Expert: Roland Finston - 9/1/2011

Question
I just read your answer to a similar question. But I wanted to ask about gas fumes near the rear of my '99 Jeep 4.7 4x4. I've noticed the fumes for several months, not real strong, but noticable to me. Then on a trip back from the Smokies I got the check Engine lite. Is this where I should start looking for the leak?

Answer
Hi Rob,
If there is an emission sticker on the underside of the hood that shows the vacuum hose layout that would be a useful roadmap to follow. Basically there are rubber hoses with clamps that connect the top of the gas tank where fumes collect to a set of devices that colleet the fumes in a charcoal-filled canister and in a controlled manner feed them back into the intake manifold.
So it is a matter of item by item checking all those hoses and their clamps/fittings at both ends until you find the source of the fumes. I only have an '06 Jeep manual set on CD and would wonder if it is applicable to your earlier model. But that is basically the idea. You will find parts of the system at the top corner of the fuel tank and then you would also follow the hoses to a recycle control device, the hoses to the canister (which may be at a front corner of the engine compartment), and a hose from there to the intake manifold. You would look from under vehicle for the items associated with the tank, and from both above and below the engine compartment for the balance. There also is a hose from the neck of the filler tube (just below the gas cap seal) to the top of tank that you would do well to start at, looking from under the fender at the filler point, particularly because you smelled fumes most strongly at the rear. That vapor hose might be the site of the leak, at either end.
Roland