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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #1
Got car this weekend. Very BAD acceleration. So bad, I can't pull out safely. I can't even drive it. It takes too long to get up to speed. This is a continuation to my "Diagnose this thread", so bear with me. Here's what I did so far.

1. Adj Valves
2. cleaned out fuel lines (cmpressd air)
3. Cleaneed out return lines.
4. installed new filters
5. Tightened up linkage
6. cleaned fuel tank screen
7. cleaned out ALL banjo bolts (turb intake, IP, Fuel)

My problem is, when I push down on the IP linkage, the car doesn't start to build up revs until it's almost touching the throttle stop bolt. Up until full throttle, the car just putters around at 1200-1500rpm. Once its full throttle, I can rev it pretty good by hand and keep reving it over adn over. If I let it go back down to idle, it takes a while to get it up to revs again- very slowgetting back to revs. I'm pretty good about doing mechanic work on these cars, but I can't figure this out to save my life! I'm ready to call it quits and do a motor swap witha Non-Turb motor *ouch!*.

Can bad injectors give this slow acceleration symptom?
A Bad IP? (I assumed it's worlking good being able to rev it up high)
IP Timing off??
Low compression?? will this give the super slow acceleration symtom??

HELP! I can't take it!!! Thanks guys!
 

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77 240d, 02 Ford F250 V10 (7mpg), 05 GMC Denali (The Baby Hauler), 2000 BMW 323CI (was my Bros car)
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817 Posts
Have you tried adjusting the alda? I would take note at its position and in small increments adjust it "in" or "out" and see if it changes anything. Also, how much fuel is it getting? It might be running super rich and it takes awhile to burn it out.
 

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1991 300 SE
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18,534 Posts
I assume you’re referring to your 81 300 SD 126 chassis car? The US market 300 D did not have a turbo in 81.

A compression test would be good place to start.
 

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Premium Member
W-1-2-3 Go!
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16,161 Posts
The throttle linkage has a bushing at the firewall, degrades over time, and causes increased play in the linkage and delayed throttle input, if at all. Look up "firewall bushing"

Also make sure the 10mm bolt on the linkage is tight. Can also lead so similar symptoms.
 

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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #5
Sorry, typo. It's an '82 300d. The Alda WAS messed with with the PO. I tried every setting with it. IN and OUT adn All the way out. It seems like it's starving for fuel at first, but i made sure that I cleaned everything all the way to the tank and every line. Can a stuck open wastegate do this? The car starts fine, idles a little rough for my taste, but not so bad that it causes concern. The linkage is a little loose even though I adjusted it. The PO did everything in the book WRONG to it. PIsses me off to say the least. I was thinking the injectors were bad. I can hear the turbo spool up so that seems good. I bypassed the overboost sensor behind the brake booster so that can't be it.

Can a bad IP still rev an engine good?
Bad Alda? Remove it completely?

What the hell? I can get up to highway speeds on level roads fine after the turbo spools up although it takes a good 30secs or so, but throw a 15* hill in there and I'm roadkill! I hope someone can figure this out for me cause I sure as hell can't! LOL!

=
 

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'77 6.9, 74 240D, 96 Ram 5.9L Cummins
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2,654 Posts
Is the turbo seized? I saw some 300D's at the junkyard and some couldn't be turned!
 

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77 240d, 02 Ford F250 V10 (7mpg), 05 GMC Denali (The Baby Hauler), 2000 BMW 323CI (was my Bros car)
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817 Posts
If the waist gate is stuck open you wont build boost. I would buy a cheap boost gauge and install it. That would at least tell you you are building boost or not.
 

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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #8
I hope more people can chime in on this problem. I'm aalso thinking that the timing is off so the IP pumps late, which in turn shows the slow acceleration issue but i'm not sure. I really hope someone had this problem before and can steer me in the right direction before I make repairs that are not needed. I just need to get this car going. It's my primary car, so I can't have a lot of down time. THanks everyone!
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,446 Posts
Do you still have the other Benz's listed in your profile? Why would this be your primary car if you've only had it two days and it has not run right since?

