The Audi A5 has been a popular compact coupe since 2007. Most motoring journalists favorably view it. However, fuel system problems sullied the model’s reputation. Most, but not all, of these snags are traced to a defectively-designed fuel pump.
The fuel system must deliver a proper mixture of air and fuel to the engine for efficient combustion. The job of the fuel induction system is to provide the engine with a correct air-fuel mixture in all driving ranges from idle to wide-open throttle.
An electric fuel pump delivers gasoline into the combustion chamber of your Audi. It’s engineered to be long-lasting, but like any part, it can fail. That’s when replacement becomes necessary.
Here are the indicators of a bad fuel pump in your Audi:
- Engine “chokes” or struggles to maintain speed
- Noises, backfires, and a sputtering engine
- Hesitation when starting or accelerating
- Any of the above issues, along with a “Check Engine” light
In the 70s, the federal government established fuel mileage and pollution standards. Fuel injection became the norm because it was the only technology that allowed manufacturers to meet the new requirements.
Fuel injection requires a high-pressure stream of fuel to the injectors. Fuel is pushed from the fuel tank by the electric fuel pump. Pressurized fuel is sent to the fuel filter and the injector rail. A fuel pressure regulator controls the system’s fuel pressure.
Under load, when the intake manifold vacuum drops, the regulator maintains higher fuel pressure to compensate. At idle, where the intake manifold vacuum is elevated and fuel can enter the cylinder more quickly, the regulator compensates by lowering fuel pressure. A bad regulator can cause poor running.
There is a control module to provide fuel pump power. If this part fails, the result will be hard starting, poor idle quality, and lack of energy. Burned spark plugs can result from operating with a lean air-fuel mixture caused by a malfunctioning control module.
The delicate pieces of the fuel injection system require clean fuel. Modern Audis have a fuel filter intended to last the car’s life. However, using contaminated fuel will cause the filter to bypass, sending dirt to the pump. We will check the filter for undue contamination, leading to fuel filter and pump replacement.
Today’s engines typically last longer than 150,000 miles; fuel pumps often have shorter lives. We can usually remove the fuel pump through an access hole in the fuel tank, but in some models, we must remove the fuel tank from the vehicle. This is a time-consuming but necessary procedure following fuel pump failure.
Fire can result from a fuel hose leak. We should inspect fuel hoses often since regular hose replacement is prohibitively expensive on modern Audis.
The final link in fuel delivery in modern systems is the fuel injector, installed near the intake valve. A sequential fuel injection system opens each injector just before the intake valve opens. The system can quickly adjust the fuel mixture to maximize fuel mileage and minimize pollution. Inputs from the camshaft and crankshaft position sensors instruct the computer when to fire individual injectors. The most common problems with fuel injectors are leaks and clogging.
Common Audi complaints relating to the fuel system have included:
-Cracked fuel pump housing discovered by the dealer
-Bad fuel delivery hose from the pump to the fuel rail
-Leaking fuel injectors causing cylinder misfires and even engine stoppages while driving
-Fuel pump failures.
Our ASE-certified technicians will quickly diagnose your Audi’s fuel problem and get you back on the road for many miles of safe motoring.
