Testing for a Malfunctioning Diesel Fuel Injector

August 8, 2022 5:29 pm Published by Leave your thoughts

If you’re realizing a poor performing diesel engine that used to run a lot better, especially at low speeds and idle, then what’s likely going on involves plugged up or gummy fuel injectors. While these parts and assemblies have revolutionized how engines work, as well as made them far more fuel efficient, fuel injectors are also prone to needing manual maintenance after a while. That’s because the microscopic channels that make their function work so well tend to get gunked up with residue and carbon over time. When that happens, the mist that travels through the injector to the combustion chamber doesn’t work well, and the engine performance suffers accordingly.

Symptoms Appear Before They Are Seen

In most cases, a clogged engine is going to give itself away quickly since the fuel delivery isn’t working properly. Common symptoms tend to include poor starting or running at low speeds, mentioned above, as well as an inability to throttle up quickly and lots of smoke coming out of the exhaust. More often than not, the check engine light will come up on as the sensors get flooded with a fuel/air imbalance and a good amount of fuel will get wasted, producing an abnormal consumption rate.

How to Test Diesel Injectors with a Multimeter

While it might sound complicated, using a multimeter to see if there is sufficient charge to operate an injector is very simple. A multimeter’s purpose is to confirm that there is a clean circuit from one point to the other. The engine should be off, and the electrical connectors unplugged. The multimeter scale should be set to Ohms to measure resistance. The probes should be connected with the electrical connectors on the injector, and the scale measurement should be tracked at the same time. If there is a difference in resistance from what should be seen, then there is an issue. If the resistance is not showing anything and contact is confirmed, then the coil is short circuiting.

How to Test Diesel Injectors

There are a number of ways to test whether a diesel engine’s fuel injectors are failing, and some work really well without having to disassemble everything prematurely. The first is sound. Most folks who’ve been around a particular engine know how it sounds. When things are running right, there is a very familiar hum. Injectors work the same way; when operating correctly, they click as the assemblies open and close. If there’s no clicking, that’s a bad sign of clogging. Even with the engine noise, the clicking can be verified either with a stethoscope or with a long rod touching the fuel injector. The vibration of the clicking will travel through the rod to the listener’s ear.

How to Test Injectors for Leak Back

Another problem that can contribute to improper operation will be if the injectors are leaking. Normally, the assemblies should be sealed. But if they have gaps, diesel will find a way out quickly. A simple paper towel test confirms this. Place it under the injector and turn the ignition so the engine system is on but the engine is not turning over yet. Leakage will show up on the paper towel as the injectors become primed for starting.

How to Test Diesel Injectors at Home

As mentioned earlier, heavy smoke and thick smell of emissions is also a sign of an injector problem. As they malfunction, too much fuel gets delivered to the engine, particularly at idle. A diesel system smoking the place up via the exhaust probably needs to have the injectors cleaned out and maintained again quickly.

There’s No Quick Fix, Unfortunately

Ultimately, if there is a problem confirmed with one of the methods above or symptoms, then the fuel injectors will need to be disassembled and cleaned out, as well as bad consumable parts replaced entirely. Fuel injectors don’t clean themselves, even with a hot running engine. In fact, temperature just bakes in the residue and lets it build, making the problem worse. Instead, the injector has to be removed, completely taken apart, inspected for worn parts, rebuilt and re-installed. This is a typical complete cleaning for a diesel fuel injector. While it is possible to flush them out with the injector still installed using a solvent, it won’t achieve a full cleaning the same way that a rebuild will.

For fleets and operators who need regular injection cleaning service without hassles and high-quality reliability, Thompson Diesel Services has been a market leader for years. Diesel injection maintenance and rebuilds are standard fare for our technicians, and our consistent delivery has been the reason both keep coming back to Thompson again and again.

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