Another Cold Start Issue ('82 300SD)
 

I've been having an issue starting the '82 SD. Get in, wait about 10-15 seconds after the glow light goes off, the car fires right up, no problems. However, to keep it running I have to rest my foot on the accelerator. If not, the idle slowly goes down and the engine stops. I cannot simply start the car and not touch the accelerator. The car will fire up in single digit temps, but will not stay running on its own when it falls into the 40's. After a few minutes of my foot on the accelerator, one of two things happens: 1. The idle goes up to about 900 rpm and stays there, or 2. the idle will surge up and down between 1000- 700 rpm.

A few things:

1. I use Mobil Delvac oil
2. I do not know when glow plugs were replaced, however, it starts right up, its the idle I have problems with...
3. It is due for a valve adjustment (to be performed this week)
4. I do not have a block heater installed (CA car)

The part that is so puzzling is that the '85 SD (with 140K more miles on it) starts right up and stays running...:confused: Any help is appreciated, also the car is currently at 220K miles, if that helps at all. Thanks, David.

You probably have the block heater installed. Just no cord attached to it. It is my understanding that almost all MB diesels in that era came with a factory installed block heater without a cord attached. It was then up to the new owner to bring it back to the dealer for a free cord install. I have the original book showing that this was done with my 84SD which was orginally bought in CA.

I would look under the turbo and above the starter. You probably have one and just need to attach a cord to it.

You shouldn't need to plug in a block heater with temps only in the 40's. I believe you are on the right track with a current valve adjustment. The surging is what puzzles me a bit. When was the last main fuel filter change? (spin-on) Possibly water in the fuel? When you do the filter change, dump the old fuel from the previous filter into a see-through jar, let it set for 24 hrs. and look for separation. If the result appears as two layers, then there might be water condensation in the fuel. How much volume of water (ratio to fuel) will determine the next action to take.

I have replaced the spin on fuel filter and the pre-filter within the last 10K miles. The tank filter has also been replaced recently. The surging gets me too, there is no rhyme or reason, sometimes it doesn't do it, this morning it did.:confused: I agree on the block heater, although I'll probably look into it, I don't think it would solve this problem as the car will start in the single digit temps, it just doesn't want to stay running at first. Btw, I am replacing the spin on filter and pre-filter this week as well, thanks for the input, David.

Yes, I agree a heater cord won't fix the problem you stated. I was just informing you that you most likely have one, just no cord attached to it.

I replaced the engine in my SD about 4 months ago. Mine surges as well. It surged in the warmer months and it surges in the colder months. It has new filters, valves adjusted to spec, syn oil. I have not done any tinkering with idle adjustments or such. So my surging is not due to clogged filters/air.

These issues point to lack of control by the governor flyweights. It's nothing that you can fix yourself.

BTW, the issue under #2 is called "hunting". It can occur when the temperature is very cold (0F or less) but is usually not all that annoying and clears up after the engine warms.

Thank you for the info, I didn't know that, I will definitely have that done regardless, no harm in having it warm when I get in!:)

Do you feel like I am stuck with this issue, or is there a repair that could be performed? Thanks for any info, I'm really stumped here...:)

My car hunts like that also, but only when the engine is partially warmed up, around 60c on the guage.

It has not tried to die after taking my foot off the accelerator after changing the oil from Rotella T to Rotella T "Synthetic".

You'd need to remove the IP and deliver it to a certified shop...........it's not inexpensive.

Also, 5 new Bosch glow plugs.

If you don't know when the last valve adjustment was, you should do it anyways. Your surging sounds a bit different than mine. Mine is like a RPM up and down surge that surges up for a second than drops for a second then surges for a second. I can't tell you what RPMS becuase my tach has been inoperatble since I installed an 83 tranny in my 84.

I recently had this corrected on my vehicle. It would stall in cooler weather (40 degrees) unless I lightly pressed the accelerator (only first thing in the morning). The diagnosis was an old/faulty fuel dampener regulator screw on the IP.

The repair cost me about $260 at an indy shop. Roughly $100 in parts...They also were able to adjust the fuel/air mixture at the same time for better running performance in cooler temps. My mechanic said that it may need to be adjusted when the weather heats up again, but not definite.

Since the repair the car runs much much stronger and I've got better fuel economy...

With regard to the former, I'll give the mechanic the benefit of the doubt and ask the question as to exactly where he found this "fuel dampener regulator screw"??

With regard to the latter...........I can absolutely tell you that this is not a factual statement. The mechanic cannot adjust the fuel/air mixture on a diesel. A diesel runs with unlimited air at all times other than full power. At that point it runs with just enough air.

How do you adjust air/fuel mixture on an OM 616/617?

I can see adjusting the IP timing...

My SD did the same thing in cold weather until I adjusted the valves.

I believe its aka a rack dampener screw. This screw is what was adjusted for cold weather idle.

What does the rack dampener screw "adjust"? I assumed it was the amount of fuel, is this incorrect? I'm curious.

The rack damper limits the motion of the fuel rack, and is spring loaded. It acts kind of like a shock absorber.

Where can you get a heater cord if you don't have one???

Call Phil with All Parts Express here at the website.

Here you go!
http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1982%40%401982&makeid=63%40%40MERCEDES%2DBENZ%40%4063%40%40MERCEDES%2DBE NZ%40%40X&modelid=6190%40%40300D&keyword=block+heater&subcatid=P:242394@@Block+Heater+Cord&mode=PA

I am assuming it is for your 82 300D.

I would not blindly assume that an '82 300SD came with a block heater. The 300D of that era, which also used the 617 engine, did not come from the factory with a block heater. The dealer would install one for free if you asked during the first year after new purchase but you were on your own after that.

Perhaps the S-class cars came with a block heater because they were the top of the line? I would check first. The block heater is on the right side of the block, down low and just ahead of the starter. If the block heater was installed but never used, it could have a plastic cap screwed on top of it and will be hard to see after 25+ years. If not, there will be a plug in the hole. Given the difficulty of removing that plug, I would vote for installation of a heater in the lower radiator hose.

Jeremy

the block heaters did not appear to be standard until M.Y. 86, from what I have read.
my 84 does not have one.

last I checked, the heater cord that was listed on fastlane was for a zerostart heater, not the original MB cord. so call before ordering.

I 100% agree. I was assuming he already verified he had a block heater since the only question he asked was where to find a cord.

I also agree that if it turns out he does not have a block heater then it would be easier to do a lower radiator hose install.

Update, after the valve adjustment I have no more issues.:D Every valve required adjustment, measurement tool would not fit! Car idles much smoother now. BTW, checked for block heater....negative, unfortunately there is simply a large bolt where the heater should be, no worries, it starts right up and actually stays running now! Thanks for all the input!:)

I have no doubt about this.

However, please determine if the problem with hunting has been eliminated via the valve adjustment. I'd have difficulty in believing this.

Since the valve adjustment was quite off, repeat it again in about 2 months. Afterwards, you will be surprised at how smooth it will purr at idle.

Sorry, I should have been more clear, the hunting is still present. However, when the car would do this before, as the RPM's lowered, it would stall out, and generally had a rough idle. While the car does still intermittently vary in idle speed, it does keep idling!!! The hunting doesn't really bother me, as long as I can run back in the house and wait for the car to warm up when its 5 degrees outside!!! Thanks again!