How to Bleed an Injector Pump

hand on a fuel injector
What You'll Need
Car mechanic tools
What You'll Need
Car mechanic tools

All diesel engines have an injector pump that is connected to injection fuel lines. The injector pump helps pump fuel into the diesel engines cylinders at a very high pressure, around 15,000 Psi, so that the fuel can be slowly injected into the combustion chamber. Whenever there is excess fuel, it is used to cool down the injectors and is then returned to the fuel tank with the help of valves. During this process, air bubbles can be formed in the injection system if the engine is running on low fuel or if there are fuel leaks in the injection lines. For smooth engine function, it is important to bleed an injector pump of any air so that fuel can easily flow to the combustion chamber. This step-by-step guide will help you bleed an injector pump easily. The tools and materials required for the job are given below.

Step 1 - Check Fuel Lines

The first step is to ensure that all the lines of the fuel system are installed correctly and that there is no dirt-clogging causing irregular fuel flow. After doing that, all the lines between the combustion chamber and the injector pump must be checked for fuel leaks. Any tiny fuel leaks in the lines can cause air bubbles too.

Step 2 - Remove Valve Cover

Most diesel engines have their fuel lines covered by a valve cover. Remove that valve cover to have easy access to the fuel lines that connect the combustion chamber to the injector pump.

Step 3 - Open Fuel Cut-off Valve

fuel line inside the engine

To do this, use a wrench to open the fuel bolt of the last injector in the fuel injection system. On most diesel engines, the last injector is the forward-most one. You can refer to your car's manual to confirm which injector is the last one. Be extremely careful when working on the injector pump as causing a break here can lead to the high pressure fuel coming out at you. The fuel is at such a high pressure that it can penetrate human flesh and can cause serious injury.

Step 4 - Bleed the Injector Pump

Now that the major fuel connections from the combustion chamber to the injector pump have been opened, put the fuel control position to 'No-fuel'. After doing this, tip the engine over by using an engine mount with chains. Do this very carefully with the help of a friend as engines are really heavy and dropping it onto yourself can cause serious injury. When you tip the engine over, fuel will start pouring from the last injector that you took off the bolt from. Observe air bubbles while the fuel falls to the ground. As soon as you notice a smooth fuel flow without air bubbles, use a wrench to put back the bolt tightly on the last fuel injector. You have successfully bled the injector pump.

Step 5 - Finish the Job

After finishing this job, there will be a mess on the floor as you spilled fuel on it. Clean it up with rags, sand, or kitty litter and dispose off properly without endangering yourself or others.