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  #1  
Old 12-31-2017, 01:19 AM
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So I bought a 300D

I bought a 1980 300D today, Ill have to pick it up in a week or two but... Before I get it and start messing with it, it has a few issues I need help wrapping my head around. Its a N/A so it barely gets out of its way anyway, but in this car the throttle pedal goes 3/4 of the way down before the engine even starts to rev from idle, it really kinda sucks. Also it has no more of the chrome lines that travel the length of the car anyone know where I could source replacements? And the last and worst part, it has a knock from hell. Ive owned 2 diesel pickups a powerstroke and a cummins. So im familiar with the noise, but thos is a loud knock, definetley something wrong, guy said it was lifter knock? I have no idea I think in might be a valve, doesn't sound like a rod but then again ive only known catastrophic knocking from a honda I blew up for no reason other than that it was its time to go. Could anybody point me in the direction of the knocking and help me get it roadworthy.

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  #2  
Old 12-31-2017, 07:09 AM
t walgamuth's Avatar
dieselarchitect
 
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Location: Lafayette Indiana
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Where to start.... first, welcome to the old diesel mercedes hobby. The 300 na should provide liesurely acceleration up to a top speed of at least 90 if in good operating condition. The accelerator linkage sounds like it may be missing some key rubber components and not providing full travel on the injection pump, so you can check that with a helper pushing the pedal.

As for the knocking it does not have lifters so it must be another issue. I suggest you make a video with sound and put it up so we can listen to it.
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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.
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  #3  
Old 12-31-2017, 07:16 AM
Bengoshi2000's Avatar
1991 300D 2.5 Turbo
 
Join Date: Jan 2011
Location: NC, USA
Posts: 360
What walgamuth said... post a recording of the sound.

Could be injector nailing... My 300D was nailing so loudly it sounded like a ball peen hammer hitting something. Two tanks of B99 and a set of fuel filters later, no more knock.
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1985 Mazda RX-7 GSLSE
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  #4  
Old 12-31-2017, 11:54 AM
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Thank you guys, Ill post some pictures and whatnot of my new 500$ family car as soon as I pick it up and get it home.
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  #5  
Old 12-31-2017, 11:56 AM
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If by the "chrome lines running the length of the car" you mean the impact absorbing strips down the two sides of the car. I'm afraid you are in the same boat as the rest of us. I'm trying to repair/replace the right front and passenger door ones myself on my 123 but no luck. You have to search online and check out wrecking yards and such.

As for the accelerator issue. The fire wall thingy is likely perished and not transmitting full accelerator travel to the injection pump. Easy fix.

Can't comment on the engine sound. Sorry.

- Peter.
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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S
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  #6  
Old 12-31-2017, 02:57 PM
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Wait, so one question I have to drive the car about 20 miles to get it home but with the throttle issue it only hits about 45. I dont have to get on the freeway however this is TX and 45 on the highway is dangerous big time. Is there a quick way I can rig it to ge full motion back.
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  #7  
Old 12-31-2017, 03:08 PM
Diseasel300's Avatar
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Have someone press the pedal to the floor and watch the throttle linkage at the injection pump. If it doesn't go to full travel (hitting the stop on the back side of the pump), shorten up the accelerator linkage until it does. It'll get you home at least, once you're there you can worry about setting the rods to the correct length and replacing the firewall pivot bearing if it's toast.
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  #8  
Old 12-31-2017, 04:41 PM
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What others have said: make sure it's the accelerator linkage and not something wrong with the engine or injection system. As the gas pedal is pushed down, the end of the wonky linkage connects to a pivoting bracket down between the engine block and the injector pump. If you examine the area you'll see the idle stop (a vertical screw with a jam nut) and the limit screw (oriented horizontally not too far from the idle stop) with corresponding tabs of the throttle bracket that make contact at idle or wide-open throttle. If the gas pedal is to the floor and there's quite a bit of travel left before that bracket hits the full-throttle stop, your throttle linkage has an issue and band-aiding it is as much your guess as mine.

Better yet, have a picture. You're looking at the injector pump from, basically, inside the engine - that black apparatus is what I'm calling the throttle bracket and the arrows point to the idle stop (right, lower) and WOT stop (left, upper).
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So I bought a 300D-4521-m67t-2t.jpg  
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  #9  
Old 12-31-2017, 05:04 PM
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Rogue T Tolerant
 
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Definitely check throttle linkage play. The engine should start reving with a big of throttle. The NA om617 is slow, but not the worst slug in the world.
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  #10  
Old 12-31-2017, 08:11 PM
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Knock

I have had several of these with a knock, and none were injector nailing. Far too often they are run out of oil until it is too late-damage done. Usually the engine will miss if an injector is nailing. Smell the engine oil. If it smells at all burnt, nailing is not the problem.
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  #11  
Old 12-31-2017, 08:25 PM
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Location: Phoenix Arizona. Ex Durban R.S.A.
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Quote:
Originally Posted by Diseasel300 View Post
once you're there you can worry about setting the rods to the correct length and replacing the firewall pivot bearing if it's toast.
If the firewall pivot bearing is cracked but still in place. In other words it's only transmitting some of the pedal travel to the injection pump, you might be able to brace it by wrapping wire around it as a temporary measure till you get it home.

- Peter.
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2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S
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  #12  
Old 12-31-2017, 09:36 PM
koooop's Avatar
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Upgrade to autoclub premium and have it towed home to prevent unecessary damage.
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  #13  
Old 12-31-2017, 10:05 PM
t walgamuth's Avatar
dieselarchitect
 
Join Date: Apr 2005
Location: Lafayette Indiana
Posts: 38,613
Quote:
Originally Posted by pj67coll View Post
If by the "chrome lines running the length of the car" you mean the impact absorbing strips down the two sides of the car. I'm afraid you are in the same boat as the rest of us. I'm trying to repair/replace the right front and passenger door ones myself on my 123 but no luck. You have to search online and check out wrecking yards and such.

As for the accelerator issue. The fire wall thingy is likely perished and not transmitting full accelerator travel to the injection pump. Easy fix.

Can't comment on the engine sound. Sorry.

- Peter.
I have straight side trim I'll sell reasonably.
__________________
[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.
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  #14  
Old 01-01-2018, 02:36 PM
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Most of the trim for a sedan is available from our sponsor. Around $15 each piece. The trunk lid trim is NOT available anymore.
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  #15  
Old 01-01-2018, 03:24 PM
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Join Date: Dec 2017
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So worst case scenario, it has a rod knock. Would an OM603 or OM605 fit pretty easy if i can source one?

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