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engine:gasventtube

Gas Vent Tube

Well, if you're familiar with the smell of gas in the cockpit of your Esprit, you probably need to replace the gas vent hose that is known to eventually deteriorate.

You may have even wondered how the smell finds its way into the cockpit area. Vapors can find there way into the cockit thru the upper seatbelts recoil units, which sit right over top of the fuel tanks. In other cases it finds its way into the door sill cavity via cable and hose penetrations in the bulkhead. Thats why you can smell fuel out of the seatbelt slots.

Replacing the gas vent line was pretty straight forward, but finding the vent line proved to be a bit tricky. As I was soon to discover, the gas vent line is actually a series of vent lines that work their way from the left hand driver's side gas tank filler neck and over the engine bulkhead, into a “t” piece, which then branches out to the Roll Over Valve and to the right hand passenger's side gas tank filler neck.


It is worth noting that on some US Federal cars, a fuel vapor recovery catch tank is included in the system. The catch tank is mounted above the right-hand side fuel tank. The vapor tube from the fuel filler pipe is connected to the catch tank, and the outlet tube from the catch tank is routed via a roll over valve to a connection tee on the charcoal canister.

The vapor recovery catch tank system collects vapor from the fuel tanks, the vapor is then condensed into liquid fuel and residual vapor. The catch tank inlet fitting extends down a distance into the catch tank and controls the maximum level of liquid fuel in the catch tank. Any increase in level above this tube allows fuel to be drawn back into the fuel tank. It is worth noting that the catch tank could be nearly half full of fuel at any one time.

The tubes leading to this catch tank also deteriorate, however the problem can be greater than just fuel vapor. A split or loose fitting tube on the catch tank can allow liquid fuel to leak out into the area surrounding the fuel tank. This can become a fire hazard as well as a nuisance. Once the lines are renewed, the fuel smell may take a few weeks to clear as the fuel dampened areas air-out.

It is worth pondering how important the catch tank is, considering the added fire risk it poses.

A good replacement tubing to use on the fuel vent is 1/4“ ID clear urethane tubing. It looks identical to normal vinyl tubing we see every day, however it is very tough, fuel proof, and durable. You can get urethane tubing a most performance plastics shops and some professional outdoor power equipment suppliers. Some shops carry a brand of tubing called “Tygon”. It is clear yellow in color and has similar properties to the clear urethane type.


I replaced these series of lines as they were both badly deteriorated and gas fumes would continue to come through as long as were not both replaced. The vent lines I replaced are illustrated as the black colored lines in the diagram below; the longer line represents the vent hose that runs across the engine bay bulkhead and connects into the left hand gas tank, and the shorter line represents the short run from the “t” connection to the right hand gas tank:

To start, you need to first unscrew and remove the carpeted rear quarter trim panels that are located to to the right and left of the engine bay struts. Then pull down the carpeted area above the rear bulkhead; this will expose the gas vent line. Continue pulling down the carpet to follow the vent line into the trim panel areas. The picture below shows the carpeted area pulled down and the red arrow points to the hose; this picture was actually taken after the black replacement hose was installed.

My hose was so badly deteriorated that it came out in pieces; you can see the old vent hose which is a clearish tan color, and the new replacement vent line already in place. The replacment hose I used was black fuel grade gas line from my local auto parts store…

Once I fished the new vent line in place of the old vent line, I connected the vent on the driver's side into the fuel filler neck connection. This requires advanced contortionist skills and the ability to stand on your head for about an hour. The toughest part was removing the old vent hose and clamp as it's located up in the pillar next to the fuel cap. I used a small screw driver to loosen the hose clamp and razor blade to cut old line just enough to pull it off the filler neck connection. Be careful not to drop any old hose or hose clamps as the cavity below as it seems to be a fiberglass no-man's land accessible only to spiders and small mammals. And remember to thread on the hose clamp BEFORE connecting the hose! Photo below shows the finished connection into the left hand side fuel filler neck.

I connected the right side of the vent hose to the “t” piece by feel as it is mounted up in the right side pillar near the passenger side gas tank and is tricky to remove. I also replaced the badly deteriorated line from the “t” piece to Right Hand passenger's side gas tank filler neck using the same flexibility skills I developed earlier in the project. The right side connection is shown below.

Once replaced, the gas smell went away completely. I used contact cement from the local harware to glue the carpeting and hose back into the bulkhead. *Alternatively, 3M make a great professional quality spray-on contact adhesive available in aerosol cans. Check your local professional autobody materials suppliers.* I reinstalled the rear quarter trim panels to complete the job. The remants of the old vent line can be seen below:

engine/gasventtube.txt · Last modified: 2022/09/09 20:54 by 95.111.247.252