'99 2.8 Vacuum lines

[JKuhn]

I've been trying to find the cause(s) of my '99 TUB28 not running right for some time now, and noticed that the vacuum lines seem to have been misconnected. The issue is, I can't find enough vacuum ports (FPR on the rail, oil separator, SAP and the currently deleted but possibly soon-to-be-reinstalled exhaust valve). I only found enough 3.5mm ports for the FPR and oil separator. So how are they supposed to be connected?

For what it's worth, the FPR was hooked up to the oil separator. But that doesn't seem right to me.

[rf900rkw]

That is correct. The Secondary Air system connection is behind #6 intake runner; well hidden. There are actually 3 fittings there, two of them capped. Hint, the caps rot and fall off. The Fuel Pressure reg is not connected to vacuum, it is VENTED to the same point the crankcase is vented, the CCV system.

[JKuhn]

Ok. That's an interesting one. Everything I found states a fuel pressure regulator should get manifold vacuum.

So then the FPR should go to the oil separator, and the SAP and exhaust flap line to the manifold, with the larger vacuum port sealed off.

[rf900rkw]

M44, M/S52, M62 vent the FPR to manifold pressure for a constant fuel pressure at the injector, making for simple flow calculations.. Starting with the M52TU and M62TU, the FPR is vented to the atmosphere, requiring the DME to calculate and compensate for the variable pressure across the injector. Even later models do regulation inside the fuel tank, often with a variable speed fuel pump. This is industry wide, not just BMW. And all for 0.0001% improvement in evaporative emissions

[JKuhn]

Wait, now you lost me. You said on the M52TU the FPR is vented to the atmosphere. But you said it should be hooked up to the CCV unit?

Oh, and just a side note/question. A previous owner ripped the exhaust apart (decatted, put a silencer in place of the cats which mixed the banks before the downstream sensors, and put a noise maker at the back). I'm now running straight pipes into a second hand stock box, but with the flap deleted. I am however going to get another one with the flap still intact. So should I worry about rotten lines after the vacuum canister? I'm not sure what the canister does, so I don't know if bad lines after it can cause mixture issues (I blanked the line in the engine bay, and took the canister out).