My FI pump screw does not "click", how many clicks equal one full turn? - PeachParts Mercedes-Benz Forum

Marrs · #1 04-05-2012, 04:28 PM

I'm trying to adjust my idle at "park" since it has the familiar hunting between 700-1,000 rpm. I tried turning the adjustment screw on the back (the one with the spring beneath it) but heard no clicking so returned it to where it was. I marked it and turned it one full turn to be sure I didn't have to go quite a ways to get it to click, so returned it to where it was again, and then turned it 1/4 turn clockwise (total) to see if that helps. Can anyone tell me approximately how many "clicks" per full turn of the screw there should be so I can have an idea of how much I am adjusting?

Marrs · #2 04-05-2012, 04:34 PM

Update: I was simply not pushing the knurled screw head in far enough to engage the screw beneath. Once I played with it a bit I was able to turn it to click. Did 3 clicks to start off with.

mercmad6.3 · #3 04-05-2012, 08:37 PM

Three clicks is the maximum you should turn it. Anymore,and there is something else wrong, sitting thermo, incorrect linkage correlation etc etc .

Marrs · #4 04-06-2012, 12:30 AM

Thanks, I was driving with the 3-clicks richer mode and it didn't do well so I added 3-more (before reading your reply tonight) and it almost died out on idle. I returned to neutral (-6 clicks) and tried 3-clicks the other direction, counter-clockwise, and that settled her right in the sweet spot. She actually needed to be leaned out a bit and also, as an unintended consequence, my downshifts are now butter smooth, no harshness whatsoever. I cannot believe how lovely this car shifts now. I read in my research a post where someone said don't believe it when people tell you these old tranny's are just made that way, they can rival a modern Benz, and low-and-behold he was right. What an incredible machine this car is!

Palolo · #5 04-06-2012, 04:38 AM

When doing the +3/-3 clicks, we're you just relying on idle smoothness and butt dyno, or was there something else that prompted you to want to adjust clicks?

Of course, hearing your experience makes me want to see if a click one way to the other will smooth things out for my car too!

Marrs · #6 04-06-2012, 02:20 PM

Specifically when I was trying to figure out the missing engine issue (turned out to be the coil we discussed) my mechanic found that my throttle plate wasn't adjusted properly. When he did that he also checked timing and exhaust for proper mixture and set everything up so it was perfectly idling. When I still had the miss, he tried to readjust the mixture among other things (fuel filter, plugs) and I noticed it then started to hunt like it used to when i first got the car. Reading through the 113 forums led me to have enough confidence to touch ONLY that part of the MFI system, so I figured if my guy got it to idle properly previously, and that neither the new plugs nor filter could not have a negative effect, I tried adjusting the mixture at the FI pump.

Mind you, you really do need to be sure your throttle plate, rack, linkages, etc., are all in order otherwise this won't do much of anything but cause more headaches. If you are only noticing the hunting at idle, commonly in the range of 700-1,100 rpm in park or neutral, then give it a shot since it is totally reversible and any change will be evident by taking it for a run and testing your adjustments in Park or Neutral.

NOTE: NEVER ADJUST THE FUEL INJECTION PUMP SCREW ON A VEHICLE THAT IS RUNNING, this should be stated in every thread mentioning the adjustment.

Palolo · #7 04-06-2012, 03:37 PM

Ah, I see...

My idle is actually good and steady. It was the effect on the shifting that I was interested in.

Before I touch that, I do need to inspect/verify/etc the trans vacuum connections and solenoid, as I know something isn't hooked up right, since the kick down switch does nothing, and on hills, the car will slow down, holding a gear and downshift very late.

Marrs · #8 04-06-2012, 05:12 PM

My kickdown switch works but I believe on hills I still need to downshift, I don't think it kicks down automatically. I will pay closer attention next time I'm in the hills.
Also check post #3 in my earlier thread, especially the last few notes Mercmad6.3 mentioned about shifting and how these systems all inter-relate.
http://www.peachparts.com/shopforum/vintage-mercedes/314997-car-wants-stall-idle-more-details-included.html