Tips from a Ford Diesel Mechanic: What Is an ICP?

silver pickup truck isolated

Whether you’re a die-hard diesel enthusiast who pulls everything from horse trailers to construction equipment or you’re just interested in diesel technology, you’ve likely come across the term “ICP” more than a few times while researching diesel trucks. Continue reading

How to Test and Clean Fuel Injectors

mechanic fixing fuel injector

We all want the best mileage and performance from our vehicles, and one of the keys to an optimally functioning engine is a clean fuel injector. However, additives and hydrocarbons present in fuel can often leave gunk or buildup around the nozzle of the injector, causing poor fuel flow, ineffective atomization, and uneven distribution.

Ideally, you should be fueling your vehicle with a high-quality fuel that limits the amount of buildup in your injectors. However, even the most well-fueled injectors must be cleaned or replaced at some point.

Unlike many engine parts which require regular maintenance, there is no specific time or mileage that indicates when you need to clean your injectors. Fortunately, when your fuel injector is dirty, your vehicle has many ways to let you know that it is time to clean them.

Symptoms of a Dirty Fuel Injector

One of the first things you will notice is a significant reduction in power or acceleration. Reduced power is often due to an ineffective ratio of air to fuel, which can result from a clogged nozzle.

You may also notice a decrease in fuel efficiency as your engine uses more fuel to maintain the same level of performance. Stuttering and misfires can also indicate blocked injectors due to missed strokes.

These symptoms may not always result from dirty injectors. Other engine parts failing can also cause these problems. So, if you want to be certain that it is the injectors that need cleaning, you will need to perform a diagnostic test.

How to Test Your Injectors

Cleaning injectors can be a complex and laborious task, and, if you aren’t mechanically minded, you may damage important engine parts. Save yourself some time and trouble by performing a couple of simple tests before diving in.

To perform these tests, you will need a fuel pressure gauge, an injector tester, and a test light.

Check the Fuel Pump

  1. Locate your fuel pressure port along your fuel rail. Remove the plastic cap and attach the fuel pressure gauge with the correct adapter.
  2. Consult your car’s user manual to check the fuel pressure for your car’s make and model. This is usually between 50 and 60 Psi for most cars.
  3. Turn the key in the ignition to the ON position to prime the fuel pump.
  4. Observe the gauge reading to find the pressure of the fuel pump. Make sure to wait a couple of minutes for the pressure to stabilize before checking the final reading, as the pressure can oscillate.

Check if the Injectors Are Receiving Power

  1. Unfasten the connector for your fuel injector. The method for doing this will depend on your harness.
  2. Connect the test light to the negative terminal of the battery and apply the point of the test light to each of the two injector wires. The test light will light up with each one, indicating there is sufficient power going to the injector and, therefore, it is not faulty or damaged.
  3. Repeat this with each injector.

mechanic troubleshooting car engine

Check the Trigger Circuit

  1. Connect the test light to the positive terminal.
  2. Start the engine and leave it running.
  3. Test the opposite wire.
  4. Check for flashing or flickering, which indicates that the signal is being correctly transmitted to the ECM.
  5. Disconnect the wiring clips from the injectors and perform the test again; reconnect the wire with the test light attached to check that the flickering remains consistent.

If the injectors’ component and power supply are all functioning, the injectors are probably blocked and need cleaning.

How to Clean Fuel Injectors

If tests indicate the injectors are dirty, there are two methods to clean them. However, the easiest, most user-friendly, and often most successful method is to use a cleaning kit.

You will need an injector cleaning kit, air compressor, and fuel pump regulator.


Ensure the kit is compatible with your vehicle and the cleaning solvent is the correct one for the kit. Fill the kit canister with the solvent, and then connect the kit to the fuel port located on the fuel rail.

Disable the fuel pump, and either connect the return tube or a U-tube so that the fuel returns to the tank, and connect the fuel pressure regulator. Then check the fuel pump is inactive by turning over the ignition and opening the fuel cap to prevent pressure buildup.

Connect the compressed air hose and adjust the pressure according to the kit manual guidelines.

Start the car and let it run until all the solvent is gone from the canister.

Unless you are mechanically minded, other DIY methods of cleaning injectors are not recommended, as they can be dangerous and result in engine damage. If your injectors still don’t work after the cleaning kit, they are likely clogged and need professional cleaning.

closeup of car injection system

Final Thoughts

Testing and cleaning your fuel injectors in an important piece of maintenance for your vehicle’s engine—but, as always, prevention is better than cure. If you are not using premium fuel for your vehicle, it is advisable you periodically add a cleaner to your gas tank to prevent buildup from occurring.

If you continue to notice your car performs poorly, it is likely your injectors are worn and need replacing. The best course of action is to take the injectors to a mechanic for bench testing to determine the extent of the damage. Purchase durable, reliable fuel injectors to avoid any future performance problems.

Injector Harness 411

Powerstroke diesel engines have gone in to Ford’s Super Duty trucks, E-Series vans and the Excursion since the mid 1990’s. Initially produced by Navistar, (formerly International Truck & Engine,) Ford took production in-house in 2011, today building the fourth generation in Mexico.

Known for good torque and horsepower, the Powerstroke has been a resounding success. Unfortunately it’s also known to have a few weaknesses, one of which is the injector harness.

