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1982 300SD
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19 Posts
Discussion Starter · #1 ·
I never really beat on my old girl... Affectionaly called "black betty" But I decided it was time for an italian tune up and on my way to work I aimed for 100mph.

At 90mph the engine would pulse and not accellerate any futher. I understand these cars are speed limited by the injector pump, but I think it is limited to something over 100 mph.

Any ideas or information as to why it is doing this?
 

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1991 300 SE
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18,534 Posts
Engine speed is governed rather then actual vehicle speed. As you know due to the final gearing the engines rev high on the highway even at regular speeds.

Questions: what was the RPM at 90? Why did you feel the need for an Italian tune-up, how was the engine running before? How many miles on the fuel filters, air filter and tank screen. Was there excessive smoke? Motor mounts may be an issue as well.

Depending on the miles and over all condition of the engine (compression in particular) 90 may be her top speed.
 

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1982 300SD
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19 Posts
Discussion Starter · #3 ·
I have about 1,000 miles on the current fuel filters, and air filters. The status of the tank screen is unknown. Maybe something I should look into. As for the desire for an "Italian tune up" I just felt like it. There was nothing that make me think it needed it, just felt like it. When she accelerates she goes strong, obvously no rocket ship being she is diesel but acceleration is smooth and responsive to the accelerator.

I have 189,000 miles on it. Maybe I am not getting into the final gear? I read alot about the OM617 but never really did any studying on the transmission.

Any other 300SD owners out there? What have you taken your SD up to for high speed?

I need to get a new tach amp because mine is jumping around all over the place sometimes and dead other times. This would be a key issue in understanding what is going on with engine speed and this issue

-Michael
 

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1991 300 SE
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Remember that the car starts in second, you should detect the up shift from second to third and third to fourth. A partially clogged tank screen can restrict fuel flow to the engine at high demand, the effect may not be evident during otherwise normal driving. A compression test would give you an idea as to the amount of valve train and ring wear and the consequent effect on horse power produced. A check and adjustment in the throttle linkage may be in order. Some Diesel Kleen in the tank and/or an IP purge wouldn't hurt and might clear up the problem.
 

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Depends on the day!
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How much blow by does she have when warm? Next time she's running pull the breather hose and cover it with your thumb...count off how many seconds before she wants to stall..

When were valves adjusted last? Injectors done last? Timing chain?

FYI, one does not need to drive excessively fast to give a car an Italian tune up..it's RPM's you are looking for, pref. achieved w/ WOT.. So you can accomplish this in the first few gears w/o issue.

Jonathan
 
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