What does rack dumper actually do? - PeachParts Mercedes-Benz Forum

xxx_st · #1 07-18-2007, 02:54 PM

Could someone please explain me what does rack dumper do, cause i dont like doing something that i don't understand, i'v ordered golden rack dumper to change old silver one on my 300 sd

oilslick · #2 07-18-2007, 05:42 PM

I don't know what a "rack dumper" does. You might want to search for the function of a RACK DAMPNER

Kevin

Parrot of Doom · #3 07-18-2007, 07:53 PM

Over in the UK a rack dumper is probably something certain perverted people might pay a lot of money for.

#4 07-18-2007, 09:08 PM

The rack damper does exactly that, dampens the rack.

The firing order is 1-2-4-5-3 (front to back slowly and back to front quickly) so the engine naturally wants to rock back-n-forth. The rack damper reduces that oscillation.

lietuviai · #5 07-18-2007, 11:07 PM

I've seen one with a bad rack damper. The engine rocked back and forth badly like an overloaded wash machine.

SD Blue · #6 07-18-2007, 11:54 PM

The IP uses a rod to vary cams for each piston that changes the amount of fuel delivered......this rod is called the "fuel rack". When the rack drops back to minimum fuel, the engine is on the edge of shut off and causes the rocking motion. The rack dampner eases the last portion of travel of the fuel rack to gradually lessen the fuel to idle.

#7 07-19-2007, 12:02 AM

OK, I'll try to give you a straight answer. The rack damper is a spring loaded device that presses against the "rack" inside the injection pump at idle speed. Because this rack would have a tendency to "hunt" back and forth while trying to maintain a constant idle speed (resulting in a rough idle), this device dampens the movement and smoothes out the idle. You adjust it by screwing it in or out, the further you turn it in the more damping you will get. Too much damping can result in hard starting or stalling, too little damping can result in a rough idle. You can adjust it by unscrewing it until the idle begins to get rough, then screw it back in until it smoothes out. Eventually the spring inside the damper will get weak and it will need to be replaced. The original dampers were silver in color, and the "new improved" dampers are gold in color.

I assume you know were it is located?

#8 07-19-2007, 12:04 AM

Quote:

Originally Posted by SD Blue

The IP uses a rod to vary cams for each piston that changes the amount of fuel delivered......this rod is called the "fuel rack". When the rack drops back to minimum fuel, the engine is on the edge of shut off and causes the rocking motion. The rack dampner eases the last portion of travel of the fuel rack to gradually lessen the fuel to idle.

Sorry, we posted at the same time. Good explanation.

xxx_st · #9 07-19-2007, 05:31 AM

Thanks guys, now i understand it, mine 300 sd has some 380000 under it and still running like new, this old lady is great car it has been in my family since 1985.