Fuel Pressure - BMW Luxury Touring Community
 
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post #1 of 5 Old Jun 10th, 2009, 6:44 pm Thread Starter
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Fuel Pressure

I rode home 1100 miles from Vermont a week and a half ago with the bike running such a rich fuel mixture I was only getting around 30 mpg. I just fired it up after replacing the spark plugs and O2 sensor. It sounds and idles fine. It also revs up good when you twist the throttle. By the time I got home it wouldn't idle or rev up good.

I hooked up a fuel pressure gage between the pressure side of the QD fittings and it reads 80psi. My Clymer manual shows it should be 50.78 psi. Should I assume the fuel pressure regulator is bad?. The manual doesn't show a min. or max psi that is ok?.

Dave Selvig
2004 Black LT
2000 Canon Red LT



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Last edited by saddle-man; Jun 10th, 2009 at 7:22 pm.
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post #2 of 5 Old Jun 10th, 2009, 7:19 pm
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Re: Fuel Pressure

Quote:
Originally Posted by saddle-man
I rode home 1100 miles from Vermont a week and a half ago with the bike running such a rich fuel mixture I was only getting around 30 mpg. I just fired it up after replacing the spark plugs and O2 sensor. It sounds and idles fine. It also revs up good when you twist the throttle. By the time I got home it wouldn't idle or rev up good.

I hooked up a fuel pressure gage between the pressure side of the QD fittings and it reads 80psi. My Clymer manual shows it should be 50.78 psi. Should I assume the fuel pressure regulator is bad. The manual doesn't show a min. or max psi that is ok?.
EDIT: Wait a minute -- where did you hook up the gauge? Pressure is supposed to be 50 psi *at the rail* -- the comments below may be N/A if you are measuring pump output -- that's the whole purpose of the regulator -- to take a high incoming pressure and provide a regulated pressure to the fuel rail while bleeding off the excess back to the tank.

80 psi is way too high, and the symptoms match your pressure regulator suspicions. The regulator is at the rear end of the fuel rail, above the head. I'm not sure about this, but my memory is that there's a circlip securing the regulator components to the rail. I've never had a reason to take one apart, but because I'm a cheap *******, before I went to the dealer looking for parts I'd depressurize the fuel rail, pull the clip and see if I can figure out what's damaged inside, in the hope that BMW would me sell only the appropriate part, not a whole new fuel rail.

Good luck!

Mark Neblett
Fairfax, VA
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post #3 of 5 Old Jun 11th, 2009, 5:29 pm Thread Starter
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Re: Fuel Pressure

Quote:
Originally Posted by mneblett
EDIT: Wait a minute -- where did you hook up the gauge? Pressure is supposed to be 50 psi *at the rail* -- the comments below may be N/A if you are measuring pump output -- that's the whole purpose of the regulator -- to take a high incoming pressure and provide a regulated pressure to the fuel rail while bleeding off the excess back to the tank.

Good luck!
The manual says to hook up a tee fitting between the QD fittings. I don't see any where to check pressure on the rail. I have good flow and no pressure on the return line. Just in case I'll install a new pressure regulator tomorrow.

Dave Selvig
2004 Black LT
2000 Canon Red LT



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post #4 of 5 Old Jun 11th, 2009, 7:04 pm
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Re: Fuel Pressure

Valerie and I are following your diagnostics and are relieved you made it back to NC safely. We just returned from our ride to VA Beach. It was wonderful. Wish we could have met down in your neck of the woods. Stopped in Atlantic City on return and won the cost of the ride.

Hope you discover the problem and post on NE forum. Everyone was concerned for your safety.
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post #5 of 5 Old Jun 11th, 2009, 7:42 pm Thread Starter
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Re: Fuel Pressure

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Originally Posted by BigGeo
Valerie and I are following your diagnostics and are relieved you made it back to NC safely. We just returned from our ride to VA Beach. It was wonderful. Wish we could have met down in your neck of the woods. Stopped in Atlantic City on return and won the cost of the ride.

Hope you discover the problem and post on NE forum. Everyone was concerned for your safety.
Good to here you had a nice trip George. The last time I was in Atlantic City we were racing offshore power boats. We got done working early one night & as we walked into Trump Plaza Donald was walking out. One of the kids with us said to Donald i've never been to a casino how does it work. Donald said get out your wallet and open it up give me all of your money And leave.

Dave Selvig
2004 Black LT
2000 Canon Red LT



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