Help! - vacuum in 3.2 fuel tank

[jkeith]

I'm struggling to find any information that might help to cure this problem.

Every time I fill up with fuel, when I release the filler cap there is a huge suction of air into the fuel tank.

I am aware that this should not be the case but expected that this would not be a fault that hasn't happened before on other cars.

My first suspect cause is the pipe connecting the expansion chamber to the evaporation chamber. A diagram in the Clymer workshop manual indicates that there is a Restrictor fitted on this line. Can this be faulty and somehow acting as a non return valve? If so, where is this fitted on the car?

Has anyone any knowledge or experience of this fault? Please help if you can, any assistance is appreciated.

Cheers.

 

[Luddite]

Hope this might help..

https://www.impactbumpers.com/forum...-tank-breather-system-in-a-backdated-32-1984/

 

[jkeith]

Thanks Luddite.

The white plastic expansion chamber connects between the filler neck and the top of the fuel tank. It also connects to the evaporation chamber and this line has a restrictor (?). Vapour should be able to flow through this pipe in either direction.

The other connection off the evaporation chamber connects to the carbon canister. The engine fan draws air through the carbon canister.

I suspect I have either got a kink in a pipe or a blocked carbon canister.

It seems like a bit of a challenge as most of the pipes are not visible. I think the carbon canister is housed in the OSR wing and the white rectangular expansion tank and black evaporation chamber are under the NSF wing.

The restictor is currently my prime suspect by the very nature of its function. I havn't looked for this on the car yet as I was hoping to see where it was fitted and what it looks like on a PET diagram or similar.

Keeping my fingers crossed that the fault will be easy to find and rectify.

Cheers.

 

[Luddite]

Never had to deal with fume filtration systems, though your description of the system shows a degree of understanding, and the logic of your thought processes works for me. I guess you may be experiencing running issues perhaps as the fuel pump struggles against the vacuum it is creating... A whole lot of gubbins to reduce petrol fumes getting into the atmosphere.. You could of course cheat and let them escape, but I admire your tenacity to keep things working as they were designed to...Good luck in resolving the issue.. :thumb:

 

[jkeith]

Update:

Finally managed to solve the problem! Thanks to a process of elimination by the guys at D&G, the fault was identified as a blocked pipe within the centre tunnel.

This is a very small diameter steel (?) pipe and not easy to access without stripping out the interior, gear lever, etc. Poking a wire down the length of the pipe eventually cleared the blockage.

No more vacuum in the fuel tank! Fantastic!

Cheers, Keith.

 

[Luddite]

Many thanks for the update Keith. Great that your issue is resolved. Seems a strange place for a blockage to occur.

Should you wish to view inside the tunnel I will post the link of a vid to give you an insight.

https://youtu.be/Ov5WgnuHffE