PeachParts Mercedes-Benz Forum - WM Injection Pump and Idle

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WM Injection Pump and Idle

I'm hoping one of the IP experts can chime in and shed some light on this.

OM616 & WM IP
In short, is there an idle governor?

The long, idle set in park to 750-800 via the adjustment on the outside of the pump. Should idle not dip and then recover to the set point when a load is applied, like shifting into drive or when the A/C compressor kicks on?

I've been searching all week for info on both the mechanics of the pump and the governor assembly. I found a lot of great info on the actual workings of the WM pump but haven't found a single thing on the governor. If anyone could point me to some info on that I'd really appreciate it as I would really like to get a grasp on that portion of the pump.

Thanks!

There's quite a bit of information in the FSM. Chapter 07-010 - in the W123 FSM - have you seen that?

Quote:

Originally Posted by tee51397 (Post 2948522)

The Governor Idle Pin/Rack Dampener Pin is only on the Turbocharged 5 Cylinders with MW Fuel Injection Pumps.

There is indeed an idle Spring inside of the Governor and the as long as the Idle adjustment is with in the range of the Spring the Idle is controlled by the Governor.

If you adjust the idle to the extent that the Idle Spring is completely collapsed the Governor cannot control it and you go into the midrange area where there is no governor control. People have said that can cause a runaway when you step on the Pedal.

On models that have the Rack Damper Screw if the screw is run in to far it can have a similar effect

I did read everything on startekinfo about the pump. I guess I was looking for more detailed info on the specific mechanics. I found good info on the actual pump from Bosch manuals, much more detailed than the FSM and was hoping to find something similar on the governor.

Quote:

Originally Posted by tee51397 (Post 2948617)

Over on the superturbodiesel forum they have some pics of the inards of the Governor.

basically the internal idle screw needs to be turned in(clockwise) about a 1/4 turn or so, and the external one backed off a bit.Be sure to back off the external screw before starting the engine. The external screw has more of an effect on how quickly it returns to idle, and the internal screw will set a firmer idle, so a/c will not change the idle speed, or at least not much. Here is a real good document about m/w pump thoery

https://docs.google.com/document/d/1QkAv-HFaLqpK_5wKCln6DODkfw_DkjBHVYZXm0nUtEw/edit?hl=en_US&authkey=CJXuhs0I&pli=1

Quote:

Originally Posted by 47dodge (Post 2948800)

Perfect info, and supports what I suspected. Thank you! Interestingly, when manually upping the idle to compensate, I can also feel feedback through the throttle at WOT as the governor kicks the rack back. That link completely explained why. I can't wait to tear into things for some reverse-engineering, better understanding and experimenting.