Fuel filler cap leaks fuel

[jastx]

My stock 1977 2500M filler cap leaks fuel when the car is driven. The spring-loaded inner seal is still pliable and appears to seat correctly and firmly. Is this a common problem? The previous owner had the original steel gas tank replaced with an aluminum one, I don't know if it is baffled or not but I'm sure my issue is related to the fuel sloshing around. Perhaps the seal, though still pliable, is no longer soft enough.

My previous, older 2500Ms had larger gas caps I liked much better so I bought a used TR6 gas cap in nice condition. The photo below of another gas cap like mine includes a metal ring I don't have. Is this piece required or does the stock gas cap I will replace also come with one I could reuse?

Finally, any tips on the removing and replacing procedure?

Thanks!

[Slow M]

Some of the filler necks have a cast-in overflow/vent pipe. A rubber hose attaches to it. This is often missing or broken. Also, inspect the rubber pipe connecting the filler neck to the tank for cracks.

Best,
B.

[moluag]

The large rubber washer appears on the American TR6, but was not on my Tuscan V6. I don't believe it was fitted as OE on TVRs.

The metal ring should be present, but it is purely cosmetic, only tidying up the underside of the base of the filler.

[JeffT]

I recommend you inspect the fuel filler hose and clamps. I am having a similar problem with my 2500 and the upper hose clamp was loose. I replaced the hose and clamps. Double clamped the hose on the tank side because I had room... and the hose I got was one of those flexible ribbed radiator hoses.

[Slow M]

JeffT said:

I recommend you inspect the fuel filler hose and clamps. I am having a similar problem with my 2500 and the upper hose clamp was loose. I replaced the hose and clamps. Double clamped the hose on the tank side because I had room... and the hose I got was one of those flexible ribbed radiator hoses.

Please make sure the hose is formulated for fuel!!!

Best,
B.

[jastx]

On closer inspection, the TR6 assembly is complete with the metal ring. However, I looked at my existing assembly inside the body this weekend and the two are significantly different. The '77 has two tubes connected to it -- one to the tank, the other to the vapour separator. The TR6 has none -- one vent cast into it but not drilled on the outside.

Any advice on making this swap would be appreciated. Can I eliminate and plug either of the existing hoses? Or should I just leave it and not swap?

Apparently the force of the gas sloshing is causing my leak problem, the force overcoming the seal. My tank was replaced by the previous owner and is aluminum but apparently not baffled. Is there a creative solution that doesn't involve replacing or baffling the tank , perhaps a one-way valve of some sort that I could add to the rubber hose section between the filler neck and gas tank?

My other two 2500Ms with the large gas cap and original gas tanks did not have the gas leak problem. Were those thanks baffled? I need to solve this somehow.

[moluag]

jastx said:

The TR6 has none -- one vent cast into it but not drilled on the outside.

Not a lot of use having a vent in the cast but not drilled outside. This is what the base should look like.

[Geoff38]

Could You use something like this ?

http://www.demon-tweeks.co.uk/Motorsport/Fuel_Syst...

Cheers
Geoff.

[jastx]

As ingenious as it seems...I think not.

[jastx]

Here is my gas cap. Appears it only needs drilling and tapping.

[jastx]

It is vented...