Originally Posted by MrEngineerdat

Hi guys,
My friend has a sierra 1.8 with the pierburg 2e carb on it. Unfortunately, the carb has had to go on a diet ages ago, because external diaphragms weren't working, but we managed to get the internal diaphragm replaced, so we have the squirt diaphragm. But never the less, its been able to run fine until recently, - when we decided to get the head off, skim it, port it, and throw it back together. We didn't immediately adjust the carb any... I do appreciate that the compression ratio is now different, by some 40thou skim, which gives us 200-210psi on cranking. I've been cautious of trying to keep her running in good order, checking plug colours and electricals connections and such, and vacuum leaks too, there aren't any. Pipes are all connected.
It was discovered that the air filter could be cleaner, so for testing and adjusting we've been trying to cure without it.
But she still insists on running rich with the mixture screw completely closed off.
I have heard from somewhere and I noted it ages ago that the passive fuel pressure regulator, on the inner wing, is susceptible to delivery problems. Can anyone confirm this? it seems odd to me that it would over pressure to the carb, but maybe i'm missing something.
Can anyone suggest anything?
Many thanks in advance