Gas Pedal no Revs ?

[alpina]

Today’s odd problem. Any ideas welcome. Driving up an off ramp from a motorway, I come to stop at a
Give way junction. I press on the gas pedal as normal to move off, nothing happens. RPM do not rise, no acceleration,
When pressing the pedal. Car is just at idle. Managed to pull over just with the engine at idle speed.

My initial though was a linkage rod had come off. First I bent down just to check the pedal. I Pressed it hard
A couple of time with my hand. What do you know, it starts revving as is if nothing had happened.
So put it in gear (4 Speed Manual) and carried on my journey home.

So who has any ideas what would have caused this?
Additional info if needed. This all happened after a drive of about 240km. The last 20km at highway speed
110 – 120km/h with a few higher speed bursts. The fuel tank was about ¼ full. This is probably the lowest
I have let the tank get.
Not sure if it would be a fuel problem, as the car did not die, I just idled normally. When turned off. It restarted
Without problem.

[cfm65@me.com]

Hi Apinaltd,
It sounds very strange. Confirm it only happened once and when you pressed it by hand it was fine?
Regards
Chris
Cape Town

[alpina]

Yes i only happen once. after it happened drove a further 10km filled with fuel and then a further 7km home. with no problem.
could something get caught up somewhere? thinking about it the pedal did feel different in some way. All very odd.

[Tyler S]

Double check the pedal adjustment jamb nut on the firewall crossrod and maks sure its not loose. Also make sure the l shaped linkage pivot under the manifolds on the block hasn't lost its "e" clip.

[alpina]

So after checking the linkages I made two discoveries. The first was, the vertical rod that comes up through the manifold, the top ball socket was loose. So as the rod moved up, it would turn in the thread of the ball socket. 
Not sure if this had anything to do with the problem or not, but it can't be good.
With this cleaned, lubricated and tightened, It feels a lot better pressing the accelerator, more responsive with a lighter touch, may even idle a bit better...

The second discovery was that the stop screw on the throttle body was backed all the way out. I have now adjusted this as detailed in the linkage tour.
Went for a test drive 120km the problem did not show up.

Could it be as the stop screw was backed all the way out. The Venturi flap/butterfly valve was able to
Bind in the throttle body causing my problem?

[Cees Klumper]

I don't think either issue could have caused the problem you experienced. The flap binding could have prevented you from being able to depress the gas pedal, bit since you were able to press it down it doesn't seem to be the explanation.

[TheEngineer]

Is it perhaps that the gas pedal moved sideways a little and therefore not engaged the linkage arm that comes down from the firewall? And when you moved the gas pedal by hand you centered it inadvertently and it engaged properly? Access is a little difficult, but check the gas pedal for sideways movement. There is a pin on the linkage arm that travels in a slot on the pedal to prevent such a thing.

[TheEngineer]

I just removed part of the throttle linkage from my car - the horizontal shaft that runs along the firewall. The gas pedal moves a vertical arm which is fastened to this horizontal shaft by a hex head bolt. There is also a tension spring opposing the push on the gas pedal. If the hex head bolt is loose the motion of the gas pedal would not transmit to the horizontal shaft. That may feel like no response from the gas pedal being depressed. (Credit for this insight belongs to Dan Caron aka Dr. Benz)

[ja17]

Sounds like the combination of the two problems you found could be the cause. If your car has a deceleration solenoid on the injection pump, this could also have caused the problem in conjunction with your linkage problems.

[Benz Dr.]

You can most certainly can have the throttle valve bind in the housing! Something you should know is to always make your throttle linkage adjustments on a cold engine. Those heated throttle valve housings on 280SL's expand a lot at 180 degrees and if you close the valve until it binds in a hot housing, well guess what happens once it cools off?

[alpina]

Thanks for all the suggestions. I have checked and adjusted all the linkages. Screwed in the stop screw so the butterfly does not bind.
Checked and adjusted the pedal joint at the firewall.
The problem has not shown up again.  (120km + driven.) The weather here has taken a turn for the worse. When the Sun returns I will test
drive again. Fingers crossed all will be okay.

Joe, I no longer have the deceleration solenoid on the injection pump, this was removed about a year ago
On the advice of Gus at Pacific Fuel Injection, as it was not really needed.