How To Test The Fuel Injectors (Ford 5.0L And 5.8L V8 Engine)

Checking If The Fuel Injector Sprays Fuel

If the 'dead' cylinder's fuel injector passed the resistance test, there's a chance that it's clogged and not spraying fuel. I've had this happen to me before quite a bit, where the fuel injector's internal resistance was good, but it was clogged and causing its cylinder to misfire.

Many years ago, finding the clogged fuel injector was quite the involved process. It went something like this:

1. Remove the intake manifold plenum.
2. Swap out the fuel injector with a neighboring one.
3. Put everything back together.
4. Crank and start the engine.
5. See if the cylinder misfire has 'moved' to the cylinder where I installed the 'dead' cylinder's fuel injector.

If the cylinder misfire moved to the 'dead' cylinder's fuel injector's new location, then I can be 100% certain that the fuel injector is clogged (even tho its internal resistance was OK).

In this day and age, there’s a tool that significantly simplifies the process and it doesn't cost an arm and a leg. And if you’ve already removed the intake manifold plenum from the engine, you’re halfway there.

The tool is made up of the following two components:

• A fuel injector power module: This module allows you to connect the fuel injector to your vehicle's battery and activate it by pulsing it.
• A plastic adapter: The plastic adapter allows you to connect the fuel injector (after you've removed it) to a spray can of brake cleaner.

Once you've set up the fuel injector (on the brake clean spray can with the adapter), you then use the power module to 'pulse' the injector. This allows the brake cleaner to flow into fuel injector and get sprayed out of it. The beauty of it all is that you'll be able to observe the fuel injector's spray pattern in real time.

If the fuel injector is clogged, its spray pattern will resemble more of a squirt rather than a fine spray, or it won't spray at all.

I've used this game-changing tool myself a few times, and man, I wish this would have been available since 30 years ago! You can see it and buy it here:

Important Tips For Removing The Intake Manifold Plenum

If you need to remove the intake manifold plenum to access the injectors underneath, there are a few important things to consider:

1. Be careful that no foreign object, like a bolt, a nut, or any metal piece/part, falls into the open manifold port runners or you run the risk of engine damage if you start the vehicle.
2. Once the plenum has been removed, place a clean rag or rags on the open intake runners. This will keep things from falling into them.
3. As you're removing bolts, nuts and stuff from the intake plenum to remove it, place them in a container and away from the engine compartment.

If anything falls into the open intake ports (runners) without you knowing it and you crank and start the engine, you're gonna be in a big world of pain!

If this happens, the only way to remove the object is to remove the cylinder head. So be alert and be careful. Removing the plenum isn't an out of this world thing that nobody can or shouldn't do, you just have to be careful (heck, even just crossing the street has risks!).