How to Find a Fuel Leak

Raise the vehicle and support it on jack stands. Using a flashlight, trace the fuel lines from the tank to the engine. Look for evidence of the leak, to include spots with a greater accumulation of dust and road grime, wet spots or streaks and clean spots where the fuel washed away all of the grime. If you find evidence of fuel dripping from a frame member or other structural component, follow that member to discover the source. Bear in mind that gravity, as well as wind pressure, can affect the path of travel and the fuel may be running along a series of members before it drips out.

Several products are safe to add to your gasoline or diesel fuel to help locate the source of a fuel leak. Essentially, these products contain a dye that will glow under florescent or ultra-violet light. Check the instructions for the dye to see which type of light makes it visible. Add the dye to the fuel and run the engine so that it leaks some of the treated fuel, then perform a visual inspection with a hand-held light. These products are available under brand names such as Cliplight Incorporated Multi-Purpose Dye, Gas-Glo 32 by Spectronics Corporation and AutoPRO Dye by Interdynamics, among others.

Some leaks can be well hidden and defy attempts to find them visually. In these cases, use a device known as a leak detector to zero in on the source. The device has a probe that you insert into areas that aren't readily visible, and it detects the presence of compounds within both gasoline and diesel.

Fuel leaks can be very dangerous when left untreated. The most obvious danger is the possibility of a fire or explosion, but fuel can cause other damage as well. Both gasoline and diesel will attack and degrade the rubber in your tires, as well as any rubber bushings in the frame. It can also damage the finish on painted sheet metal, as well as any plastic components it contacts. Do not delay in effecting repairs once you determine that you do indeed have a fuel leak.