fuel pressure question

[jfoj]

Originally Posted by upallnight

Everyone I know calls it a vacuum line to the fuel pressure regulator.

See 3:00 in this video

https://www.youtube.com/watch?v=8t-6raUI8vs

or this guy in this video

https://www.youtube.com/watch?v=btOIaDdhJHA

Why don't you post the BMW documentation since you must have read it.

Attached below is a PDF of page 35 from ST055 MS43/MS43. This is a Service Training document from BMW.

This cover Models:
E46/E39/Z3 - MS42 with M52TU Engine
E46/E39/Z3/E53 - MS42 with M54 Engine

SPECIAL NOTE, the document is a bit misleading because it does not CLEARLY separate the FPR setup for the MS42/M52TU from the MS42/M54.

The LAST paragraph and the picture at the bottom of the page is relative to the MS42/M52TU, NOT the MS42/M54. I think this is pretty obvious to anyone that pays attention to the MS42/M54 and to the fact that the hose on the FPR is NOT connected to the "cyclone oil separator" AKA CCV, but is connected to the intake boot.

Everyone calls it a "vacuum" line because it uses rubber "vacuum" hose. BUT for the M54 they are ALL wrong. They are technically referring to the "rubber tubing" as "vacuum" line or hose and of course, if it is called "vacuum" line, it must have "vacuum" present. But for the M54 this IS NOT the case.

But if anyone uses their brain, it is stupid obvious that there is NO manifold or venturi vacuum between the air filter and the throttle body butterfly. Would love to see someone figure out how this may happen. It will ONLY happen if the air filter is so restrictive that it will not flow air unrestricted into the intake. If the air filter is so badly restricted that manifold vacuum would be present in the intake boots, they would likely collapse and the engine would not even run.

I could also care less what anyone on YouTube or the Internet has to say. If they would just take a second and think about what happens to the air before the throttle body butterfly valve I think the situation would be pretty obvious. The work "vacuum line" is being tossed around incorrectly, these should have stated the rubber vent hose, but they obviously do not understand the fuel system they are working on or at least have not thought about the system and chosen their words carefully and accurately.

Additionally if anyone would take a second and disconnect the "vacuum" hose which is really just a rubber hose that connects to the FPR they would see in about 2 seconds there is NOT 18-20+ inches/manifold vacuum at the connection on the intake boot at idle.

There is a lot of misinformation that is continually perpetuated on a daily basis. This is just one of the many things that people get wrong and nobody ever gets corrected. I am trying to set the record straight, educate people and get them thinking for themselves.