Tuning the RPM after and engine mounting change

[Abbas]

I justed wanted to share my experience with other members...

After fixing the mounting on my Tommy (280SL 1969 Auto)
the car needed tuning especially that the RPM now
is not like before. It is running smooth when on the
highway but when you stop on a traffic with gear on drive
the RMP would go down very low - unless you put Neutral.
 
So I took it to the mechanic and he started playing with
all those screws that affect the RPM.
 
We found near the air filter there was a small spring
that holds the accelerator - actually there were two of them
please see picture (1) . So we took one out and kept the original -
and amazingly it solved the problem and also it made the accelerator
pedal was much lighter than before - This extra spring most probably
was put there for some reason before and forgotten.
 
Actually we tried first to play with the Solnoid (circle 2)
and every time we pressed it and put gear on drive
the RPM would be in good position and would not go down
and this is how we discovered the two springs because they
are related to the solinoid through a number of rods.
 
Then the RPM on Neutral or park needed tuning and this is where he
played with screw # 3 in pics which affects air flow. Also there
was a small screw underneath the distributor that would affect the
RPM as well - this other one provides more/less electricity to spark
plugs he played a little with it then brought it back to its previous
position.
 
Tommorrow I shall take Tommy for a long ride and see how things are
now.

I advise all members to check their engine mountings and gear bushings
when I changed those on my Tommy the car ride became much smoother and much more fun.


Download Attachment: TngRPM2.JPG
66.66 KB

280SL W113 1969 Ivory
E280 W124 1995 Silver

[ja17]

Hello Abbas,
It sounds like you may need to start with a basic linkage adjustment first. See the "injection pump tour" just posted.

After the linkage is correct, try adjusting the air screw #3 (in your picture)to control idle.

The engine should idle in gear should be nearly the same as the idle out of gear.

Report back and we can go from there.

Joe Alexander
Blacklick, Ohio

[rwmastel]

It is worth making note that your mechanic was starting with good adjustments.  Some mechanics start with adjusting the fuel injection pump, and that should be a last resort.

Listen to Joe's advice and check the adjusted length of all the linkage rods.  Also, check that the ball joints on the ends of the linkage rods are tight (not loose and rattle).

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420