Good day all, I recently purchased my second 300SD (1985), a parts car with a recent rebuilt motor. It has been sitting for plus or minus 2 years outside according to the elderly previous owner. She parked it due to a massive fuel line leak.

It was a bit cranky to get going, but I had it running with the leaking fuel line, trouble is that it starts then revs to what sounds like close to redline (dunno cause the tach is dead of course). This seems like a partial runaway, but is confusing because when I shut it down by the key, it shuts off quite readily. I cant see the linkage being stuck open.

I had a few thoughts on perhaps air in the fuel might make it rev higher, I know when my ford 7.3 tank went dry it would rev up intermittently under it's own power just before it died, so I thought it might be something along those lines. I am also thinking there may be a leaky injector or two from sitting, but I am unsure how common that is. Last thought was sticky rings from sitting, but that should be uncontrolled runaway symptoms I figured and the engine shouldn't have that much wear on it.

The motor was rebuilt within 50000Km by the MB dealer, so it should be golden (total rebuild as the old owner ran it out of oil and seized it, some $12500 bill she showed me).

I haven't changed any fluids or oil yet, because I wanted to test it before I put money into anything. Maybe I should put new oil in her at the minimum for testing, any suggestions on how to calm it down so I can warm up the beast and give it a thorough run in?? I'm getting frustrated and don't want to blow it up quite yet..

Steve

What's the level of the engine oil? Is the exhaust smoky when it runs up to redline? In other words, is it burning engine oil or diesel fuel when it runs away?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

if it was burning engine oil, turning off the key would do nothing.
it has to be a fuel problem.
I would look over the linkage really well.
if a rod was off, you could get similar problems and the key would still shut it down.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I'll try again and double check the linkage, maybe I'll disconnect it and manually work the pump if necessary. Are you suggesting the rod linkage is also the pump return mechanism though?

The oil level is good, and there isn't any crazy smoke coming out the other end, other than what I would expect from an engine that hasn't started in two years anyhow.

Air in fuel? no one seems to think that might be an issue? The fuel filter looks good without too many bubbles in it or anything

Leaky injectors perhaps, any way to test for those without replacing them? I have no spare injectors kicking around...

Forget the oil level.........air in the fuel........leaky injectors.

The problem is due to a binding linkage. If the rack won't fully close, a diesel has a tendency to run away..........and it doesn't take much to let that happen. You'd never notice it in the position of the pedal.

Does it have the old primer pump? They ofter go bad and a leak in that can cause it your problem, and it is downstream of the first filter so you won't see the additional bubbles. Simple fix with the newer model primer pump: http://www.peachparts.com/Wikka/PrimerPump

(a piece of my own handy work by the way)

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Peach Parts W124.128 User Group.

80 280SL
85 300SD
87 300TD
92 300D 2.5 Turbo
92 300TE 4Matic

wallyj has the idea. Disconnect the linkage at the throttle lever. If it is still running away there is a problem with the IP rack sticking as Brian Carlton said.

Brian; is it possible that the IP Vacuum Shutoff has been installed wrong and would cause the engine to run away but still shut the engine off?

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84 300D, 82 Volvo 244Gl Diesel

Any chance that the idle screw is adjusted too much beyond idle?

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84 300D, 82 Volvo 244Gl Diesel

picture attached.







Have a great day

Attached Thumbnails

 

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1985 300SD
1983 300D
1984 190D
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I've got the issue solved, it was a frozen linkage..., boy it runs well, but off the line today it is a real dog, I don't think it is having any boost off idle. I'm going to look into some of the more common power loss issues like the ADLA circut, but I can't hear the turbo, so I am kind of wanting to verify the wastegate isn't messed up. Are the turbos really that quiet?

In case you haven't noticed I have jumped into the deep end of the pool with 2 Benz's in a row, so I am not that familiar with how much power they do or do not have.

I did notice some significant corrosion where the front sway bar passes through the body, I don't think the sway bar is that functional right now hahaha!! such is life with the old cars I guess..

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1981 300SD, 174000Miles
1982 300SD, 247000KM
1985 300SD, 318000KM and counting

Steve

Hello everyone, this is the first post that has actually helped diagnose the type of runaway I'm having instead of just telling me how to stop it.
Our 1979 300D slowly started to runaway a few weeks ago and yesterday was the first one that freaked me out. I had driven it about 8 mins down the road and put it in park and the engine revved extremely high over about 5-10 secs. I immediately got back in the car and shut it off with the key and it turned off just fine.
It also seems like the cruise control is stuck on when I'm going about 40 mph or greater but I can't feel the pedal moving at all. I know the cruise control isn't working however. I definitely do not have any binding of the throttle linkage as I went through everything again last night and then went on another test drive and had the same issue when I came back and put the car in neutral. There is only minimal smoke (even when it ran away) but the car does consume about 1 quart every 300-400 miles or so.
My wife and I replaced the shutoff valve in the IP about 6 months ago and it hasn't done anything like this until just recently. Could that be the culprit?
Thanks for any insight and keep the humor up so we don't all go crazy!!
Brandon and Megan Oswald
Pensacola, FL
1979 300D "Red'
1985 300D Turbo "Blue"

You might not have any "binding", but you probably have restricted travel of the linkage. You won't be able to tell this by operating the linkage.

Refer to post #9 of this thread and remove the socket from the ball as Roy shows in the picture.

You will now have a proper curb idle (and nothing more) if the IP is functioning properly. If it is, then the linkages to the pedal are too short at some point and not allowing the rack to fully close.

Please be aware that this is HEAVY oil loss.

* Check for external oil leaks, we need to know for diagnosis, (pictures are best).
* Overfilling is common, the engine takes eight quarts for oil change (ignore the dipstick).
Wrong application, damaged or defective dipstick is possible.
Find another owner near you, meet them, and borrow their dipstick for level comparison, (a few seconds is all you need it for).
Check engine oil level in the morning, BEFORE starting.
It takes hours for all of the oil to drain into the pan.
You are always safer running half quart low, than risking any overfill.

Reading this thread will cover almost every possible cause.

Run away diesel, why does it happen?
Run away diesel, why does it happen?

Thank you Whunter and All for previous advice. We have another problem that I believe we've mentioned before but may not have described accurately.
The 1979 300D has a normal idle speed while in park. Once shifted to drive the idle RPM's drop significantly and even more so if the A/C is on, to the point that when I press the gas pedal, the car will die. If the A/C is off, I press the gas pedal and the car does nothing (no increase in RPM) for 2-3 seconds until finally the engine picks up. If the car is rolling, the delay is less and when the engine does accelerate, it appears to be at a normal rate for this non-turbo engine.
We've adjusted the idle on the top of the throttle assembly as well as the nut/bolt at the bottom, near the injector pump. We've also used the manual adjuster on the inside of the car but it really doesn't make a difference if the car is completely stopped.

What about the air and fuel filters?

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

91 W124 300D Turbo replaced, Pressure W/G actuator installed. 210K

90 Dodge D250 5.9 Cummins/5 speed. 400K