300D - No power and hard shifting - PeachParts Mercedes-Benz Forum

300TD · #1 06-23-2006, 09:25 PM

My parents are going to give me theri 1983 300D for my 17 year old daughter to drive which I think is great. Overall, the car is in decent shape for a new driver. My concern is it's complete lack of power. It is dangerous in my opinion. First, It will get a valve adjustment. I do not know the last time that happened. After that I need to see if there is any change. The trans also shifts very hard first to second. This may be engine related and I will see once we get the power curve a little (alot) better.

I have done a search but maybe I am not using the correct combination of words to find what I need. Any help pointing me in the right direction would be a great help. I know the collective knowledge here is amazing.

Thanks for looking and I appreciate any help you all may have to offer.

Targa-NF · #2 06-23-2006, 09:31 PM

Check all the vac lines.It could be your boost protection valve. "Or BP Valve"
It is the little unit on the the firewall with vac lines going to the alda and the
intake manifold. My SD would not go up hills for @#$& !!! I took the BP valve
from my friends 300 CD and bang.... It was a whole different car. If you know
someone with the same turbo diesel engine, just switch it with yours. You
will tell right away if that is your problem. Also the BP valve on a 300 D or CD
looks a little different then the SD's, but it will work the same. Jay

81 300SD Black 132M "Sold"

81 300SD Blue 139M "Sold"

81 300SD Blue 246M
82 300SD White 202M
84 300SD Burgundy 168M "New"

85 300SD Gray 267M "New" "Has damage to the rear"

84 190D Red 111M "New"

miner · #3 06-23-2006, 11:50 PM

Those lines going to the alda through the switchover valve are pressure lines, not vacuum lines.

But that doesn't matter, what Targa-NF said is still correct. My boost line was cracked at the manifold. I fixed it but cant tell you it made a huge difference, but I am only able to drive this thing around the block for now as i am still waiting for registration.

On the other hand. Checking the vacuum connections and lines IS something I can tell you made a huge difference in the shift quality of my 300d. Some PO put a bb in the line to the transmission and that lead to no vacuum to the modulator. Fixing that gave smooth even shifts. If your vacuum pump is bad or if you have substantial leaks it can do the same thing I imagine.

Samuel M. Ross · #4 06-24-2006, 01:52 AM

but let me:
(1) Mileage - say that I wish you had given the mileage on this veteran car !?
(2) Valves - second let me concur that the valves adjustment is a good early bet for maintenance... especially since you do not know when they were last adjusted. In this regard, be certain you or whoever the mechanic is checks the timing marks to determine how much stretch there might be in the timing chain. Report this back on this THREAD.
(3) Tranny - As to the hard shifting, knowing the mileage is very important to know. Also please confirm whether this is a W123 or is it by chance a W126 chassis. I'm guessing W123, and if this is the case, you most likely have a tranny that might just benefit from an upgrade kit... but let's not get ahead of ourselves. It would be helpful if you could confirm precisely what 617 engine and what 722.??? tranny you have. In all likelihood your car uses what I would affectionately consider a god-awful vacuum control system, one that even many good and experienced MBZ mechanics fall short in understanding. Thus you need to let the people who read this FORUM know exactly what you have... engine and tranny #(s).

I might help some and I know there are others who know a great deal more than me for my experience thus far is limited to the 1980 300D I purchased for my Son.
Regards,
Sam

mbzkid · #5 06-24-2006, 01:43 PM

This is a 300D Turbo Diesel, with a 617.xxx engine and 722.xxx transmission. Maybe someone can fill in the blanks, but I do not believe it really matters much.

If the engine is not making enough power, the shifts will be hard.

First thing you need to do, is find out what's wrong with the engine. Can you be more descriptive? Does it smoke? Does it take off OK, but eventually slow down? Does it surge or pulse?

300TD · #6 06-24-2006, 07:32 PM

Yes, it is a 300D Turbo diesel. I do not know the exact milage right now but will find out. As for power, it does not have power from the start. It takes a long time to get up to speed and will slow down dramatically on steep uphilss or even long gradual highway grades. No surges in acceleration. Just steady, slowly building power.

I do not know the status of the vacuum lines/connections. I will be replacing brakes on it in the next week and I will pop the hood to start to try to uncover any vacuum leaks/breaks.

mbzkid · #7 06-24-2006, 11:14 PM

Any smoke?

300TD · #8 06-25-2006, 12:12 PM

Typical diesel....Nothing excessive white, black or gray....

MercFan · #9 06-25-2006, 02:55 PM

Quote:

Originally Posted by 300TD

My concern is it's complete lack of power. It is dangerous in my opinion.

My car had the same symptoms when I got it - it barely (and I mean BARELY) made it up my driveway (~1% grade) - per advice from this Forum, here is what I did:

1) Cleaned the Banjo bolt (on the back of the Intake Manifold) -it was full of gunk - www.dieselgiant.com has a simple and effective pictorial on that.

