hi all apologies for my first thread being an ask for help !!

[MidlandsNick]

I am trying to fix a car for a friend, a beetle in on a W plate petrol non turbo and it has some very odd symptoms
When its running at tickover the car runs absolutely fine, but as soon as you touch the throttle its like its got no fuel ? just lots of induction noise and a refusal to rev at all
if you feather the throttle a bit you can eventually get it to rev but its not clean and has misfires everywhere..
we had a code read done on it and it picked up a few which were cleared but the fault still remains even though the engine still misbehaves, the only way it can be made to run right
is to clamp the fuel return pipe, then it will rev almost perfectly..
I have so far
changed fuel pressure regulator on injection rail
checked for air leaks on inlet (found massively loose bolts on the 4 branch inlet manifold that goes OVER the engine)
checked fuel flow, it filled a litre jug in about 5 seconds and seemed a good strong flow of fuel
checked air filter
changed fuel filter
a second code read after the above revealed nothing out the ordinary but in depth shows low voltages on the middle two injectors compared to the outer two injectors???
many thanks
Nick

[Flash2]

Hello Nick, welcome to the forum.

Have you done a fuel pressure test to see what pressure there is on the rail? Measuring fuel flow without measuring the pressure is no good. A defective pump might easily push fuel through an open pipe because that doesn't take much work but it might not be able to build pressure which puts the pump under load.

I know this doesn't tie in with it running better with the fuel return line clamped off but for those sort of symptoms I'd have been thinking about the possibility of a blocked exhaust before I even got to checking fuel delivery.

Jim.