The injector harness routes electrical signals to the injectors, ensuring fuel is delivered at the right point in the compression stroke. When those signals don’t get through the affected injector(s) won’t operate and the engine runs unevenly, or not at all. Injector harness problems have been widely reported with the 7.3 and the 6.0 liter Powerstroke engines.

7.3 Engine

The “Check Engine” light will be illuminated and the trouble code is “P1316”, meaning a fault with the injector driver module (IDM). A “Buzz” test will check all eight injectors are working, but not many home mechanics are equipped to do this.

The alternative is determine which injectors aren’t operating, (check the exhaust manifold temperatures,) and examine the harness connection supplying those cylinders. Often the connector will be found to have separated, although sometimes a poor connection has caused heating that burns or melts the connector block.

6.0 Engine

Here the problem is the harness routing. Over time it chafes, eventually leading to failure. Complicating matters, the damage is sometimes internal and not visible to the naked eye. Symptoms will usually be one or more injectors not working (though they will be on the same bank,) or random engine shut-offs due to the harness grounding internally.


While it’s possible to buy individual harness components it’s easier to buy a complete kit including valve cover gasket.

What tools are needed to remove a diesel fuel injector?


Removing your diesel fuel injectors may seem like a job for only a skilled mechanic but the truth is with the right tools, just about anyone with a little know how can remove their diesel fuel injectors. There are a few different tools that you will need to remove the fuel injectors from any diesel engine and with these tools, you can have your engine pulled apart in no time.

The first tool you will need is of course you run of the mill wrenches. This is to remove any covers, protective shields, and more that help to keep your engine enclosed. This type of tool is something that just about everyone has and there should be no reason to buy a new set. Wrenches are easy to come by and most injector covers use standard size nuts and bolts which means that you will not need to buy any special wrenches that are hard to find or useless for other jobs afterward.

The next tool you will need is of course what you will need to take the injector out themselves. This tool is ironically enough called a fuel injector remover. This tool offers a wide range of sockets, much like a ratchet set, that will fit injectors of any size. The set also includes the clamps and bars that you will need to create adequate leverage to remove your injectors. Depending on what company you purchase from, you may also find a simpler, less complicated tool. The less complicated tool is also a fuel injector remover but instead of complicated sockets and clamps, this tool is simply a tube in which you place your injectors then pull. If you feel at any time that you are not able to remove your injectors properly, you may want to call a mechanic to get some pointers.


Install Fuel Injector in Duramax Engine

Duramax engine

Whether you own an older or newer GM Duramax turbo-diesel, you may want to install a fuel injector to replace a tired one. It’s not overly difficult if you have some engine experience. Historically, early Duramax engines were prone to injector failure, requiring frequent replacement.

The Short Version – Steps to Install Fuel Injector on Duramax

  • First, drain the radiator coolant (put aside) and disconnect the negative terminal from your battery.
  • Remove the electrical connector from your air inlet duct on the left side of the turbocharger.
  • Disconnect all electrical connectors from your wiring harness and from the barometric sensor.
  • Take off the engine wiring harness clip before removing the connector for the glow plug controller.
  • Disconnect the crankcase ventilation hose. then disconnect the outlet duct for the air cleaner.
  • Remove the fuel filter and its bracket, along with removing the fuel lines from the injectors and their electrical wiring.
  • Clean away any debris near fuel injectors and fuel lines with a clean cloth or compressed air.
  • Take off mounting bolts for the fuel injector bracket.
  • Use injector removal tool and a flare nut wrench to take out the damaged fuel injector. Examine the injector copper washer and O-rings and replace when necessary.
  • Install the new injector, while fastening its mounting bolts for the fuel injector bracket.
  • Tighten mounting bolts with a torque wrench to 22 foot-pounds.
  • Re-attach injector electrical wiring, fuel lines and fuel line clips. Use a torque wrench to secure fuel line retaining nuts. Tighten to 30 foot-pounds.
  • Re-attach all remaining items by reversing the first six steps that detach these components. Don’t forget to put back the coolant you drained in the first step.

As you can see, the preparation and disconnecting phases are critical to successful installation of fuel injectors. Follow the sequence noted and reverse the steps in proper order to ensure a proper installation.

What is a fuel injection harness?

When it comes to building a custom fuel injection engine or replacing an older fuel injection engine with a newer counterpart, there is one piece of equipment made to greatly simplify the process, a fuel injection harness. This wiring harness is integral piece of your engine installation and is key in the ability to properly supply fuel to your engine.

How to Install Your Fuel Injection Harness

  • Start by positioning the wiring harness along each one of the engines fuel injectors.
  • Once in the correct positions begin snapping each electrical connection into the proper position on each of the injectors.
  • Carefully install the throttle body, paying close attention to each electrical connection.
  • Go back over each one of the electrical connectors to make sure they are securely in place.
  • Lastly, connect the negative battery cable.

Depending on the size and type of fuel injection engine you are working with there may be options available for a customizable fuel injection wiring harness. You can purchase a stock harness or in some cases have a modified harness made for you. A customized wiring harness can be built to accommodate wiring for electronic transmissions, computer controlled fan monitoring, the ability to retain emission components and much more. There are helpful options available to have color-coded wire, labels and convoluted tubing on different harnesses to greatly add to their ease of use during the installation process. When you are undertaking such a big and vital part of the engine installation process these modifications can add greatly to your peace of mind and help you get the job done in a safe and timely manner.