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What's your fuel pressure? (archive)
[ Follow Ups ] [ M5 (E28) Message Board ] [ Msg. Board FAQ ]
Posted by Todd Kenyon on January 28, 2002 at 14:58:08:

Installed a FP gauge when I replaced my fuel lines. It reads about 45 psi at idle and cruise, drops to 36 during coastoff, jumps to 50 psi if I pull the FPreg vacuum hose off. 45psi is higher than non-M engines (around 40). I was wondering if anyone knows if this is normal for the S38.

I also noticed that the vacuum that the FPreg gets is only 9inHg at idle, vs the usual 15-22 inHG. The readings at the individual tbodies is around 18inHg as expected. So either the vacuum port to the fpreg is clogged, or there is a resrtictor in there. I have heard a few others say that their vacuum is also 9inHg, so it may well be normal. But if it was supposed to be 18, that would lower the fuel pressure to the 40 psi range seen in other engines. Anyone have any insights as to whether this is normal? Maybe the S38 needs higher fuel pressure so the way to get it is reduce the vacuum by about 50%?

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