How to

How to bleed a diesel fuel system after fitting new components

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Worried about non-starts or injector faults after fitting new diesel components? Contamination and trapped air are often the cause – and they’re easy to overlook. In this video, our Delphi expert, Phil, takes you through common post-installation issues and how to avoid them.

We’ll walk you through how to:

Identify damage inside injectors caused by air or debris
Avoid contamination during injector installation
Understand different pump types and how they affect bleeding procedures
Use diagnostic routines or manual methods to bleed air, depending on system setup
Safely crank and prime the fuel system to ensure smooth starting
Use the Delphi HD3000 to bleed systems with HPV components

Diesel Fuel Systems How to Distributors Shop Owners Technicians 1 min read

What are the most common injector problems?

There are two main culprits: contamination and air in the system. Contamination damages delicate parts while air prevents proper lubrication, leading to sticking nozzles or failing control valves.

How can I avoid contamination during injector installation?

Keep protective caps on until the injector is about to go into the engine. Exposing the inlet, nozzle, or back-leak ports – even briefly – can allow dirt in and cause damage before you’ve even started the engine.

What is the best way to bleed air from the system?

That depends on the vehicle and fuel system. Some setups allow you to run the in-tank pump via diagnostics. Others require a manual primer. If your vehicle uses a high pressure valve (HPV), you can use the Delphi HD3000 tool to open up the system and purge air efficiently.

What if the system doesn’t have a high pressure valve?

If there’s no HPV, you’ll need to crack open the injector pipes slightly, crank the engine to bleed fuel through, then tighten and torque correctly once fuel appears.

Do I need to worry about electrical connectors when bleeding?

Yes – always keep electrical connectors plugged in. Without a seal, leaking fuel could enter the solenoid and damage the injector beyond repair.

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