I just bought a Mercedes 300D - It's beautiful, an '80 with only 134k, and I love it, but it is EXTREMELY slow going up even the slightest grade. I expected it to be slow off the line, and merging, and for it to be slower on hills, but this is ridiculous! I didn't hit any big hills on the test drive - didn't even think to, and on the way home was struggling to barely go 15 or 20 up a larger hill and seriously thought I might not make it. Even on a slight grade it seems to lose a ton of power immediately - I've cruised on flat highway at 75 easily, but at times (was there a slight grade?) I had it floored and it wouldn't go over 60. Are these cars just totally gutless in general, or are there some adjustments/things to look for that might help? I'm wondering if I should get a turbo diesel instead. I really don't need a super zippy car - I mostly just drive my kids around town, but for the occasional hill, I'e truly never seen anything like it (even when I used to drive an old VW bus!)...The slowest of slow trucks were passing me and I think I singlehandedly caused a traffic jam...
I'm hoping to keep this car, can anyone HELP?
Thanks,
honeytiff

Welcome to the forum

1) Pull on the knob just above your left knee. With the E-brake off it goes faster.

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'81 280SEL

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81 300SD -
93 300E w/ 3.2
85 300D-
79 300SD
82 300CD
83 300CD - CA
87 190E 5 spd
87 Porsche 924S

"..I'll take a simple "C" to "G" and feel brand new about it..."

Are you serious? I'm not driving around with the emergency brake on!!!!
I'm actually looking for some helpful advice - would that it were so simple....

I am having the same problem with my 1980 300D.
In my case I am very carefully following all the archive advice
regarding throttle linkage settings and vacuum issues.

You are probably doing the same. But I know what you are talking about.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

i bet your fuel filter is clogged. i had the same issue while driving to california. i was doing fine on the highway, then after some time i noticed how it would slow down on hills. then later it got so bad, that cruise control could not even keep it above 45 mph. i got off the next exit, and almost kicked mylself for not thinking of it earlier. i replaced the fuel filter (took me less than 10 mins) and was driving 85mph after that.

go and replace that filter...

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Grey '91 350SDL 214k Dad's car
Beige '81 240D 4 Speed 254k SOLD
Blue '82 300D 225k SOLD
White '95 E300D 46k SOLD
Blue '87 190D 2.5 Turbo 315k SOLD
Brown '80 240D 4 Speed 716k SOLD
Beige '80 300D N/A 119k SOLD
Blue '85 300D Model 186k T-Boned

I am new to mercedes and am not familiar with throttle linkage or vacuum system specifics. I know that the AC doesn't work and that it may have to do with the vacuum system - could this be effecting acceleration? Someone suggested fuel filters...?
Thanks

Thanks for the fuel filter advice! I'll definitely try it!

I had the same problem with my 300SD when I got it. There is a little unit
on the driver side of the firewall. It has two lines coming from it. One goes to
injection pump on the side of the engine, and the other goes to your intake
manifold. It also has a two wire going to it. Mine had one of the lines cracked.
I fixed the line, and works perfect now. My friend drove his 300CD for 4 years
without this unit working. It was slow as my ass...So I took mine off and put
it on his. He was shocked at how much faster it was. He was pissed that
he drove it for so long like that. You should feel the turbo kick in at 2200-
2500 RPM. Also you should check the kick down cable. The adjuster is on top
of the valve cover. I set mine this way. I move the linkage to full throttle,
then move the exposed cable left and right. There should be about half an
inch play from side to side. This worked good for me but you might need it
a little looser. If it will not shift, it is too tight. If it does not kick down when
you floor it, it is too loose. Hope this helps.

i agree, its probably a fuel filter and its one of the easiest things to check/replace. if you just bought the car and dont know when the last time it was changed i would recommend a diesel purge (to clean out the injectors) then changing out the 2 fuel filters afterwards. you might also want to check out your air filter they get clogged w oil blow by. if youre not familiar w doing a purge theres plenty of information on this board. Diesel Giant has a great step by step pictorial on his website. good luck!

Here are the steps that I followed. It only got peppy when I finished the list.

Replace all filters, including the one in the fuel tank.
Replaced injectors
Set injection pump timing
Ensure valves are adjusted properly

It's not a rocket, but going up a long steep grade, it will maintain 55 mph or so. On the flat, top speed used to be 70 or so. Now I can do 85 with out the pedal to the metal.

One more thing,,, get a good running start and as one smart guy once said,,, drive it like you stole it.

JCD

I also had the exact same problem with my 81 300D when I bought it.

Changing the fuel filters worked for me.
There are three filters on my car.

The first one I canged was the small plastic one by the Injection Pump.
That made a world of difference.

I changed the spin on filter second.
Did not notice much difference if any.

Then I found the filter in the fuel tank.
Changing it made a little difference.


Other things have helped also.
Setting the valves.
Setting the ALDA
Getting the transmission to shift better.