2) I replaced all pressure lines (though you should try cleaning them first) leading from the banjo bolt to the switchover valve on the firewall (driver's side) - also thoroughly clean the switchover valve itself. Finally clean/replace the pressure line to the ALDA - this was key for me - having the clean passage from the Intake manifold to the ALDA did the trick for me.

3) Clean the boost protection switch sticking out of the intake manifold (should have a single wire coming out of it - be sure NOT to ground it...

4) What I did next was adjust the ALDA (3/4 turns CCW) and the vehicle 'came to life'... as per advice from others I would do this ONLY after you've got the above working perfectly.

5) Change all the filters (air, pre-fuel and main spin-on fuel filter) - no telling when they were changed last.

Do this first, post results.... there are many other simple steps to take, I'm sure others will jump in.

Good luck - let us know,
James

Maroon 300D · #10 06-25-2006, 06:58 PM

Changing the fuel filters and cleaning out the banjo bolt/lines are good ideas.

You might want to also check out the rack dampener pin on the car. It's basically a screw held into the injection pump with a nut. It's not hard to get to.

On my car, this pin was too tight, resulting in a loss of power at low rpm's. After I adjusted it the difference was significant.

Another symptom of a rack dampener pin that's not quite right is the car shaking after a highway drive.

It's extremely easy to adjust the pin, you should be able to find the procedure with a search for 'rack dampener pin.' I would also recommend taking it out and having a look at it, as sometimes they fail and new ones are required. It has a springy tip, so if the tip isn't springy, a new one is in order.

300TD · #11 06-25-2006, 09:01 PM

Is the rack damper also know as the Governor Idler Adj. Pin ?

All filters will be changed, I have done and will clean the banjo bolt and replace the lines to the overboost valve. How does one clean the overboost valve?

Once all of these items are complete (along with the valve adjustment). I will report back and let everyone know where the problem stands.

As I said, I think this is a good car for a new driver. I appreciate all the help that has been offered and I'm sure that I will have mor questions.

Thank you

Samuel M. Ross · #12 06-25-2006, 09:35 PM

InterNet parts sources know it as:
"Injection Pump Rack Dampener Pin" and one sells it for only $37.00... but I've heard that there has been an official MB upgrade to this essential part so IF you end up needing to buy one, you might want to bight the bullet and purchase it from your local MBZ Dealer's counter... and ask if there has been an upgrade to the part.

Samuel M. Ross · #13 06-25-2006, 09:38 PM

sorry... I forgot to tell you that your "Rack Dampener Pin" is # 109 in the attached edited IP parts blowup! I believe that a picture/sketch is worth a 1,000 words!
Sam

300TD · #14 07-11-2006, 09:22 PM

to continue.......

On the way to my house with the car, there was a total lack of power. Once it arrived, I cleaned the banjo bolt, adjusted the valves, replaced the injectors, added an algacide and fuel conditioner. The car started and ran fine, for awhile. Then it again had no power. I'm guessing it is a fuel delivery problem. The next thing to check is the screen in the tank, change the fuel filters and try again. How do I get to the tank screen?

Any other suggestions?

Thanks everyone

Samuel M. Ross · #15 07-11-2006, 10:27 PM

do the old "flush the fuel tank" trick!

The clue for me is that after you changed the fuel filters, things were OK, but only for a short while... and now the gremlin is back. Check that pre-filter again and if it is visibly clogged again so soon, then it's flush time... and while you are down there opening that big hole in your tank, you will have ample opportunity to check your screen for it comes out the bottom where you will flush... maybe it's deteriorated and all the "slduge" is carrying forward unimpeded forcing the pre-filter to work overtime.

IF you do end up flushing things, be sure to also blow air or even better force a good strong flow of "fuel" back through the line(s) from the engine compartment towards the tank! Yes, I do mean through both the supply and return fuel lines... pushing the "guck" there back where you can flush it out along with the other "sludge that normally settles in the bottom of the tank.
And for good measure later when you have the tank opened up, give these engine-to-tank line one more blast to clear out anything that worked it's way down from the tank while you were opening her up to flush.

I like to force fuel back through for a liquid is more forceful and thus thorough in cleaning these lines. Then you can use ~3 to 5 gallons of fuel [skimming clean fuel off the top of your bulk container]... use this to flush back into your fill pipe into and through the tank so it will carry more of the sludge out the bottom.
Obviously you do this until and for some time after you see clean fuel spilling out. Flushing can be messy unless you have a cheap pump to use and some way to effectively filter the suction side of your submersible diesel pump. A 12-volt "bilge pump" like those used on power boats might work if you can put together a filter setup around the pump.

You can do this safely only because diesel fuel has such a high flash point in comparison to gasoline with which you would be gambling with your life.

Let us know how it goes,
Sam