300SD Won't idle when cold - PeachParts Mercedes-Benz Forum

JBC · #1 10-31-2005, 02:43 PM

I have an 83 300SD with 163k on the odometer. The problem I have is the engine won't idle after startup. It takes about 2-3 minutes with my foot on the accelerator before it will idle by itself. Also, I have to press the accelerator down about half-way before the engine will start. When I do depress the pedal, the engine starts up right away without any hesitation. When I don't , the engine cranks for about 10 seconds before it starts sputtering and then dies immediately.

Right now I have one bad glow plug, and I was considering buying the kit with 4 plugs and a new relay. I was hoping that the new relay burning the plugs for 3 minutes instead of 30 seconds would solve this problem. I was also considering increasing the idle speed.

My buddy has an 85, and he tells me that all he does in the morning is open the door and reach in and turn the key and the thing starts right up.

Does anybody have any experience with this?

gene2 · #2 10-31-2005, 06:08 PM

JBC, I have the same problem with my 1985 300CDT...will not idle until it warms up a little...in the summer, it starts and idles great... I do not think it is glow plug related....Please let us know if you find your problem, I will do the same......gene 2

vwbuge · #3 10-31-2005, 07:44 PM

I would bet that you have more than one bad glow plug.

pawoSD · #4 10-31-2005, 08:05 PM

I had the exact same problem, it turned out to be the rack damper pin being in too tight.

gene2 · #5 10-31-2005, 08:51 PM

Where is the rack damper pin located?

#6 10-31-2005, 08:52 PM

I have an 82 300sd and I have to cycle the glow plugs at least 3 times before it will start and idle fine. I am going to replace glow plugs soon and probably a block heater too.

Oh, what happens if the idle is too high or too low? also, what would cause the tranny to downshift hard?

ps, which glowplugs are best bosch or beru?
thanks -zach

#7 10-31-2005, 09:05 PM

Once the engine is started it should run on its own (the old style relay on the 617 shuts off after you stop the starter)

SO if it starts up..then dies...don't even bother with looking at the glow plugs yet. ALl they do is get your started...not keep you running.

I'd look at fuel supply and/or the rack dampner pin (although its odd that it would be too tight)

gene2 · #8 10-31-2005, 09:25 PM

Thanks Col. gene 2

JBC · #9 11-01-2005, 10:17 AM

What does the rack dampner pin do?

#10 11-01-2005, 12:45 PM

Quote:

Originally Posted by JBC

What does the rack dampner pin do?

Puts light pressure on the end of the rack linkage to keep it from building up harmonics with vibration at idle and make your car go "whup whup whup whup"

Adjusting it in too far can make your car idle too low and die. Too far out and it will not apply enough force.