Leak detection of the fuel pumps can mainly be observed by symptoms, including the perception of fuel odors, reduced fuel efficiency, and spots of fuel under the vehicle. Normally, fuel odors mean leaks since gasoline has a low flash point at about -45°F; even a little leak in it can create a smell. It would be important to do a good check around the fuel pump and lines because worn-out seals, cracked hoses, or corroded connectors may facilitate leaks, especially in higher-mileage vehicles whose parts get worse with time.
One symptom or way to confirm that there is a leak is via the increased fuel consumption. Some cars with fuel pump leaks tend to have around a 10 to 15% increase in fuel use due to the fact that the system loses fuel that never reaches the engine. Another way could be more frequent refueling, especially amidst other symptoms. The mechanics often recommend placing a piece of cardboard under the area overlying the fuel tank overnight; any appearance of fuel spots by morning confirms the presence of an active leak.
Using a fuel pressure gauge is a further step toward detection. Most fuel-injected systems run within the range between 30 and 60 psi. A drop lower than this bracket may indicate a leak, considering other components are healthy. If the pressure readings are always falling, then one should look at where the leakage is happening in the fuel pump or its surroundings.
A smoke test can be done if it’s not visible and pressure tests show nothing. Most repair shops do smoke testing, which simply pumps smoke through the fuel lines and the tank to find even minute leaks through visual means as the smoke escapes the damaged sections. Very effective, it usually reveals leaks that may not be otherwise apparent upon routine observations.
Quick identification and repair of leaks in the fuel pump prevent the loss of vehicle performance, fuel efficiency, and safety. For more information about maintenance and replacement of fuel pumps, see Fuel Pump.