I think CJ is correct. There are metal lines to the injectors, but there is also the "bypass" line that goes from injector to injector which is fabric coated rubber and just slips over a nipple. These do deteriorate and will then leak raw diesel fuel. It is very easy and very cheap (less than $5) to get the hose, cut it, and put it on in about 5 minutes. Don't forget to get the rubber plug that goes aver the very last injector. I keep a few sections of this hose in my glove box at all times.