So, this car has unknown high mileage (at least 400k, but maybe a lot more). It seemed to have been well maintained when I got it, and I have driven it daily and changed the oil, fuel filters, transmission fluid, etc but thats about it.

Recently I noticed it was idling (slightly) higher than normal when idling in gear. With a little investigation I found that if with it in park or neutral if you rev it to ~2k rpm, the engine will continue to rev higher and higher until you shut it off even though the throttle linkage is closed.

Also, if you accelerate from a stop to ~50 mph then take your foot off the accelerator, it will continue at that speed with no pressure on the accelerator, then once you apply the brakes it will slow down and idle in gear a bit higher than what is normal.

I do not want to drive it again until I figure out what is going on, especially since it has had an intermittent problem with not shutting off with the key since I got it, and sometimes is even difficult to shut off with the stop lever.

My feeling is that something in the injection pump failed, if that is the case it will be for sale, I dont have the skill or money to replace it, but it would be a decent car for someone who could.

Is ti burning oil? Sounds like the Turbo may have an oil leak. Then the oil gets fed back into the intake creating a feedback loop that will runt he engine away as it burns it's lubricating oil as fuel.

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1978 Mercedes 240D
1981 Mercedes 240D
1982 Mercedes 240D

It doesnt seem to be using oil at all, I will pull the intake hose and take a look at the turbo though.

Have you lubricated the throttle linkages lately and throughly? This can happen if the linkages are dry. Coincidentally, it was a recurring problem on an '83 300sd that I owned, the only turbodiesel I have had that issue with.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I just went out and checked the turbo, it has pretty much no shaft play, and there is a slight amount of oil in the intake but I dont think that its enough to cause it to run off the oil like that. I lubricated the linkage in the last year, and I did check and see if it was binding anywhere or if anything was loose and it doesnt look like it. If the rpms keep climbing with the accelerator pedal in the position where it would idle normally and the linkage doesnt have a massive amount of play would that rule out the linkage? It seems like it would.

In your reply you say:

In your original post you said:

I want to be sure you are talking about the same thing.

If you are saying that the car also starts to run away while sitting at normal idle speed, that is extremely serious. If you are saying what you said in the first post, that is exactly what my car did.

At idle (no load) it takes very little additional fuel to get these motors turning fast. I am not sure if you would necessarily be able to tell there was a difference at the pedal, I don't remember if that was the case on my '83. How the linkages feel isn't necessarily relevant, unless you have another car beside you to compare.

I would suggest you give the linkages a good lube then see if the problem recurs.

I would also suggest you ask someone else with an '83 to post a pic of the linkage setup (I don't know if it's exactly the same on all years of 300sd, w126). It IS possible to take the linkages apart and reassemble them incorrectly (wrong length of linkage in wrong place). The result is that the car operates, but the linkage may be 'pulling' slightly when at rest -- or other things.

When I had the motor replaced by a shop on that car, the shop did precisely that. The car didn't run away, but it did something worse, if you pressed the pedal too far down the linkage would snap to full open. Luckily this was caught and fixed with the key in the OFF position....

Overall, however, I would look at the injection pump as the last possible cause.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I seem to recall there is a spring on the throttle shaft from the firewall... I'll look later today.
also, the carpet pads tend to bunch up on the accelerator, check that.
I've also had issues with the heater hose that curls around the oil filter, being moved for the oil change, and not put back, so the linkage binds on the hose...

I totally agree, that unless you have just lubed the linkages, you need to lube them now.
all of them.
from the ball on the bottom of the IP shaft, to the cruise actuator, to the vcv valve on the valve cover, and all the pivots etc...

__________________
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 read his account differently. At idle, he revs it to 2000 rpm. Then the linkage returns to idle, but the engine continues to increase in rpms. That's not a linkage problem.

I would reach behind the IP and make sure the linkage is pushed back to the idle position and confirm that the rpm's increase anyway. At that point, its either a problem internal to the IP or its getting fuel from somewhere else.

__________________
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

Kerry is right and it may take two people to examine the situation while active. Almost impossible for one person really sometimes. It is not the positon of the pedal as much as where and what is the arm on the injection pump doing during the event. If staying at the beginning of its movement range and revs are starting to build then it has to do with faulty internals of the injection pump.

Even if it turned out to be an injection pump one from a pick and pull should not be much.

Yes, that is the best description of what happened. I only discovered this after noticing the high idle speed and the other issues I mentioned. It will actually be easy to check with the engine off, because I can reach down and pull the accelerator pedal all the way up with my hand and the RPMs still keep climbing. I will just try (without starting it) having someone press the pedal to the floor and pull it back up, and if the linkage closes all the way then it's probably not that.
If the injection pump has failed I'm going to have to sell it, hopefully someone will want it who could fix it, it's in nicer shape than most of them that are left, so I really don't want to part it out or sell it to pick and pull.

Why would you sell it if the IP is bad?

__________________
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

[QUOTE=

If you are saying that the car also starts to run away while sitting at normal idle speed, that is extremely serious. If you are saying what you said in the first post, that is exactly what my car .[/QUOTE]
It will start to run away when it should be at idle, but only if you rev it up first. If you just drive normally then brake and shift to park, it will idle at 1000 rpm or so and stay there though. I'm concerned about driving it any more because I would rather sell it to someone who wants to fix it than blow the engine because it ran away and I didn't have a way to stop it fast enough.

If someone has not already said this pop the Linkage off of the Throttle Arm on the Fuel Injection Pump. If that Solves the Problem you have an issue with the Linkages.

If it still does the same thing try backing out the Rack Dampner/Governor Idle Screw. I think I have read of it creating the symptoms you speak of when it is screwed in to far.

On My W123 there is a Throttle Retun Spring that attaches to the Fuel Injection Pump Throttle Arm on one end and the Rear Bracket under the Fuel Injection Pump on the other end.

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84 300D, 82 Volvo 244Gl Diesel

One thing I forgot to mention is one of the adjustment screws is snapped off the back of the pump, it was like that when I got it (I didnt notice it until a few months later though). Other than occasionally running rough it has ran fine until recently. Is there any place with information about the adjustments on the pump? I really know nothing about it at all.
I think I am most likely done with diesel ownership after this though, I will look a little more to make sure its nothing easy, but otherwise I will clean it up and post it for sale next weekend. Hopefully someone will want it, it still looks nice and only needs a few other things fixed to be a nice car.

That is an important detail. What is snapped off is the idle adjustment screw. That is the only adjustment on the back of the pump that I can remember.

Based on my experience: when that snaps off (which happened on my '83), the linkage doesn't stop at its correct rest/idle position -- the result is that the car will idle very, very low, so low it will likely stall when put in gear with the motor hot.

I am guessing that someone has monkeyed the linkage, somehow, to make the car idle more normally. You are most likely seeing the side effects of whatever was done.

I managed to 'fix' mine by using a big, HD zip tie that held the linkage from moving much past its old rest point. I thought that was an ok fix, worked fine for six months....

I later lost that engine to the linkage locking up while I was at full throttle (what I call a runaway). In a huge rainstorm. I also nearly had to drive off the road to avoid causing a major collision before the car slowed down (an OM617 can overcome the car's brakes, once you are moving at a decent clip, before it spins down once the key is off). It was one of the most frightening experiences behind the wheel of my life.

Voice of experience: I think it would be a good ideal to avoid driving this car until you walk through the entire linkage setup with some of the veterans on this board and/or Roy Hunter, by posting photos, or you have someone who KNOWS these cars at a local shop look at it.

__________________


Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22