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Temperamental Car: Reasons and Fixes for Hot-Start Failure

ByMatsumoto Naoki-February 16, 2021

A long drive in hot weather can mess up the engine of a car. When you try to start the car after a short break, the starter responds but the engine does not catch up. Such a condition is known as a temperamental car and this particularly happens with some old Honda models. What does cause this hot-start failure and how to solve this issue?

The Reasons for a Temperamental Car

Hot weather and long drive are definitely responsible for a car to act up this way but these are not the only reasons. In fact, any car in perfectly good health can drive hour after hour under the scorching sun without facing this issue. The main culprit here is the fuel pump relay.

You will find the relay by looking under the dashboard at the driver’s side floorboard. In older Honda models, this relay stops working when it gets overheated. Although Honda has fixed this problem decades ago, many vintage models are still running.

Keeping the windows down could help. (Credit: PxHere)

The owners of such a model are quite aware of this problem. It only happens because the fuel pump relay stops working when hot weather turns the car into an oven.

The relay closes when you start the vehicle. By doing so, it sends power to the fuel pump, so it can send fuel to the engine through the fuel injectors. However, an overheated relay does not close, which means no fuel goes into the engine. As a result, the car does not start.

How to Solve the Hot-Start Failure Issue?

As the problem occurs due to the fuel pump relay getting overheated, your car will run again if you can get the relay back to the normal state. So, if you are driving an old Honda and it’s hot like hell out there, be careful that the interior does not turn into an oven.

There are two kinds of fixes for this problem — temporary and permanent solutions.

Temporary Fixes

If the car does not start on a hot day, waiting for 20 to 30 minutes may work. Don’t forget to keep the doors open or rolling down the windows. It will cool down the relay, which will start functioning again.

Some people think that hosing down the hood will solve this hot-start failure issue. Well, it does nothing except for wasting plenty of water. The main key is cooling down the passenger compartment.

Your car will start after keeping the doors and windows open for a while. However, it will possibly be a rough start and you need to add plenty of fuel to the gas tank and rev the engine a little for the car to run smoothly.

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Permanent Fixes

The best way to solve this annoying problem is to replace the fuel pump relay. It’s a really cheap fix as a new relay costs around $50. Once replaced, it will last for approximately 10 years. So, it’s better to get rid of the temperamental car problem in this way and enjoy a day trip on a summer day without facing any hot-start failure.

Matsumoto Naoki is senior car blogger at Car From Japan. Having background in mechanical engineering, he has a unique perspective on a lot of new car innovations. Prior to Car From Japan, Matsumoto was Mechanical Design Engineer at Yajima Plant, Subaru Corporation. His articles provide detailed DIY instructions and how-tos to help you get your new car on the road. If you want to save money and feel more confident when working on your cars, you should not ignore Matsumoto’s sharing posts. He presents driving tips and tricks for everyone through easy-following steps and mechanically but friendly writing.

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