I'm not sure how you'd do a fuel pressure test on a diesel, but I'd imagine there's a way. I've never had this problem with one of these before.

I'd check the waste gate, as somebody mentioned, a vacuum/boost guage would definately be a useful tool.

Other than that, do a compression test. How much blow-by is there (warm)? Lots could indicate bad rings, and poor compression will cause a huge power loss. Although, my 300CD (non turbo) has more blowby than exhaust, and once it runs perfectly fine. I estimate 300K miles on it, and I drive it every single day and I see no reason not to drive it until it craps out. Adjusting IP timing might be a good thing to try also. I'd try advancing it a LITTLE bit... don't go moving it all the way.

Either way, a 250K mile Benz turbo-diesel is just a decently broken in engine. Typically, they go good for 300 at least.

Aaron-
 

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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #10 (Edited)
This is my primary car. I just sold my 300 and bought this one. This one has zero rust adn a turbo 617 motor, a major find for me in Hawaii (no rust) and although it ran this way when I got it, i figured the solid rust free body was worth the PITA of getting it to run good. Every w123 here is a rustbucket, so when I found this one, I jumped on it...I've been through a few w123's since my profile post so I no longer have those cars I have listed. I'll change it.

Anyways, back on track. I also thought a stretched chain would do this? Maybe I need an offset woodruff key? Damn, I may as well just do a rebuild on this motor or swap it out for my 300cd non-turb motor. I know that runs ok, but the turbo! I want the turbo!

*I don't get why the car only revs on the last 1/4inch of the throttle range when I push down on the IP linkage manually. THen it revs fine, but up until WOT, it revs up slooow. like vvvvvvvvvvroom, vvvvvvvvvvroom, NOT vvroom vvroom! LOL! Thats the best way I can explain it.
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,446 Posts
Start figuring it out? Try all of the tests that myself and all of the others have mentioned and see where it leaves you... You've made it clear that the engine is horribly unresponsive. Now you have to figure out why.

Stop jumping to conclusions of bad timing chains and the like when you have yet to perform a simple compression check that requires a wrench and a small amount of time.

And don't get irritated when nobody can provide you with an answer to a problem when you've done basically no troubleshooting. You've replied to your own thread a number of times, but you've never come back to say that you've actually tried some of these basic tests.

No power and poor acceleration is the oldest complaint in the book about ALL engines.... you have to actually figure out WHY your engine runs crappy. Nobody is going to just tell you to twist a screw three turns to the left and it'll run like a brand new car. Very few things make these engines run. Fuel, air, compression... You need them all. Do you know if you're getting enough fuel? probably, but maybe not. How about air... Who knows, check the turbo. Can you hear it working? If not, replace it, if so, check the waste- gate. Compression? Grab a guage and find out. These are THE most basic things any mechanic will check on an engine with this complaint.

I've been chasing an idle problem on my M103(gas) for weeks, and I've been all over that engine a hundred times. Get dirty! It's half the fun.
 

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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #12
akimball, I actually HAVE tried all the suggestions everyone has given. I don't expect to find any easy fix from others. I'm simply trying to find out from others what they have don't THEMSELVES with a similar problem, not what theyve heard, or read to do. I KNOW someone has to have gone through this problem. You say get down and dirty? I've been down and dirty for 3 days now trying everything under the sun short of doing a complete rebuild and this is why i'm so stumped! I've done work on these diesels for some time now and I've never needed as much help as I do now. I live in a remote town in Hawaii and the last thing any auto parts store has in stock is a diesel compression tester! I need to order that. Well, sorry if I came off they way you made me out to be. I'm just here for help like everyone else. Again, for the record, I have done every test sugested by other members which I appreciate, like it says at the end of every post. AS everyone knows too, if they everything they think is wrong with their car besides the actual problem, it does get quite costly.
 

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Premium Member
W-1-2-3 Go!
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16,161 Posts
*I don't get why the car only revs on the last 1/4inch of the throttle range when I push down on the IP linkage manually. THen it revs fine, but up until WOT, it revs up slooow. like vvvvvvvvvvroom, vvvvvvvvvvroom, NOT vvroom vvroom! LOL! Thats the best way I can explain it.
See if you've adjusted the linkages properly. I've once experimented with different throttle settings, it looks like you adjusted it the wrong way.
 

