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Author Topic: mixture adjustment for altitude  (Read 4203 times)

bob hall

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mixture adjustment for altitude
« on: January 02, 2007, 17:00:06 »
Our reciently purchased 230sl lived all its life at sea level, where it ran fine, until we moved it to our home at 7000 ft. As a result it now, inspite the best efforts of our german mechanic, runs way too rich & of course, gets terrible mileage. The adjusting screw on the injector pump has been adjusted and just about anything else we can think of has been tried. I should mention the engine in the vehicle is a 280 sl engine. Perhaps some kind soul out there might have a suggestion as to a cure??? We will not move back to sea level.
Thank you for whatever suggestions
                                            doc
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ja17

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Re: mixture adjustment for altitude
« Reply #1 on: January 02, 2007, 23:04:37 »
Hello doc,

Removing the oval shims under the "WRD"  (warm running device) on the injection pump, will lean all speed ranges. If you need the specifics, just let us know.

Joe Alexander
Blacklick, Ohio
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Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Abbas

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Re: mixture adjustment for altitude
« Reply #2 on: January 03, 2007, 08:41:29 »
Joe,
  How does this happen?

What I have learned from this forum is that the WRD engages when the car is warming up and that the thermostat expands as the car warms up and closes the additional air that goes into the car. Then how does the car become leaner if shims were taken out - maybe the opposite will happen because there will be less room for the thermostat to move and the opening will be tighter and less air will go into the system.... I hope I know what I am talking about ... :)

Abbas

280SL W113 1969 Ivory
E280 W124 1995 Silver
« Last Edit: January 03, 2007, 08:42:28 by Abbas »
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Naj ✝︎

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Re: mixture adjustment for altitude
« Reply #3 on: January 03, 2007, 09:33:25 »
doc,
There is also a barometric compensator on the fuel injection pump. It looks like a big black knob on the rear housing of the pump.
This leans out the fuel to adjust for altitude. The diaphragm in it may be tired...

http://www.sl113.org/forums/uploaded/ja17/20031023231515_injection%20left%20illus.%203.JPG


Abbas,
 
quote:
Then how does the car become leaner if shims were taken out - maybe the opposite will happen because there will be less room for the thermostat to move and the opening will be tighter and less air will go into the system....


As the expanding thermsotat closes the air valve, it also pushes on a pin in the air valve and (thru it) a lever in the pump which leans out the fuel intake.

naj

68 280SL
« Last Edit: January 03, 2007, 10:29:27 by naj »
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68 280SL

userzweig

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Re: mixture adjustment for altitude
« Reply #4 on: January 04, 2007, 19:36:29 »
I once was running low on gas during a trip to Yosemite, and all I could get was regular gas instead of high test.  The car felt better with lower octane gas at that altitude, and it might be worth a try next time you run low.

Bruce

1971 Copper 280SL Automatic
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