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  #1  
Old 05-03-2015, 11:43 PM
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Unhappy 1979 Mercedes 240D Auto top speed 68 MPH??

Hi, guys, newbie here.

As we all know, the 240D auto is stupid slow.. But mine is so slow that I can't get the thing over 68 MPH on the highway. I have replaced both fuel filters, ran a bottle of straight diesel purge, opened up the throttle stop, and even tried running the car on a separate fuel container to make sure the strainer in the tank isn't clogged up.
I have always ran Diesel fuel only. The car has never seen SVO,Bioiesel or WMO in the time that I have owned it. I've run out of things to check/replace.. Any advice? Thanks!

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  #2  
Old 05-03-2015, 11:55 PM
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Have you checked\stretched you lift pump return spring? Do a search on it. It can make a big difference or so I have read. Have you adjusted the valves yet?
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  #3  
Old 05-03-2015, 11:56 PM
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Adjust your valves. One of the more important maintenance items. Also, what is your differential gearing? Condition of injectors? The car may be slow going from 0- to whatever, but that should not effect the overall top speed. Also, is your speedo accurate? I double check mine with my daughter's Garmin.
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  #4  
Old 05-04-2015, 12:47 AM
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When I bought the car about 3 months ago, I was told that the valves had been adjusted, and the lift pump was replaced with a new one prior to purchase. The guy I bought it from is a Mercedes mechanic, so I trusted that he knew what he's doing. The car has been slow like this since the day I purchased it, but I just assumed that it was really just THAT slow! Ha! The condition of the injectors is unknown, I will have to take a look here in the next couple of days when I have some time to mess around. Gear ratio is unknown. I have checked the speedo accuracy with my GPS, and its right on.

If I was having lift pump problems, would it act like its fuel starved? It doesn't appear to be behaving like its fuel starved at all. Just low top end speed.

Last edited by sparty411; 05-04-2015 at 01:21 AM.
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  #5  
Old 05-04-2015, 02:04 AM
dkr dkr is offline
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I would lubricate the linkages and check to see if the throttle needs adjustment. You could also have a plugged EGR or a stuck valve. Also, change the air filter if it is overly dirty. Following that, make sure the ADA is connected properly and you can try turning it to adjust the air/fuel ratio. It sounds more like a breathing problem -- like something is clogging the intake or exhaust.

Dkr.
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  #6  
Old 05-04-2015, 03:16 AM
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In tank fuel screen could be plugged up.
Also when you remove the Fuel cap, is there a whoosh of air>
Could be a plugged tank vent.

Charlie
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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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  #7  
Old 05-04-2015, 03:59 AM
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Top speed on that model should be able to slightly nudge or eclipse 80 mph, FYI.
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  #8  
Old 05-04-2015, 04:16 AM
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Before I started getting crazy, I pulled out the air filter and its covered in dirt and completely soaked with oil.. I'm a novice when it comes to working with cars. What does this mean?
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  #9  
Old 05-04-2015, 04:26 AM
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The engine can't breathe properly.
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  #10  
Old 05-04-2015, 04:29 AM
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But why would I be getting such a ridiculous amount of oil in the air filter?
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  #11  
Old 05-04-2015, 08:41 AM
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it's called blow by, proof of worn or stuck piston rings
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  #12  
Old 05-04-2015, 09:35 AM
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Or perhaps someone used an oil bath air filter. Was the element paper or metal?

Also, your engine may just be tired. 80-ish mph requires the full output of the engine when it was new. But valves and compression are what I would look into next.

What mpg do you get? What is you 0-60 time?
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  #13  
Old 05-04-2015, 09:54 AM
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does your car have an oil seperator? if not, you may want to get one installed. any 82+ 240 will have one. not sure about the 79's follow the tube from the valve cover to it's termination, and see what it's hooked to.

FYI... unable to reach higher speeds, or unable to accelerate as fast as normal is the definition of fuel starved... inspect the primary filter, sometimes they have too small an opening that restricts fuel flow. and sometimes they clog up with a clear goo from bad fuel.
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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
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  #14  
Old 05-04-2015, 10:52 AM
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If the 79 is like my 80, then the blow by tube goes straight into the intake manifold, not into the air filter.

Using a oil separator like the 82 -83 240 uses, there has to be the drain tube going into the upper pan which the 79 does not have.

Charlie
__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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  #15  
Old 05-04-2015, 11:06 AM
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Quote:
Originally Posted by charmalu View Post
If the 79 is like my 80, then the blow by tube goes straight into the intake manifold, not into the air filter.

Using a oil separator like the 82 -83 240 uses, there has to be the drain tube going into the upper pan which the 79 does not have.

Charlie
this is a good point...

how is the oil getting to the filter?

OP, can you take a picture of the engine?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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