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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #14
thanks karugs, but i'm almost positive that the linkages are ok. If not, my throttle would have a 1/4" travel which I know is not right unless it's a race car. I check the timing today and it's dead on. I also tried running the car w/ the brown shut off vac line disconnected. No help. I think the compression is good because it's hard to turn the motor manually adn doesn't turn by the power steering belt pulley bolt at all. UNLESS the piston rings are binding on the sleeve/cyl wall, which could cause this symptom along with the low idle (which I have). I sure as hell hope not. I can start the car fine, and it doesn't seem like it's laboring to turn over. It sounds good, so again, I'm ruling out binded rings for now. PO said it just stopped working one day and it was driving fine previous to that day so it doesn't seem like the case with the piston rings. No oil in water or vise-versa. The fuel tank vent is clogged, but i drove it w/o the cover on but it only helped a tiny bit. I blew out all the other fuel lines w/ compressed air and all seem fine. I also blew out all the injector hard lines and cleaned them good, inside and out. The only thing I didn't check is the wastegate. If it's stuck open well, I'll have to work on that somehow. I'll check boost later today and I also want to check the primer pump for leaking air. It doesn't weep fuel when I prime it, but i'm thinking that maybe that could be clogged somehow or air is getting in somehow. I'll post back in a couple hours.
 

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"Sadie"1984 w123 White/blue 169K and counting. The Grey POS or parts car 83 grey/ palimino
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150 Posts
Are all the fuel lines crack free? I had a problem that was similer to this and there was a crack in the short fuel line from the primary filter to the pump. Also, if its running, I'd look at the primary filter for bubbles. You 've done the valve adjust, did you double check the clearances? Did you try a purge? Maybe some gunk is built up on the injecters. I'm not sure, but can a loose glo plug reduce compression?

I'd find out as much as I could about what the PO did, and undo it. He may or may not have a clue as to what they were doing. As far as the alda, perhaps someone knows the baseline setting. Come to think of it did you check the vacuum lines for leaks that would make these not work at all. It seems to be a combination of things that are wrong.
 

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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #16
Here's the latest:

checked valves again- good
checked cam timing- spot on
shortend ALDA hose 1", small pinhole but no effect after fix
checked wastegate hose, perfect
redid linkages for good measure
adjusted rack damper- smoother idle now, but no help to orig problem
all fuel lines are good- no cracks/leaks
all fuel filters new
10mm linkage bolt tight as can be and in correct place.
I've been under that hood waaaay too long for this problem. I really could have done a complete rebuild it in the same amount of time. Problem is still the same, when I press the gas it putters around 1000rpm-1500rpm for about 3-4seconds before it starts to build up to the 2k range and above. Once above 2k, it's fine and can keep revs up from there.

I just don't understand why it only starts to rev 1/4" before it hits the throttle stop bolt. If i let it back down to idle adn press the throttle again, sa,e thing. Putters and slowly builds to 2000 rpm, after 2000rpm it's fine. It's the 1000-2000rpm that's giving me trouble.

Thanks for all your guys help and suggestions.
 

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1981 300cd, 1981 300sd
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53 Posts
Discussion Starter #17
DAMN!! I just thought of something. The PO had this joe schmo idiot work on it right before I took it, and when I brought it home, I noticed they changed the injectors from my previous original inspection. I think they took out the "new" turbo injectors and swapped them for some crappy turbo AND non-turbo injectors knowing i'd be taking it home and they could get some freebie injectors! I really think this may be it. Can't believe there's people doing this to these cars. PO said she'd buy me new injectors, so we'll see what how that goes.
 

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Premium Member
'84 280sl 5 speed
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432 Posts
Okay, so I read this post all the way through because I am having the same problem. I get to the end and Asghilo leaves us hanging! Was it the injectors?! Did the car ever find its acceleration? And, what about Billy Joe and the Pakistani?
 
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