1996 E300D Smoking at precise Temp - PeachParts Mercedes-Benz Forum

jfulford · #1 02-02-2014, 04:55 PM

I've been working on this issue for about 6 months. What happens:
In the morning, on the way to work, at about or right at 60-65C, I will get a lot of white and gray smoke out of the tail pipe, and the car feels as though it is getting "over fueled", ie, picks up speed a bit.

I have changed the EGR, cleaned the intake and head ports(as much as i could), checked the "flappers", all 3 of them, for good vacuum and functionality, ran Diesel Purge through the system, and finally bypassed the EGR. None of this has stopped the smoking/overfueling.

Here are my ways around the issue: Plug it in overnight(block heater).
This seems to *always* stop the smoking. It seems it is a temperature related issue, but what is turning on or off around 65C?

Another Data point: While idling the car, I watch the temp gauge go up slowly, so I went ahead and idled up the engine to 2K for about a minute.
At the appropriate temperature, the engine "took off", ie, went to 6K for about 5 seconds, I shut off the car, and it continued for another 3 or 4 seconds.
It also left a nice "carbon" smudge on the street.

The car has 258K on it and, other than this, it runs perfectly fine, starts very quickly.
Any ideas out there?
Jeff
jfulford1@earthlink.net

sixto · #2 02-02-2014, 05:06 PM

Maybe a temp sensor has become non-linear. Does it have OBDII so you can monitor temp sensors with easily available equipment? Depending on the cost, a new EDS coolant temp sensor and air intake temp sensor might cost less than further diagnosis. The air intake temp sensor might be something you can clean.

Sixto
87 300D

jfulford · #3 02-02-2014, 06:07 PM

Quote:

Originally Posted by sixto

Maybe a temp sensor has become non-linear. Does it have OBDII so you can monitor temp sensors with easily available equipment? Depending on the cost, a new EDS coolant temp sensor and air intake temp sensor might cost less than further diagnosis. The air intake temp sensor might be something you can clean.

Sixto
87 300D

Thanks for the response. It does have obdII; I have monitored the temperatures(coolant). The only other temp sensor is the air intake sensor. I will watch this; I think it can be monitored.
jeff

sixto · #4 02-02-2014, 06:33 PM

I suppose the thermostat can be hanging between fully closed and fully open, or fully opening too soon. Maybe you can compare OBD temperature profiles with Jeremy/jeremy5848 since he's a budding 606 whisperer

to find the non-linearity.

Sixto
87 300D

jfulford · #5 02-03-2014, 04:44 PM

I've been hovering around the "Differential Pressure Valve" as Mercedes calls it: 6060100091. I've replaced all of the ancient hardened breather hose pieces to clean up oil smudging and cleaned this valve. I keep thinking that, maybe, the oil is coming all at once from this valve that is sticking UNLESS I let the block warm with the heater. Then it continually allows whatever blowby there is to be burned a little at a time. Still not sure. Haven't owned the car during the summer to verify this yet.
jeff

RunningTooHot · #6 02-03-2014, 05:55 PM

Sorry guys, but I think you're barking up the wrong tree.

I don't see how the breather valve could possibly have anything to do with it.

And as far as the fuel thermostat, I have had some (unconfirmed) suspicions in the past regarding it (potentially) causing temporary fuel starvation at the switchover temperature. It is not, however, going to suddenly force the injection pump to start injecting a bunch of extra fuel.

I'm not familiar with the early NA 606's in the w210's - but if it has an electrically controlled injection pump rack, then I would look towards the control systems for that going out of whack at a specific temperature. What could cause that? IDK. Start giving the temperature sensors & computer the evil eye.

Lucky you didn't end up with a giant ventilation hole in your block when the engine ran away. Another testament towards the almighty om606.

jfulford · #7 02-04-2014, 10:45 AM

Thanks for the reply. Yep, I was waiting for a rod outside of it's natural habitat!

I think the 96 is still a mechanical pump. Looks just like my 86 190D with the same fuel pump on the side(at least looks like the same one).

May start replacing sensors as I find them(or at least cleaning them.

