Increase engine rpm OM421 (1222AF)

[Maurizio]

Hi all
I have a MB 1222AF that doesn't go over 2000 rpm and 75 km/h. I would like some help to understand how I can increase them a bit. Could there be a limiter?
thanks a lot to anyone who can help me.

[4x4V10]

Hey,
do you only have the problem (2000rpm - Not 75km/h of course) in last gear or in every gear?
Best
Constantin

[Maurizio]

Yes. Every gear only 2000 rpm

[w3llschmidt]

Astonishing. Can you check if you can bring them over 2000rpm by hand via the lever on the pump ... ?!

There is a RPM warner, yes ... but this triggers only a warning tone.

[Maurizio]

If I push the accelerator lever through the engine hood it reaches 2300 rpm.
On the pump there is a kind of piston that controls the lever

[felix]

Hi,

then disconnect the cylinder and test.

Regards
Felix

[w3llschmidt]

Do it here ...

[Maurizio]

I'll try, but the cylinder is pneumatic and I'd like to know what it controls or what it is controlled by

[Maurizio]

I also tried adjusting the throttle limit screw on the pump, but it didn't change

[4x4V10]

Even 2300rpm is Not enough for the OM421… should be around 2500 +|-.

Best
Constantin

[Maurizio]

Thank you very much
I will do some tests

[Pirx]

Maybe this old thread (concerning another problem) will be helpful:
viewtopic.php?p=1112059#p1112059

It shows the different pneumatik cylinders in the injection system of a OM421 engine.
Maybe one of them is the cause of your problem?

Pirx

[Maurizio]

Hello everyone and thank you very much for your help.
I solved it by adjusting the throttle connection under the hood.
Now it reaches 2500 rpm and almost 100 km/h

[Maurizio]

Maybe this old thread (concerning another problem) will be helpful:
viewtopic.php?p=1112059#p1112059

It shows the different pneumatik cylinders in the injection system of a OM421 engine.
Maybe one of them is the cause of your problem?

Pirx

Thank you so much for the link. This post is really interesting and helpful

[felix]

I'll try, but the cylinder is pneumatic and I'd like to know what it controls or what it is controlled by

Hi,

these cylinders were potentially used to implement the required speed limiter for trucks with mechanical governed injection pump.

Or the cylinder is used to switch off the injection when activating the engine brake.

MlG
Felix

[Maurizio]

I'll try, but the cylinder is pneumatic and I'd like to know what it controls or what it is controlled by

Hi,

these cylinders were potentially used to implement the required speed limiter for trucks with mechanical governed injection pump.

Or the cylinder is used to switch off the injection when activating the engine brake.

MlG
Felix

I tried to stop the engine from the cylinder near the pump and it worked fine. I have to study how the others work