Fuel Tank is Partly Collapsed

Fuel Tank is Partly Collapsed

The fuel tank of my 86 928S is partially collapsed. Is there anyone on the list who knows how to solve this problem? Any help would be greatly appreciated.

Thank You,

I had the same experience with my 86 928S. The problem was caused by a gummed up valve in the breather line between the Fuel Tank and the Carbon canister located behind the front RH wheel arch. The valve is meant to prevent raw fuel from feeding into the canister and saturating the carbon. However without an effective breather, the tank collapses as the ambient temperature drops and the volume of the fuel reduces.

To fix you will need to drop the tank from the car. I found that by inflating the tank with compressed air and carefully applying hot air from my wife's hairdryer plus some not so gentle persuasion with a large rubber mallet, the tank returned to its original shape and has held its shape for more than a year now.

You must, of course, clean the vent valve which you will find behind the RH rear wheel arch protector. Just wash with clean fuel and air dry.

Allow at least one day for this job. It is time consuming but you shouldn't need any new parts. Good luck.


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