throttle linkage adjustment

[jmbour]

With time, the accelerator pedal of my 1971 280SL got more and more play. I have to press it almost half its course to get the negine accelerate. Of course, with full pressur on it, I get the throttle half open. The problem seems to be with the progressive linkage (described in the "linkage tour" of the technical forum) : at rest, the roller of the progressive linkage sits at the bottom of the lever. So when the linkage rod coming from under the intake manifold goes up, there is a 5 mm play,  the lever does not move immediately, and does not move enough to open the throttle fullly.

I understand that the linkage rods should be adjusted before tampering with the accelerator pedal adjustment (13 mm head bolton the left side of the car).

Is it possible to adjust the length of the linkage rod between the block pivot and the intake manifold lever ? Is there a standard length for this rod ? and will this solve the problem ?


Thanks for your help

[Naj ✝︎]

Hi,

There is a rubber bush in the throttle linkage near the firewall (and very close to the exhaust on a LHD car)
This could have deteriorated or broken up.
Worth checking first.

naj

[jmbour]

Hi naj

The roller is not broken , but seems worn.
I intend to replace it but don't think it will be enough.
jmb

[ja17]

The slots for the roller can wear and enlarge causing excessive movement in the linkage. The linkage rod from the block pivot is adjustable. You can try to adjust it some to make up for the slop in your linkage.  Making it longer will give you more throttle to make up for the slop in the progressive linkage. This cure may  be a temporary fix.  You will need to repair or replace the worn parts to get best results.

[jmbour]

Thanks Joe.
I am pleased to get advice from an expert.
I will first try to adjust the rod, and plan to replace the triangular lever (part A1300700022 ?)
Thanks a lot
JMB

[ctaylor738]

From the pedal to the throttle arm and pump lever, it's all metal-to-metal.  Hard to see where that much play could come from except from the large bushing down at the bottom.  There is a small plastic bushing where the triangle lever attaches.  It might have deteriorated as well.

Good luck.

[jmbour]

Hi,

Thanks to all. The play comes mainly from the progressive linkage lever and the roller.
I will replace them and adjust the linkage rod and hope it will solve the problem.
Anyway, I don't need full throttle all the time.4000- 4500 t/mn is enough.

JMB