I've used a syringe successfully with slightly diluted PVA in the past:
December 2012: loose kitchen chair spindle backs. I had to do all six as we were expecting big people to stay for Christmas! I couldn't knock them apart, as the good joints were really solid.
I used the largest gauge hypodermic I could find (0.3mm or 0.4mm, IIRC), and used a wheel brace to drill into the void below the tenons from under the seat with a very small drill (0.5mm I think). I kept pumping until I could see it weeping round the socket. Using a wheel brace you could just about get into the right place and still avoid the back legs of the chairs.
It worked OK on most of them, but a couple came loose again after a few months. I need to try again soon, but I'll use Titebond II this time as it'll set faster than ordinary PVA.
We have a medic in the family, who can get hypodermics occasionally (expired stock etc.). They're really handy for getting wallpaper glue into air pockets, precision oiling of mechanisms, and feeding the Christmas cake! The syringes are useful for measuring two-part polyurethane too - it attacks the rubber seal but lasts long enough for about three batches a day apart, after which it's too sticky.
Doing the chairs, the PVA did leak a bit round the needle, as it wasn't a snug fit in the hole. I'll try sealing round it with blu-tac next time, or possibly try to get a better match between needle and drill. Also it might be worth drilling a second small hole to stop it airlocking (some joints were tighter than others). I can't remember if I used a pin chuck - probably did, as 0.5mm is really too small for a standard one.
And I think I blunted the needle on an oilstone first, to stop it catching in the hole (they are very sharp otherwise).
E.
