When i installed my Bosch 040, i extended the cables a little bit by soldering some extra on. I used heat shrink over the solder join, i checked the pump a few days later, and the heat shrink was still there. It should be fine, i got it from Supercheap Auto. If you really are concerned, get a glass jar, put some petrol in there with some heat shrink, put the lid on, and leave it a few days and see what happens.