ignition - idle - injection pump questions

[merrill]

so,  finally  got the 230 sl started.  now to do some fine tuning.
I have some questions.

Should the idle be set around 800 rpm?  From the haynes manual table has the 250 sl and 280 sl are 750 - 800  rpm.  what is confusing is the haynes manual states that for cars with the constant speed selenoid , when the ac is on or the car is in drive the seleniod should bring the idle up to 700 rpm?  this makes my think the idle should be less thank 800 rpm.

2. dwell should be between 39 - 41

3.  right now the idle is at 800 - 850 rom but it is kept there by the screw on the intake venturi so I need to adjust the idle speed air screw so the venturi can be correctly set. Is this the correct way to set the idle?

4. the haynes manual says the knurled screw on the back of the injection pump is called the idle adjusting screw.  Isn't this really the mixture screw that should only be turned when the car is off?

thanks in advance
matt

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

ok, so

here is what I found,

set dwell at 41 - 42 degrees
set idle at 700 rpm,  constant speed seleniod engages when the car is put in gear

timing seems just a little retarded. (no pun intended) with the vacuum disconnected at 3000 rpm the reading is about 26 degrees not 30.  

checked the co2 with the gas tester I just purchased, it read 9.5? I eventually got the reading down to 6 but I had to turn the inj pump idle screw 5 x.. hopefully this is ok.  If found that when I adjusted the idle the mixture would change.  does one just keep following this process?

so, how do you adjust the timing,  there are 2 nuts, one close to the head that is a 5mm allen screw that appears to hold the clamp and then on the other side of the distributor there is a 10 mm nut with a pointing device and a scale of some sort.  I could not figure it out so I stopped.

So, on the test drive I found a miss when driving at most speeds.
the motor idles well at 700 rpm.  

I will get some new spark plugs, ( I cleaned the old ones) to see if that will help.

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

[ja17]

Hello Matt,

Matt, the golden rule is to make sure the engine is in perfect tune, the linkages and venturi are adjusted correctly and you have a good clean supply of fuel at the correct pressure and volume BEFORE making adjustments to the expensive and complex injection system. Here is some information which may help:



Yes the slotted screw on the intake is the idle air screw. You can use this for your normal idle tweeking. It will add or decrease idle air.

The screw on the injection pump is the idle mixture screw, which changes the low range mixture by increasing or decreasing fuel supply up to about 1700 rpms. This can also be used to addionally tweek the idle and low range.

Your adjustment of five clicks should be fine. Do not move the screw out so far that the click feel becomes faint. Understand however that you are only adjusting one speed range (idle to 1700rpms). If you are leaning up the idle you may still be running rich at all the other rpms above 1700 rpm. These injection systems usually wear rich. In general they run richer as they get older. One easy way to lean all speed ranges out is to remove a shim from under the warm up device. The main rack adjustment screw will also achieve an overall mixture change as will shimming the altitude compensator. Shim removal at the warm up device is the simplest and easiest to put back later without complications.

You can check the other speed ranges by disconnecting the linkage going to the injection pump and work the linkage rods independantly while running the engine after warm up. I have a good description of the process in a previous post somewhere.

Loosening the 10mm bolt at the distributor scale will allow you to precisely adjust the distributor. This nice adjuster was only on earlier W113 engines. Loosening the clamp at the base of the distributor will allow a more radical adjustment. Always push the distributor downward before retightening. A small spring pushes upward and will allow the distributor to disengage if you do not push it back downward.

Check your spark plug wires and ends with an ohm meter (possibly your miss), good idea to freshen up the spark plugs also.

We can elaborate on the above if needed. Good luck.

Joe Alexander
Blacklick, Ohio

[merrill]

Joe,
thanks for the reply

Loosening the 10mm bolt at the distributor scale will allow you to precisely adjust the distributor. This nice adjuster was only on earlier W113 engines. - so, when the bolt for the scale is loose should I be able to turn the distributor by hand ?  I loosened up the bolt and could not move the distributor.  the bolt was so loose that the pointer plate for the scale would flop around.

Check your spark plug wires and ends with an ohm meter (possibly your miss), good idea to freshen up the spark plugs also. - will check these tomorrow.

thanks
matt

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230

[ja17]

Hello Matt,
Sometimes the distributor get stuck  in its holder. Try some penetrant around its base. Moving the pointer on the scale should rotate the distributor in it's holder.

Joe Alexander
Blacklick, Ohio

[enochbell]

You seem to be on the right track, my advice might be overkill but here it is anyway:

The venturi stop screw should be set, along with the linkage, with extreme care so that it allows the venturi to close completely but not bind at idle.  You are correct that the mixture adjustment on the IP should be done only with the engine stopped.  If you are having trouble turning the distributor then it may also need some attention (once you get it free) to make sure the advance mechanism is working.  It can be simple as cleaning and lubricating, but a worn distributor is a sure ticket to frustration...it will likely need a real Doctor.

Finally, be really careful setting the dwell and timing as they are crucial in getting everything else right.  

Congrats on getting on the road!

g

'64 230sl, fully sorted out...ooops, spoke too soon

[merrill]

Joe, G,
so, installed new spark plug wires and bosch wr 9 dc's today and the car runs much better.

sprayed some bp blaster on the distributor clamp a few days ago and it rotated fine.  still need to learn how to use the scale on the distributor clamp.

set the idle ad 31 deg at 3000 rpm.  (will correct later)

looks like I am on my way.

Matt
66 230 sl - "white"
78 300 D - Blue
98 C230