yesterday i attempted to change mine, due to my skoda cube not starting well when cold. I managed to get the one nearest the passenger side changed, but I am at a loss as to how I can get the other 3 out, without having to remove a load of other parts, namely the injectors + fuel lines. If I were to remove them, would i have to prime the fuel pump when refitting?

I've no experience with derv engines, which is why i was reluctant to remove them.

On a plus side my van now starts much better even though I've only changed the one plug so far!

If you remove the injector pipes, then usually you need to bleed them when you try to restart; this is easily done by loosening off the union at the injector end and cranking the engine til fuel comes out - make sure you've wrapped a rag round the union so the fuel doesn't go everywhere and most importantly doesn't get in your eyes or skin (don't hold it too tight) - it's at very high pressure. Do that for each pipe, then it'll be fine; sometimes (not often) it's possible for the air in the pipes to compress and make it difficult to get it started and therefore bleed after being dismantled. The pump itself shouldn't be a problem though, I've never known one let air back into it significantly when doing this (there's always a first time, mind!). There's no need to over-tighten the pipes when replacing them either, they need to be tight (obviously), but you can over-do it (as I've seen on a couple of engines, leading to damaged pipes)

yes you need to remove the injector pipes (be thankful its not a golf as you need to remove the pump too )

once the pupes are refitted leave the injector end slack and crank the starter for 20 seconds or so then tighten the pipes onto the injectors and crank again untill it starts..

ok thanks for your help! will give it a try