Q&A

Ask Away! with Jeff Smith: Finding & Fixing a Strong Gas Odor from a 1967 Chevy El Camino

I normally park my 1967 El Camino in my separate shop with all the other car parts and stuff but recently had the opportunity to park it in my attached garage next to the house. The house was immediately saturated with gasoline fumes so the car had to be quickly banished back to the shop, where the smell isn’t nearly as bad—or maybe I just don’t notice it as much. We parked a friend’s 1968 Camaro in the house garage a while back and it did not stink up the house. Is there something I can do to minimize the smell?

C.D.

We’ve had a similar experience with certain early cars smelling of gasoline more than others. Let’s start with the obvious things and look for a minor leak that may only occur when the fuel tank is near full. These early GM cars used a rubber O-ring seal between the sending unit and the fuel tank that may have deteriorated to the point that it leaks, but only when the tank is near full. So clearly the first solution would be to ensure there are no external leaks.

A larger issue could be a combination of the fact that the factory used an open vent tube and a vented cap for the tank. It’s possible that the factory vent tube that runs alongside the filler neck is cracked or broken. Another consideration for a station wagon or El Camino is a rubber connector between the steel tank and the fuel inlet tube. If the rubber connector is cracked or broken, this could cause the smell and you might not notice it if the crack is near the top of the hose where liquid fuel may not contact the hose while refueling.

One consideration that we will have to guess at is your car’s stance. If the car uses large rear tires or has a dramatic front to rear rake with the body higher in the rear than the front, this will force fuel forward, bringing fuel closer to where the vent tube is located. Most fuel tanks employ a small “vent dome” near the vent to create a pocket of air close to the vent tube to prevent fuel from being pushed out in hot climate conditions. A forward rake could cause the vent to leak.

Most GM passenger cars from the 1960s used a long vent line that runs vertically out of the tank up into the trunk area then does a 180 degree turn back through the trunk and exits underneath the car. It’s possible that if this 180 degree tube is damaged or missing that fumes could escape from the tank and cause the problem. One theory is that, since gas fumes are heavier than air, this long vent tube prevents the fumes from leaving the tank but do vent the tank when the engine is operating and fuel is drawn from the tank.

It’s also possible that, if your car is equipped with extended runs of regular rubber fuel line, fumes could escape from these lines. While liquid fuel will not leak through the lines, it is possible for the vapors to exit the hose. To this end, there is rubber fuel line that creates a vapor barrier. Earl’s offers a Vapor Guard rubber fuel line for both carbureted and EFI applications in both 3/8 and 5/16 inch diameters (see parts list at the bottom of this post). This hose is designed with a specific liner that prevents fuel vapors from escaping. 

We wrote an entire Buyer’s Guide on flex fuel hose to help you build the right fuel plumbing system. Click here to read it.

If after finding no leaks but the fuel smell continues, you might consider adding a carbon canister to the vent package. Newer cars in 1972 began adding this filter to store vapors in this carbon canister until they can be purged with a solenoid. For a carbureted application, you could just vent the canister to the atmosphere since this becomes the vent for the tank.

We’ve also run across an interesting product from a company called II Much Fabrication. The company makes a billet aluminum vapor separator that can be mounted in the trunk and is completely sealed. The separator uses a large threaded fitting (approximately two inches in diameter) that bolts to the trunk. Inside this area is a -8 orb fitting that is connected to the vent on the gas tank. The second outlet is a small brass style filter that allows the tank to vent. A friend built a hot rod that suffered from a nasty fuel smell while driving the car and this vapor separator helped solve his problem. This unit is not inexpensive, but it may help solve your fuel smell issues.

Ask Away! Earl’s Fuel Line Parts List

This is the sending unit area of a typical 1960s GM fuel tank. The sending unit is sealed with a large rubber O-ring (arrow indicates where it would be located). If the seal is old, it may have cracked and allow the tank to leak. This area is certainly worth checking to make sure there are no leaks. (Image/Jeff Smith)

Tags: , , ,

Leave a Reply

Your email address will not be published. Required fields are marked *

*

This site uses Akismet to reduce spam. Learn how your comment data is processed.