Adjusting the full range rack screw

[wwheeler]

I posted back in 2010 about questions on how to adjust this screw on the back of the pump. I now have a new update on how to do this and have yet to find it on this site. My pump is a R20Y US. It has both the starting and fuel cut off solenoid.

The issue was that when I removed the cap screw leading to the rack adjustment screw and inserted a slotted screw driver into the hole, I hit a spring loaded lever. I could never engage the screw. The suggestion was to remove the starting solenoid above and that would make it easier to see the rack screw. Well it did increase visibility, but I still could not insert a screwdriver through the hole and engage the rack screw because of this lever. The lever turns out to be the one that the starting solenoid contacts to richen the pump. 

I contacted a friend of mine in Germany who professionally rebuilds these pumps and asked for help. I have a two plunger pump on my 220SE and know there is a screw on the side of the pump that will move the lever out of the way. Turns out this pump has the same screw although is on the opposite side, the side facing outward. It is a cap screw with a 14mm hex. Loosen it out almost where it touches the lever on the pump. Behold! The rack screw is now exposed!

Now inserting the slotted screwdriver you can feel the screw and easy to click in either direction. Just tighten the 14 mm hex back up and you are in business. With this tip, removing the starting solenoid is not necessary and didn't really help all that much.

Yes, you can do the same by changing shims on the BC. My problem was I needed to lean the pump and only had the factory 2mm hardened shim. No way to go smaller unless I made new ones. That factory shim is hardened and a special size to fit in a recess. I didn't want to go there. I just now need to adjust the idle speed knob and i'll be back in business.   
       

[Pawel66]

Thank you for sharing!

[BobH]

I've just added this to the tech manual

[wwheeler]

Thanks for adding to the manual. I can barely run my I-Phone. Hopefully it is helpful and was surprised that lever never came up or at least I couldn't find anything about it. Maybe the pumps vary and some do not have to deal with the lever. I just know that on my pump, the lever had to be moved in order to access the rack screw.

Thanks.

[ja17]

FYI Wallace, McMaster Car carries 14mm diameter hardened shims in various thicknesses.

[wwheeler]

Thanks Joe! Mcmaster is one of my favorite places. I didn't think to look there. BTW, I was looking at a 230SL 6 plunger pump the other day. The access to the rack screw has a much larger hole than mine on the 280 pump. With the larger hole, yo may be able to get at the screw without moving the lever.

[rosch]

 @ wwheeler / mrfatboy

@ wwheeler :Owning a 230SL with a R11 FIP I removed the screw at the back of the IP to gain access to the rack adjustment screw.
Looking inside the hole there is the tip of the  enrichment lever obstructing access to the adjustment screw.
In the TM /injection pump section wwheeler is mentioning a 14 mm bolt on the outside of the pump .
Loosening this bolt should  move this lever aside for easier access . I tried this just a couple of turns and the lever moves !
My question is : is it safe to turn this bolt as mentioned a couple of mm without risking of parts falling out or getting loose,
in other words how far can you go ?

Maybe helpfull :
Attached I added 2 edited photo's from the TM pointing out the 14 mm bolt . The second photo with the rear cover removed shows partly the mentioned enrichment lever which - when flipped down- is obstructing access to the adjusting screw. Maybe someone has a better picture with the lever in place ?


@mrfatboy suggestion : maybe something to add in the TM ?

[wwheeler]

My understanding is that you can unscrew the bolt until it stops. Maybe about 3 or 4mm. Nothing will come loose. I know, I was extremely anxious about doing that for fear a spring would go boing out of the pump. Nope, nothing happened. I would unscrew until it gives you the clearance you need and stop.