300TD: No power when cold, fine when warm
 

(My first posting; hello everyone!)

The details: 1985 300TD Turbo
Cool Weather in Michigan (35 degrees F)
Car starts immeditately, BUT:
No power: full throttle barely creates movement
Once 1500 RPM's arrives: ROCKETSHIP acceleration
After 3-5 minutes, problem is gone, drives normally.

This problem is not affected by EGR disabling/reconnecting as tested during the last month. Once the car is warm, it drives it like a gas car. I have never fooled with the ALDA, but perhaps a past owner did--I have only driven one winter in Texas, so cold weather has not been a problem before.

Is this as simple as a vacuum line seal someplace? Where?

I have the same issue... I am thinking that it is a lack of fuel, from the lift pump... or lack of pressure. Not sure yet, but it is a lack of fuel in some respect.
Jason

Low power when cold
 

Your problem is caused by cold precombustion chambers. My SDL is also sluggish until it reaches operating temperature. I'm easy on it until it's warm because the transmission seems a little unhappy when it's cold. I'm not complaining... it's a high mileage powertrain that is still providing faithful service. :cool: It drive gently until it reaches 80°C and then I give it a good run through 3rd gear. After that, it's ready for just about anything.

An ALDA tweak will probably help you out a little bit. But keep in mind that the problem is inherent in the design of these engines. Remember, a diesel engine will make more power as it gets hotter.

cold chambers related to rpm level?
 

Why would it produce full power once the thing finally reaches 1500 rpms though? It is still cold but taking off like a rocket.

All MB diesels are sluggish cold -- my 300D grumbles and lags badly for the first half mile or so, and this is normal -- the precambers are stone cold, compression pressure is fairly low becuase you have excess clearances, etc. Once it warms up a bit (a mile or so), it's pretty much normal.

You get much better performance above 1500 rpm because the timing advances and you have some (if not full) boost and more fuel.

A minute or so of idling will help quite a bit, and drive very gently it at all possible while it warms up. Many a Volvo TD has been ruined by hard driving cold -- the timing and fuel delivery are both advanced to give more power cold, with the result that ring and cylinder damage can occur. MB doesn't do that, so you get to live with sluggish cars.

Small price to pay for the reliability and longevity in my opinion.

You should, however, check timing chain stretch and injection timing. Late timing will make this MUCH worse.

Peter

Perhaps all turbos are sluggish when cold as my 240D was fine in the cold.

Or maybe it was just hard to distinguish between too-cold-sluggish and typical-240D-sluggish? ;) :D

My 220D clattered like crazy and was sluggish until warmed up -- chain was stretched about 12 degrees, hasn't run since then.

All diesels are a bit cranky until the combustion chamber warms up. they smoke a lot more cold, too.

Peter

I can't accept the notion that these cars are all but unable to move when cold. Are you all saying that if you were to start your car, and once the oil pressure stabalizes, If you were to open the throttle to wide open, it is normal that the car will BARELY move. (like immagine running out of fuel, and trying to push your car, that is how fast my TD moves when it is cold.) In fact the motor will not turn over 1000 rpm for the first 30 seconds...

My Dodge will move along just fine, I dont push it, but then again I dont feel like I will have to get out and push to get it moving.

I think it is a fuel pump issue of some type, not much fuel=not much power.

Just my thinking, will replace my fuel pump this week with the one off the parts car just to see..

Jason

yup. i think an old car with compression that is not like new will be sluggish untill a little warmer. I f i start my car ('80 tdt) it is sluggish at first with a wide open throttle then takes off after it gets going ( i dont have an RPM guage) but after about a minute it works just fine. This has been my experience with all old diesel i ahve driven. we had a bunch of them at the pump company i usde to work at. we would always go out and start them up about a 30-45 minutes befor we left, if we had to move them around the yard they wer sluggish. My car even spits out wet exaust untill it gets hot, then its free and clear anddoesnt smoke at all. go figure. :confused:

Neither of our SD's started up on a cold day (35 out or less) will have much power to move, I've even tried it, I started it, put it in gear about 10 seconds later, and hit the gas to the floor, absolutely nothing :D It did roll a little, and kept rolling, then eventually the turbo came in and it got moving better. It will however, rev up (I don't do this ever, its bad for it) when cold and not in gear. After being on not more than 15 seconds it will easily rev to 1500-2000rpm no problem, higher if I allowed it too, but I don't. But its usually sluggish for me for 1.5-2 miles depending how long I let it warm up. If I give it 2-3 mins of a low idle warmup (like 1200rpm or so) it helps greatly. We tried to get our 83 up on ramps before right after starting it cold, it made it half way up, sat there growling (pedal too floor) and then rolled back down. Had to let it run about 2-3 mins before it had enough to get up the ramps. :D

Did you change the engine on your wagon?

When I got my 85 300TD-T about a month and a half ago, it too was VERY sluggish when cold, it would barely move off the line (though I can't honestly say any rocketship ever arrived). After lots of normal maintainence type stuff (valve adjustment, diesel purge, full fluid changes) it's still sluggish when cold, but it can at least get out of its own way.

If you haven't already, do the full maintainence routine. Just my 2 cents.

its from an '82 .I did not change it. i bought from a mercedes only shop in hollywood that did the switch/rebuild and sold it on lein because the customer did not want to pay, i got it for price of parts no labor and a free new rebuilt transmission only ,$2000 :D

All of my MB diesels were/are sluggish when cold. PSFRED mentioned that late timing makes this problem worse, and I agree. However, we shouldn't forget that this low centane fuel we're getting is a long shot from what these cars need, and may be contributing to the sluggishness.

I have noticed that if I boost the centane about 4 numbers (from 42 to about 46), the sluggish time period is greatly reduced. So you might add a little power service if you haven't tried that. Checking the IP timing would also be a good thing if you haven't done it in a long while.

Joe