Idle Fuel/Air Adjustment

[Klaus Pieper]

Hello,
Although my 1965 230 SL Automatic is running very well, I would like to tune the idling more accurately using the procedure as outlined in the Manual.  The vacuum port on the throttle seems akward and the diameter of the port is only 4mm, making it difficult to find (or make) a suitable fitting for the vacuum gauge.  My question: can one use the port for the brake booster vacuum line on the inlet manifold as an alternate port for the vacuum gauge?

Your views are greatly appreciated.

Regards, Klaus

[stickandrudderman]

Yes, or another option is to use the port for the vacuum line to the transmission.

[Klaus Pieper]

Thank you very much for the quick response.  I will try it out.

[Klaus Pieper]

Hello again,

I have attached the vacuum gauge to the brake booster port, as my vacuum gauge hose fits there perfectly.

The vacuum reading changes very little, between 0.2 and 0.4 kPa, when screwing the idle air valve in or out.  Is that the ball park figure?

My second question refers to the fuel injection pump brass knob at the back of the fuel injection pump.  Should this knob turn easily when pushed in or is there a quite a lot of resistance and can this knob be over turned or stripped?

Regards, Klaus

[Pawel66]

You have to read through this anyway: https://www.sl113.org/wiki/Restricted/Linkage-tour

In Idle Fuel/Air Adjustment section it is described in detail how this adjuster turns. It turns freely, you need to push it in, turn it a bit to find the slot that engages the screw and then it turns with clicks. When you look at how adjusting screw looks like, you will understand what I am talking about. It is necessary to read this passage called Linkage Tour.

[Klaus Pieper]

Thank you Pawel,

I have read through and performed the "Linkage Tour" on a number of occasions previously, but I had never adjusted the fuel injection pump adjustment screw before. The adjustment screw free wheels nicely, but on pressing it forward and once in its "click position" is very hard to turn clock-wise or anti-clock-wise and hence my question.

Regards, Klaus

[Pawel66]

I see.

You know from the pictures that it is located between two spring leafs that do the clicks. I had something what you described once when the screw was turned too much in. What I did is to remove the cover of this adjusting section (in older FIPs thewre is this big nut to unscrew) to see/fix the adjusting mechanism. Not sure if it is necessary in your case.

[Klaus Pieper]

Thank you Pawell.  I will follow your advice and have a look at the turning mechanism, there might be a problem there.  Once I have checked this, I will report back.

Klaus

[Cees Klumper]

Yes, this screw should move freely once push-engaged. If it's stuck, your idle air-fuel mixture may be off (potentially by a lot).

[Pawel66]

There is an o-ring between that adjustemnt screw and plate. may want to replace it when you are there.

[Klaus Pieper]

Thank you, both Cees and Pawel.

The adjusting screw does certainly not move freely and since I applied a little force, oil is seeping very slightly from where the adjusting screw enters the fuel injection pump body.  Am I correct in saying that the oil reservoir seems to be just behind the cover plate? In other words the oil should be siphoned out of the fuel injection pump before removing the big nut?

The 230 SL has the big 42mm nut which needs to be unscrewed to get to the adjusting mechanism.  I do not have a 42mm spanner and I am not keen to use a shifting spanner in restricted space.  I need to do a little more research before proceeding.

I would be grateful for any further advice or comments.

[Pawel66]

You may want to do some search, e.g. this: https://www.sl113.org/forums/index.php?topic=24059.msg172347#msg172347

maybe you have a shop nearby where you could borrow a 42mm socket?

[Klaus Pieper]

Thank you Pawel, you are a star!  That link is a great help.