I have a 2005 3Litre S type with a fuel filler flap which will not close. Upon investigation I found that a screw had appeared to have come out of its position. Attempted to put the screw back in and closed the flap. The screw just fell out again. Any ideas on how I could fix this? The screw does not look like the original part.

Hope the attached photo's make things a little clearer

Opened fuel fuel filler flap




Mechanism to hold the fuel filler flap




screw that has come loose to hold the fuel filler flap closed

 

Looks like that screw has been used to replace the white plastic latch pin that typically cracks and fails on many of these S-Types (mine included). Years ago there were several discussions here on the forum about finding an appropriate metal pin instead of the flawed plastic pin, but I never saw a follow-up report of anyone actually being successful in doing that. The metal pin needs to be the same size and shape of the plastic pin and while it looks to me that your screw comes close, it is not quite perfect and years of opening and closing the lid finally popped it out. If you can manage to glue it back into place, it may hold for quite some time....

The key with the plastic pin is to keep it fully lubricated with white lithium grease at all times so the latch mechanism functions with as little friction as possible. If you manage to glue your screw back into place, I would keep it lubricated in the same manner. That should prolong its willingness to stay exactly where you put it....

 

It's a common problem. I had mine replaced.

 

Correct. Replace it with the proper part and then keep it lubricated after that.
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Many thanks for the all the advice. I ended up taking the car to my service man and he replaced the part. Works fine now. Will keep it well lubricated.