I now have repeatable results in 2 different ways. I would think there would be something on this "smoke turn on" temp thing. It is just too predictable.

I just keep plugging it in and I never see the smoke. Forget to plug it in and get smoke around 60C( or so) or 155F (or so). EVERY TIME! The car runs and drives very smooth, idles very smooth. No major leaks. No drive-ability issues. Mileage around 28-30 mixed(mostly highway). All filters have been replaced. All flaps good. EGR bypassed until I can get this figured out.

Jeff

RunningTooHot · #8 02-04-2014, 11:46 AM

The pumps themselves are still "mechanical", even on the fly-by-wire cars, it's just how they are controlled that is different.

If your accelerator pedal cable actuates (via linkage) the pump directly, then the fueling is not computer regulated. If the cable ends at what is probably a large potentiometer (not physically connected to the pump) then it is computer controlled.

GregMN · #9 02-04-2014, 04:56 PM

Quote:

Originally Posted by jfulford

I think the 96 is still a mechanical pump. Looks just like my 86 190D with the same fuel pump on the side(at least looks like the same one).

The pump is mechanical, the throttle is by wire. At 60C your fuel control module is getting a signal to go full throttle.

If you let it idle from below the trigger temp. to above it, does it misbehave? or only when the foot throttle is depressed ?

Fuel control module (they call it a diesel shut off valve) : Pelican Parts - Product Information: 000-078-44-49-M14

Coolant Temp sensors (needs 2) : Pelican Parts - Product Information: 011-542-51-17-M85

GregMN · #10 02-05-2014, 09:57 AM

There are 2 coolant temp. sensors. Find them.
Unplug one of them. See if the problem still exists.
If so, unplug the other one the next morning.
Once you know which circuit is causing the problem, you can begin to trace it down.

jfulford · #11 02-05-2014, 10:24 AM

GregMN,
I have never tested it from just idle to all the way up to the point(60C). I came close but brought it up to 2000 for about a minute before it did it's "overfueling" trick. I'm not a 100% sure but I think it is regular oil that is doing the overfueling. I could be wrong.
I found both of the cooling temp sensors on the parts sheets and had previously looked up the Shutoff/Fuel control module.
This weekend I will try the "only idle" running and see if it will go.

Thanks
jeff

GregMN · #12 02-05-2014, 11:14 AM

Quote:

Originally Posted by jfulford

...I think it is regular oil that is doing the overfueling. I could be wrong.

How is the crankcase oil getting into the intake ? and why only at 60C ?
I don't think it is crankcase oil. If it was, shutting off the key would have had no effect when you had your "run away" condition.

I can only think of one interface between the crankcase and the intake, that is the crankcase ventilation system. But I do not think that is temp. sensitive in any way.

jfulford · #13 02-05-2014, 01:10 PM

GregMN,
I know what you mean. It is frustrating as hell. However, during the "non-moving" episode, when I shut off the key, it did keep going for another 2 or 3 seconds before shutting off. I suppose it could be leftover diesel, and the smoke I am seeing(GRAYISH) could be leftover diesel. My oil level is going down(probably about a 1000miles a quart) but, as mentioned, no other smoke, cold or hot, when driving Except the previously mentioned scenario.
How could you get a short term "oil" injection event? This is why I keep circling around this. I will try the "cold idle up" with my OBDII reader on it.

jeff

RunningTooHot · #14 02-05-2014, 02:16 PM

Quote:

Originally Posted by jfulford

GregMN,

This weekend I will try the "only idle" running and see if it will go.
jeff

May I suggest that if you decide to 'idle test' it, you keep it in gear with your foot firmly planted on the brakes while doing so. This will allow your transmission to absorb energy and prevent the engine from over-reving again IF it acts up. (Obviously you only want to do that at idle, not purposely loading the trans by manually holding the rev's up - duh!)

jfulford · #15 02-05-2014, 03:37 PM

Idle test: Good Idea. Better than a 6K run-away! I have some experience in this, except not the good kind: 69 350 Chevy, in gear, course I'm revving it and messing with the brake pedal till I get the rear tires to break loose!

I may try this when I get home. Drove the Ram Cummins today(CP3 pump).

jeff