What Is an Inertia Switch? How It Works, Signs of Failure, and More

The inertia switch or fuel pump shut-off switch  on Ford vehicles is a device designed to cut the power to the electric fuel pump in fuel injection systems in the event of a crash.

Any sudden impact that causes rapid deceleration causes the switch to open and puts the fuel injection system into fuel shutoff mode. An activated inertia switch keeps fuel from being pumped into the system to minimize the risk of fire in case the system has developed a leak.

Once it is triggered, it must be reset manually by pushing a button on top of the device which restores current to the fuel pump. This button usually comes in a red or yellow color.

It is typically located in the rear of the vehicle between the electric fuel pump and its power supply. It can be found on the passenger side in some vehicles, right behind the glove compartment.

There should be a picture or wording that indicates the inertia switch is behind the plastic panel.

Signs of a Bad Inertia Switch

Much like other car components, the inertia switch may malfunction. A sign to look out for is a no-start condition.

No-Start Condition

A tripped inertia switch may cause the engine to turn over but not fire up or keep it from turning over at all.

Both scenarios are caused by a disabled fuel pump. However, keep in mind that issues in other vehicle systems may cause a no-start condition, so it’s best to get your vehicle properly diagnosed by a mechanic before jumping to conclusions.

How to Reset the Inertia Switch

Resetting the inertia switch could fix some of the issues previously mentioned, especially when it is tripped in error. Here’s how to do it:

Locate the Inertia Switch

Before resetting the switch, you’ll first have to find its location. Your owner’s manual will often indicate its location and how to properly access it.

It’s typically located behind the glove compartment on the passenger side. The switch will look like a small box with a black, red, or yellow cap with an electrical connector at the bottom. The switch could also be in the trunk at the rear of the vehicle or under a side floor pan by the passenger seat.

Prepare the Vehicle

Preparing your vehicle is crucial to avoid damaging your fuel pump. To ensure safety, follow the steps below:

• Step 1: Turn off the ignition and remove the keys from the ignition lock cylinder.
• Step 2: Check underneath the hood for any potential leaks.
• Step 3: Walk around the vehicle and look for other possible leaks that may come from the fuel lines or fuel tank.

Press the Inertia Switch

Press the inertia switch to reset. Some designs may require you to pull a lever instead.

Turn the ignition on for at least ten seconds and then turn it off to pressurize the fuel system. Start and idle the engine for at least a minute to ensure that fuel is properly flowing to the injectors.

Check for leaks before turning the ignition off. Put the plastic cover back on the switch and reinstall any panel that you had to remove to get access to the device.

How Long Do Inertia Switches Last?

The inertia switch is designed to last as long as the vehicle’s lifespan. However, different circumstances such as rough driving conditions as well as wear and tear may cause it to malfunction and require replacement.

Where to Get a Replacement Inertia Switch for Your Vehicle

As mentioned previously, failing to repair or replace a faulty inertia switch can cause problems, like stalling and no-start conditions. So don’t put off replacing yours if it’s malfunctioning. Luckily, finding a high-quality yet affordable replacement is easy at CarParts.com.

We source our car components are sourced from the most reliable names in the industry to ensure they work like your stock part. Despite that, our inertia switches come with a low-price guarantee, so you can fix your ride without going over budget.

The best part? Ordering a new switch is simpler than ever thanks to our vehicle selector and filters. Enter your ride’s details into the tool to view compatible parts, then change the filters to narrow down the selection to your preferred brand, price, and features.

Order a replacement inertia switch now, and we’ll deliver your product straight to your doorstep in as fast as two business days. Check out our catalog and shop now.