w124 300d 1989 losing power over 70mph

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muggsy

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Oct 23, 2005
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hi all first of all i would just like to say keep up the good work on this excellent site just found it.
anyway when my 89 300d w124 gets up to 3000 rpm in top gear it seems to be losing power,chugging,but its ok when im going under 70mph.any help greatly appreciated
 
Welcome to the forum.
Might need a diesel expert to confirm/deny and diesel related quirks, but can you tell us if your car has cruise control and/or non standard size wheels.
Some vehicles have problems with the latter.
Or could it be a partially blocked fuel filter ?
 
Hi

I would try try the pre filter and the main fuel filter.

230K
 
hi guys thanks for the help the car doesn,t have cruise control and its the standard mb 15" alloys.today i took the revs up to 4000 and it sounds fine it just seems to be when the car is in gear and running,its more noticeable in the morning when the car is cold. any ideas?
 
Losing power

I'd be suspicious of the gearbox, particularly if it's got a few miles on it. Which it should have, being an '89 diesel!

One thing I had occasionally with my '87 250TD was that the shutoff valve remained partially closed and this caused the car to lose power. I found that if you turned the engine off and restarted it immediately it would stall or run down on power as the shutoff wasn't fully open

The shutoff is under the inlet manifold below the gap in the inlet tracts - give it a pull upwards to make sure it's open. If you get someone else to switch the engine off whilst you watch it you'll see it drop down as the valve closes

I think it's down=off but can't quite remember!


Nick Froome
www.w124.co.uk
 
funny you mentioning the gearbox i can hear a very slight whine (not a bearing whine ) i wasnt sure if it could be the gearbox or the drive unit think i will get the oil changed in both and see what happens.can this cause a lack of power?
 
Whining diesels

No, the whining will be the back axle!

Check the fuel shutoff valve first, then change the filter & prefilter


Nick Froome
www.w124.co.uk
 
Also it won't harm thing to run some injector cleaner through the system, as your injectors could be slightly blocked......Instead of using injector cleaner, I used to sling a litre of Automatic Transmission oil into my fuel tank. It does a great job of cleaning the fuel lines and injectors and many long term high mileage diesel owners in the US swear by it. After that I would also change the fuel filter as has been suggested.

It would also be a good idea when running the injector cleaner to give it an "Italian Tune Up", ie give it a good run with plenty of revs, ie 4000rpm gear changes.....even better if you can do this up a steep hill as diesels benefit from driving them under load ever so often, as it helps to clear the carbon in the combustion chambers.

Good luck
 
cheers guys i will try out your suggestions next week when i get time.will let you know how i get on
once again thanks
 
Firstly check the fuel unions for air leaks.
Your engine requires more fuel when under load so it will suck harder on the fuel pipes.
Any leak will be exacerbated.

The problem definately sounds like fuel starvation.
 
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hi all thanks for the advice changed the two fuel filters and its going fine now the prer filter was the problem
 
Hi

Glad you got it sorted.

Enjoy

230K
 

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