TECH TALK: Supplying Fuel from the Injector

In order to get the most power out of your truck, it needs to efficiently supply high pressure fuel from the pump or rail to the injector inlet. You will find the injector inlet connector tube, or fuel supply tube, located through the side of the cylinder head.

The fuel supply tube is sealed to the injector with metal-to-metal in order to withstand the torque rate. Otherwise the diesel engine will experience a high-pressure fuel leak if the wrong material or improper torque is used. Often you will recognize the root cause of the fuel leak being inlet surface deformation or a small gap in the metal-to-metal seal. With a fuel leak comes injector misses. And with injector misses comes low engine power.

Usually a bad fuel injector will produce a few symptoms to look out for:

1. The engine misfires and there is a noticeable decrease in power, acceleration, and fuel efficiency. This is the most common symptom of a potential fuel injector problem. In severe cases the engine may even experience stalling or the inability to run at all.

2. You smell diesel fuel. Injectors hold high pressure that can sometimes leak over time at the nozzle or at the seal located at the injector’s tip. A leaky injector will send excel fuel into the engine chamber, while a leaky seal will allow fuel to seep into the base of the injector. Both can affect engine fuel efficiency and performance, and often produce a noticeable fuel smell. If you smell fuel, address it as soon as possible to prevent a possible safety hazard.

3. Your check engine light turns on. Clogged fuel injectors that misfire or experience an electrical issue will trigger the check engine light. Of course, there are myriad engine management issues that can also trigger the light, so you should scan your truck’s computer for trouble codes to be certain.

Between the fuel tube fitting and fuel injector, a fuel supply tube edge filter provides protection from contaminants. The filter blocks particulates larger than 10 microns to avoid damaging the fuel injector assembly. Unfortunately, edge filters cannot be accessed to clean or replace, so once its damaged the entire fuel supply tube needs to be replaced.

It’s highly advised to check the condition of the fuel supply tube O-ring and replace as necessary any time you have access to it. When you’re installing or replacing it, spend a few moments to inspect the fuel supply tube O-ring so you don’t have to replace it later. We recommend you consider replacing the O-ring as preventive maintenance to ensure a perfect seal all the time. And while you’re at it, inspect the entire fuel supply tube for any signs of damage or wear so you minimize the chance you’ll need to disassemble the fuel system again in the near future due to misfiring or decreased power.