Author Topic: External Air/Fuel Idel Adjustment  (Read 4453 times)

Mhastings

  • Guest
External Air/Fuel Idel Adjustment
« on: November 18, 2013, 20:37:40 »
I have been trying to adjust the air/fuel adjustment valve on the back of the injector body it does not seem to want to turn CCW OR CW what could the issue be? Can it be repaired short of a complete rebuild?

garymand

  • Inactive
  • Gold
  • *****
  • USA, CA, Meadow Vista
  • Posts: 537
Re: External Air/Fuel Idel Adjustment
« Reply #1 on: November 18, 2013, 21:01:14 »
The adjust ment screw that sticks out the back of the FIP is gas only.  cw is more gas at idle.  It is not really the adjustment screw.  The real adjustment screw is inside.  This screw is just a link to engage the real screw.  You have to push the outside screw in by about 3 or 4 mm (1/4in) and find the screw slot to engage the internal screw.

It is a 3 step process: 1) push the screw in
2) find the and engage mthe internal slot.
3) turn the internal screw some number of clicks.
Gary
Early 250SL German version owned since 71, C320, R350, 89 Porsche 944 Turbo S

Basil

  • Guest
Re: External Air/Fuel Idel Adjustment
« Reply #2 on: November 18, 2013, 21:10:37 »
@Garymand.
Please tell Mhastings to stop the engine before step 1 ::)

garymand

  • Inactive
  • Gold
  • *****
  • USA, CA, Meadow Vista
  • Posts: 537
Re: External Air/Fuel Idel Adjustment
« Reply #3 on: November 18, 2013, 21:47:16 »
Sorry, I don't think about that anymore.  It has become part of my 'common sense.'   ::)  Hmm, maybe that's what happened to the O-ring in  the parallel thread that was broken in half and missing part.  Jaming the screw all the way back just might do that.

"Wise men learn from other's mistakes.  Smart men learn from their own."
Gary
Early 250SL German version owned since 71, C320, R350, 89 Porsche 944 Turbo S

ja17

  • Full Member
  • Platinum
  • ******
  • USA, OH, Blacklick
  • Posts: 7414
Re: External Air/Fuel Idel Adjustment
« Reply #4 on: November 21, 2013, 14:56:48 »
Hello mhastings,

Make sure the engine linkages are correct first. Do "The Llinkage Tour".  These injection systems "wear" rich with age.  But you need to find out if when your system is running rich. Cold, hot, at idle, mid range, high range,at acceleration  or all of the above? Read about "The Split Linkage Test" to help determine if your system and when your system is running rich.

Yes, the thumb screw on the back of the injection pump is for low range fuel adjustment (idle and up to 1700rpms). It must only be adjusted when the engine is off and it is engaged by pushing in on the knob, engaging the slot and turning. It will "click" as it turns. The idle air adjustment is the large slotted screw on the intake manifold. Spend some time searching up the information on these items on this site. Once you determine what is going on, we can help you adjust the injection correctly.

The Pagoda Golden Rule..........  "Before altering the expensive and complex injection system, make sure you have a perfectly tuned engine, a tested WRD, a leak proof starting valve, correct engine linkage, and a clean fuel supply with adequate pressure and volume".

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