3 Simple DIY Methods How To Check For Leaking Fuel Injectors

Just like the fuel pressure sensor, fuel injectors are a key part of a complex fuel management system. If you have a leaking fuel injector, it could cause severe damage to your engine.

In this article, we’ll show you how to check for leaking fuel injectors.

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We’re going to walk you through everything step by step on how to inspect and diagnose a leaking fuel injector.

In general, a car has one fuel injector per cylinder. To find out which injector is leaking, you need to check them one by one.

Symptoms of leaking fuel injectors

In 2021, there is concern that the Atlas SUV has an issue with leaking fuel injectors.

Owners say they can smell gasoline, see gas leaking from the engine compartment, and often have check engine warning lights come on that indicate a problem.

Symptoms like either poor acceleration, an engine misfire, or engine stalling while driving are a sign that you may have a leaking fuel injector.

The worst thing that could happen is oil thinning and engine knock, both are catastrophic to your engine.

Moreover, internal injector leaks can cause an overly rich mixture, whereas an external injector leak is a fire hazard. So you need to find out which injector is leaking.

P029D Cylinder 1 Injector Leaking

This is a general powertrain trouble code that applies to OBD-II vehicles. Generic repair steps will also vary depending on when your car was manufactured and what kind of engine it came with.

If your OBD-II equipped vehicle has stored code P029D, you may have a fuel injector leak for cylinder #1.

How to check for leaking fuel injectors

The best way to check for leaking fuel injectors is to inspect the O-rings and the fuel injector body. These are the most common locations that they begin to leak.

Inspect the connection point between each fuel injector and the fuel rail. Look for any signs of a leak or gas smell on the rail, injector body, or cylinder head.

If you observed any leaks, it means that you have bad O-ring seals inside the injector body.

Method 1. Inspect the fuel injector and fuel rail connection

The first leaking fuel injector test is through visual inspection.

Step 1. Put the car in park or neutral and apply the emergency brakes

Before you start looking for leaks, you must first remove the negative battery cable on your car.

Step 2. Visually inspect each fuel injector in the fuel rail

If you observe any fuel spray pattern or gas smell at the injector head it means you have bad O-ring seals that need to be replaced.

Method 2. Residual pressure test

This is another method how to check for leaking fuel injectors.

Step 1. Find the service valve port and depressurize the system

Using a socket, slowly open the cap, while holding a rag over it, until you hear the hiss of the pressure. If your service valve port has a pressure release pin, push the pin using a screwdriver

Step 2. Fit a fuel pressure gauge to the pressure test fitting

Screw the fuel pressure gauge onto the fitting. You may also use the push-on adapter.

Step 3. Cycle the ignition key from “OFF” to “ON” position several times.

DO NOT START THE CAR. Just turn it to the “ON” position. Then turn it off. This will re-pressurize the system.

Step 4. Look at the reading on the gauge

In general, the reading will be anywhere 30 to 80 psi depending on your car. Check if the pressure remains constant after several minutes.

If the pressure drops quickly, there may be a leaking fuel injector. However, this could also mean a bad fuel pressure regulator or a bad check valve on the fuel pump.

Here’s a video demonstration from ChrisFix.

Method 3. Fuel pressure leak-down test

This method requires knowledge on removing the fuel injector together with the fuel rail. Knowledge of grounding fuel pump terminals is also required.

Prepare four (depending on how many injectors you have) empty plastic bottles. These will serve as “buckets” to catch the fuel leaking from the injectors if there are any.

Step 1. Depressurize the fuel rail, if you have pressurized it for the residual pressure test

Make sure that you have depressurized the fuel rail again.

Step 2. Remove the fuel injector together with the distribution pipe.

WARNING: Make sure you secure the injectors to the rail or they WILL blow off and spray fuel everywhere! 

Step 3. Place each injector tip inside the plastic bottle

In case the fuel injectors leak they will spill inside the plastic bottle. And you can pour off the fuel.

Step 4. Using jumper wires, ground the fuel pump terminal

Just place pins on the alligator clip to the fuel pump terminal and attach the other side of the alligator clip to body ground.

Step 5. Turn the key from “OFF” to “ON”

Step 6. Tilt the injectors approx. 60 degrees to check for leaks

If you have installed a fuel pressure gauge, check if it remains constant for a few minutes. 

One drop per 2 minutes pressurization is acceptable. If you do find any leaks, replace the damaged injector.

Related: If One Fuel Injector Is Bad Should I Replace Them All?

Other parts which may also cause fuel injector leaks are the O-rings, sealing, and check valve in the pump.

If you don’t find any leaks in the fuel injector, but the pressure drops significantly, then it could be any of the following: a bad fuel pressure regulator, a leak in the fuel line, or a bad fuel pump.

Step 7. Turn the ignition switch “OFF” and remove the jumper wires


A leaking fuel injector can cause severe engine damage and poor performance. But you don’t need to panic, there are several ways to detect a leak before it’s too late.

This article discussed the 3 DIY methods how to check for leaking fuel injectors. The best way is by inspecting the O-rings and the fuel injector body- these are the most common locations where they begin to leak.

You could also try one of 3 DIY methods:

First, look for leaks at your connection between the fuel rail and injectors, then perform a residual pressure test and finally do a fuel pressure leak-down test if you suspect an internal leakage in either case.

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