I have recently been experiencing slightly jerky power delivery from my vRS, after a poke about in the engine I found that the vacuum pipe which runs from the inlet manifold to the fuel pressure regulator had a split in it. I must have damaged it when I fitted a t-piece for my boots gauge. I have repaired the damage and all now seems well, it will be hard to say 100% that the problem is cured until I have driven the car a bit more but it certainly didn't misbehave when I took it on a 15 mile run just now. Does the fault I have found sound like a realistic cause of jerkiness?

My other question is, what would happen in the event of the hose bursting all together? I'm guessing the car would still run?

Thanks

Yep, you wont be getting full fuel pressure under load.

basically the fuel pressure regulator has a stiff spring inside a sealed chamber which has a set tension. noramaly around 2.5-3 bars or a road car. the spring prevents the pressure from exceeding that level by bleeding off the excess pressure back to the fuel tank via the return hose, the vacumm hose is connected to the sealed chamber and effectively reduces the fuel pressure by the same amount of vacuum present in the engine, and in the case of a turbocharged engine increases the pressure by the amount of boost present...

still folowing?? so theoretically at idle( assuming you have 100% VE:D ) you would have a manifold vacuum of -14.7psi(-1bar) so you are using a 2.5 bar regulator your actuall fuel pressure at the injectors will be 1.5 bars..... and likewise if you have a boost pressure of say 7psi(approx 0.5 bar) your fuel pressure at the injectors when using a 2.5 bar regulator will be 3 bars...

and because of the way fuel injectors vary thier fuel delivery rates at different operating pressures at certain points in the rev range you will be underfueling, and at other your will be overfueling... if you have an fsi engine you needn't worry because iirc they have a fuel pressure sensor on the fuel rail to counteract this possiblity...

so without blinding you with science the answer to your question is

yes the car will still run without the hose in place, but........

1. the fueling will be 'off' at certain places in the rev range

2. there will be an increased idle speed due to the added air bypassing the throttle body through the hole where the hose is supposed to be attached

sorry, but i'm really really bad at explaining stuff like this:O

here's a pic i pulled off google to help you understand more about how it works