You're right it only fertilizes half of the day, no reprograming is necesary the timer just keep going
As I tried to explain in the original post, I made a sleeve with a piece of PVC pipe, this is where you place the screws and attach the syringe, I forgot my camera today but I'll add some photos tomorrow.
With this kind of timer you can't dose 8 ml, the logical way was to use a 10 ml syringe which I tried (also tried 5, 20, and 60 ml), but is not reliable, it gets stuck frequently due to the lack of power from the small timer motor, if you can find a bigger one (like gpodio suggests it may work), this small timer can work with 1 and 3 ml syringes, they can deliver 0.1 to 0.7 ml (1 ml syringe) and 0.5 to 2.4 ml (3 ml syringe)
You should try with different sizes and brand names, not all of them work, some stuck quite easy (BD), for me Terumo worked, but I don't know if we have the same products
Another idea, if you find a bigger motor, why not 2 opposing syringes? (Like a BMW motorcycle engine) it may work and you have all day dosing, or dosing 2 different fertilizers
As you have already noticed, English is not my mother tongue, so feel free to edit the post, saludos desde Guadalajara
By the way I haven't seen yet an American (U.S.) posting in Spanish, why don't you try ? http://www.drpez.net/panel/showthread.php?t=68288