Things I plan to do that I hope will help.
Cam chain timing, or replacement.
Injection Pump timing.
Fuel injector replacement.


Hope this has helped.
Welcome to the board.

RichC

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When the power of love overcomes the love of power the world will know peace.
Jimi Hendrix

is always the fuel filter. this is most likely your problem. remember there are two to change. after changing them you will need to use the prime pump to get the air out. if that fails you can remove the air cleaner and spray wd40 right into the intake. the car will run on the spray til the fuel line is purged of air.

if you find a lot of black dots in the small fuel filter you have fungus in the tank. this will require a few doses of fungicide for diesel fuel buyable at truck tractor and marine suppliers.

good luck

benz diesels are the best!

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

As most people are telling you, your 1980 non-turbo 300D should not be this weak. You should have no problem going at highway speed up moderate grades.

Since you just bought it, there is some chance that it has not been properly maintained. Plus, many people who have these cars do not realize that they require certain kinds of maintenance that other cars do not.

In my particular case, I bought a 1982 turbo 300D that seemed fine at highway speeds but was very weak doing something like going up a steep parking lot ramp. This turned out to be a problem with the linkage from the accelerator pedal to the engine's fuel injection pump control. There is a pivot swivel attached to the firewall of the car on the driver's side, where the motion of the pedel depression is changed to a rotating movement. The original design used a plastic that would decay with time, and it was loose. This prevented the car from getting it's full fuel injection even though the pedal was floored. Once this $45 part was replaced the car drove as expected - plenty of power.

Other people have mentioned the fuel filters and valve adjustment. Good ideas on a new 300D. There are two fuel filters under the hood, one is a screw-on can that looks a little bit like a spin-on oil filter. It's on the front of the engine held by a bracket - the rubber return lines from the fuel injectors loop from injector-to-injector from the back to the front of the engine, and then go to this bracket. Then there is an in-line plastic fuel filter much lower on the driver's side of the engine compartment. This is really just a strainer but it gets clogged sometimes.

These cars require a manual adjustment of the valve clearances. Most cars in the USA don't require this and people sometimes never have it done. As a result the valves get tighter and tighter and prevent the engine from "breathing" properly. Adjusting the valves is not too hard if you do typical mechanical things on cars - otherwise it's about $200 at a mechanic's place.

If you want to work on the car yourself, the best manuals to have are the Haynes W123 manual and the Mercedes factory CDROM. Both are often found on EBay. Actually, better than the factory CDROM are the paper book manuals, but they are getting rare. Mercedes just scanned the books and placed the images on CDROM to sell rather than printing more books.

Let us know how things go for you. Parts are available from this website, click on the "Fastlane" icon at the top of the page.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

honeytiff,

So that you are not confused by some of the posts, there are differences between your car and the later turbocharged models. One person suggested an ALDA adjustment. You can forget that because your non turbo car has no ALDA.

When buying any used car, it is a VERY good idea to go through and change fluids and preventive maintenance items. As correctly stated by most responders here, change the fuel filters. Start with the can filter and plastic filter that are on the drivers side of the engine.

If you do your own work you will need to follow the correct procedure when changing them or your car will not restart.

Pull the can filter and then pour the new filter 90% full of diesel fuel and put it in place. Then replace the plastic filter and get it all tightened up. THEN you will see a round plastic knob near the plastic fuel filter. Rotate the knob counterclockwise until it is released so that you can pump it up and down. It might leak a little while pumping but don't worry about it. Pump it up and down until you hear a hissing sound at the top of the can fuel filter. Once you hear that sound, push the pump back down and turn it clockwise until snug to lock it back in place.

Drive the car then and see if it will pull hills more to your liking.

The other thing that I would say, is that if you are not accustomed to one of these cars and have been driving a much more powerful vehicle, then it might just be that you are not used to the lack of power. These cars will pull hills okay if in good running order, but they won't accelerate very much uphill.

Another potential problem is that the transmission may not be kicking down as it should. These cars have a contraption on top of the valve cover and a valve on the back of the injection pump that SIMULATE the vacuum conditions found in a gas engine. This is what feeds vacuum signal to the modulator valve on the transmission and make it shift when it should.

If changing the filters, which should be done anyway, doesn't give you some power, then go to a steep hill and manually down shift it with the stick into a lower gear and see if it pulls the hill as you would expect. If it does then you will need to see to the vacuum contraption on the valve cover and the valve on the Injection Pump.

Best of luck with it. If you have bought a car that does not use too much oil, you will be able to get everything else in shape and have a good car.

Enjoy,

Other than th eusual culprits (filters) it could very well be the linkage is out. My 240D was running fine and then I had the valves adjusted and when I got it back I coudln'e get it o go any more. It turned out to be the linkage had been screwed up. Had the linkage adjusted and now it goes better than when I first got it.
What happens if the linkage is out is that the IP does fully throttle open and hense no juice=loss of power. When my linkage was off I had to drop it to second to get up a hill whereas I could easily climb it in 4th before.

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