allow rain or snow on what’s under the hood. Another problem could be heavy wind messing up your open hood.

Leave a Comment