Using a fuel injector cleaner tool on a car with a return-style fuel system can be tricky. This guide outlines the challenges and offers potential solutions based on experience with a 1998 Volvo S70 T5. The tool in question uses air pressure to force cleaner through the fuel injectors via the fuel rail while the engine runs, requiring the fuel pump relay to be removed.
This process worked successfully on a 1999 S70 GLT with a non-return fuel system. The key is to set the air pressure lower than the fuel pump pressure to prevent cleaner backflow to the tank. 40 psi was used on the 1999 model. However, applying this method to the 1998 S70 T5 with a return-style fuel system resulted in a vibrating noise, engine failure, and the entire cleaning fluid being pushed back through the return line and fuel pressure regulator.
The return line in the 1998 model creates a pathway for the cleaner to bypass the injectors and return to the tank. This highlights the critical need to understand the fuel system pressure at idle for the 1998 S70 T5. Knowing this pressure is crucial to setting the correct air pressure for the cleaning tool. Too high, and the cleaner bypasses the injectors; too low, and the engine won’t run.
Accessing the Schrader valve on the 1998 model also presented a challenge due to the cable-based throttle mechanism. Removing the valve core and using an open-ended fuel hose adapter with a clamp provided a workaround to clear the throttle cable bracket. A 90-degree connector might be helpful in this situation.
The failed attempt on the 1998 S70 T5 underscores the importance of knowing the fuel rail pressure at idle for this specific model. Successfully using this type of fuel injector cleaner tool on a return-style fuel system requires precise pressure adjustments. Without this information, there’s a risk of damaging the system or wasting cleaning fluid. Further research or consultation with a Volvo specialist might be needed to determine the correct procedure and pressure settings. Understanding the nuances of different fuel systems is paramount for effective fuel injector cleaning.
