Marcus,
Marcus Frost said:
Dennis,
Basically, he has a fuel pressure gauge which is indicating a drop in pressure in higher rpms (and I am assuming under high boost - *I think* he is running TTC).
This is a pretty key part.. by going down, do you mean it goes from stock pressure (isn't it 38? I don't remember) and falls under boost, or the fuel pressure doesn't raise a 1:1 with boost?
He tried adding an HKS FPR to aleviate the problem (in addition to his stock FPR) but it has been to no avail.
In my experience, the FPR is always the first thing people go to, and 9 times out of 10 the wrong thing.
He does not have the 12v mod and is running a BCC that he tuned by taking his car out and hitting fuel cut then adjusting the screw (not with a voltmeter) until he didn't hit it.
I suspect either he turned the screw enough on the BCC to indicate a vacuum signal on the turbo pressure sensor, causing the car never to switch the fuel pump from 9v to 12v mode, or he wired his BCC improperly and it's feeding the ECU no signal at all (ie, running as if it was a FFCD).
There isn't wrong with adjusting the BCC like that so long as it's in small incriments. (e.g. turn it until it cuts, and then make small adjustments until it doesn't) Through the BCC's design, it's very unlikely it's showing vacuum. I used to know the voltage to pressure scale, but the BCC would have to cap voltage at ~2V for that to be the case. The BCC is a series of opamps designed to allow voltage to pass uninterrupted until the feedback loop of one op amp reaches the input of the signal, at which point the feedback loop becomes output.
Let's assume however the pump never goes to 12V.. the pump should still be flowing enough at 9V to up the pressure. I seriously doubt if 38 PSI (or whatever stock pressure is) just happens to be the limit at 9V.
As far as fuel leaks, I have had MASSIVE fuel leaks where the car maintained pressure and increased with boost. If there is no smell of gas, I suspect one of the hoses in the tank has gone bad and that's where the leak is.
Take out the pump and examine the lines. Or just replace them for good measure.