Tool Briefing Recognizing and addressing GDI ISSUES While Gas Direct Injection has improved since the early adoption of this technology, carbon buildup can still be an issue shops must address. By Barry Hoyland, Contributing Editor Less than 10 short years ago, the technology which is most widely known as Gas Direct Injection (GDI) was being used on under 5 percent of the cars being built. Due to stronger requirements to meet CAFE (Corporate Average Fuel Economy) standards mandating vehicle manufacturers improve fuel economy of their entire fleet, its use in 2015 went up to approximately 45 percent of gasolinepowered vehicles in the U.S. The utilization of GDI is expected to approach 70 percent over the next few years. With any new technology, there can be growing pains where early systems can have issues that later changes overcome. In the case of GDI, improvements to the systems have not only overcome many early problems, but have also improved the effectiveness of the system and further increased fuel economy. In order to understand GDI and the differences in diagnosing drivability concerns with it versus traditional fuel injection systems, it is important to be familiar with the basics of a GDI system. VEHICLE AFFECTED: All vehicles with gas direct injection (GDI) 72 PTEN OCTOBER 2016 www.VehicleServicePros.com Traditional late-model Port Fuel Injection (PFI) systems utilize a pulse width modulated low-pressure fuel pump (typically under 50 psi) without a fuel return system that prevents hot fuel returning to the tank. Fuel injectors receive this fuel through a common fuel rail, and then distribute fuel into the intake port where it mixes with air while being delivered to each cylinder through its intake valve. Most GDI systems use a pulse width modulated low-pressure pump just like a PFI system. The difference with GDI is that the low-pressure system delivers fuel to a camshaft-driven high-pressure pump where the fuel pressures can be increased to as high as 3,000 psi. This fuel is then delivered to injectors that are placed directly into the combustion chamber. The high-pressure fuel is mixed with air in the combustion chamber rather than the intake manifold thereby atomizing it better, allowing more complete combustion as well as improved fuel economy. This process allows for a leaner overall air/fuel mixture that is burned without creating excessive emissions. Newer versions of GDI systems are relatively free of trouble, while some of the earlier versions had significant issues. Most of the problems with GDI stem from carbon buildup in the intake system. There are a few notable instances of other issues with GDI systems, mostly related to the high-pressure pump. We will be discussing some of the common issues and how to best utilize the necessary tools to diagnose the problem. The primary symptom of GDI system issues tends to be rough idle after starting. p The BG VIA Vehicle Injection Apparatus allows technicians to deliver the necessary additives or cleaners to the fuel injection system - including both PFI and GDI applications. The difference is the type of cleaner added to the system, based on company recommendations. p The BG Air Intake System Cleaning Tool, No. 9209, an attachment used on the BG VIA apparatus, finely atomizes BG GDI Intake Valve Cleaner for safe, effective cleanup. Circle 214 on card, or enter at “e-inquiry” on VehicleServicePros.com TOOLS USED: • Scan tool • Fuel pressure tester • Vacuum gauge • Lab scope with pressure transducer • Borescope • Combustion and fuel system cleaners • Approved solvents for carbon cleaning
Professional_Tool_And_Equipment_News_October_2016
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