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  #1  
Old 05-09-2005, 02:21 PM
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Question Sluggish 85 MB300D TURBO

My engine runs smooth but very sluggish especially on take off. Turned the fuel injector pump set screw all the way open but no help. Changed all filters. Is this a vaccum leak or other problem?

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Old 05-09-2005, 03:10 PM
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Quote:
Originally Posted by greaseup
My engine runs smooth but very sluggish especially on take off. Turned the fuel injector pump set screw all the way open but no help. Changed all filters. Is this a vaccum leak or other problem?
exactly what set screw did you adjust.....there are more than a few on these...
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Old 05-09-2005, 03:15 PM
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Sluggish on take off only can often be fixed quite dramatically with an ALDA adjust. The ALDA is on the IP; is this the screw you adjusted???

Sluggish overall with perhaps flaring on shifts is often caused by loss of turbo boost pressure signal to the IP.
Blocked banjo on back of intake manifold, or a failed pressure over pressure switch on the intake manifold are the most likely culprets.

There's no screw you should be messing with on the IP for your problem. The only normally adjusted screw would be the idle speed screw

Bruce McCreary
(2) '85 300Ds 83 300CD
Snowflake, AZ
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Old 05-09-2005, 03:43 PM
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Even beyond the ALDA mentioned above...

Sometimes the IP just dies and no matter what you do to it, you cant get your performance back. Once I had a pump so bad, and the car was very sluggish. I tried maxing the ALDA, and new injectors , just about everything.
Later on when I took the pump in for Calibration I found out it was Garbage. You need to get a new one. Check EBAY. Even a decent pump with a normal ALDA setting should be fine. You shouldnt have to turn the ALDA up that much.
I was told the new non sulfur diesel fuels kill todays IPs. Thats why I have two spare pumps.
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Old 05-09-2005, 04:24 PM
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Carrameow, I believe the MB pumps do not fail like some do due to low sulfur. Its not a problem let me assure you that is a scare tactic used to sell fuel additives. Using Redline Diesel Catalyst however isn't a bad idea because it raises the Cetane rating of today's crappy fuel and lubricates the IP.

Anyhow, as to another thing the '85 may have and greasup should check and be aware of in case he isn;t familiar with these cars, namely the possibility that it could have a trap oxidizer in it
If so, those tend to plug up and make the engine VERY sluggish. The remedy is take it to the dealer for possible replacement or upgrade. There are still people with low mileage '85 diesels that haven't had the factory campaign on these yet, I saw one last month! I wanted to buy that car it was so original like mint, and hardly broken in yet (sorry, I digress, but man it was so nice! but my wife would have me committed if I showed up with another 300D!)

Meanwhile back to the subject! greasup, you should check the boost sense line from the rear of the intake manifold over to the ALDA - it runs along the firewall, a hard plastic medium sized line - starts at the manifold ends at the ALDA with a switchover valve near the brake booster to interrrupt in the event of excessive boost pressure. This line collects crud and gets plugged up at the source end, then it fails to send pressure over to the ALDA, that is a very common problem that causes sulggishness and is the first thing one should check in a case like this.

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Old 05-09-2005, 11:52 PM
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Thanx for the good advice!

This problem reoccured when I had my oil and filter changed at a fast lube. When I pulled out of their parking lot the engine had about 50% of normal power. I watched a mercedes mechanic a month ago tear off the metal cap on top of the fuel injector pump on the back right of the engine and open the set screw. This helped at the time but I tried to adjust it out even more a couple of days ago with no response. Thanx again for your help.
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Old 05-09-2005, 11:53 PM
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Quote:
Originally Posted by greaseup
My engine runs smooth but very sluggish especially on take off. Turned the fuel injector pump set screw all the way open but no help. Changed all filters. Is this a vaccum leak or other problem?
Everyone has this problem sometime.

My Check list:
- Banjo fitting where boost tube connects to back of manifold plugged.
- Leaks around overpressure switch over valve on firewall.
- Leak in switch over valve - Try bypassing it.
- Alda may need tweaking - but this is not likely cause of problem unless it has failed.
- Fuel filter plugged up - Run some diesel purge through. Change main filter and small plastic filter. Sometimes, pick-up screen in tank gets blocked.
- Adjust valves
- Measure boost at highway speed (need gauge and connector)

Notice anything - No mention of Fuel injector pump
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Old 05-10-2005, 05:31 AM
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Unless Laethermang overrules me...

This problem reoccured when I had my oil and filter changed at a fast lube. When I pulled out of their parking lot the engine had about 50% of normal power. I watched a mercedes mechanic a month ago tear off the metal cap on top of the fuel injector pump on the back right of the engine and open the set screw. This helped at the time but I tried to adjust it out even more a couple of days ago with no response. Thanx again for your help.

The set screw on top of the injector pump was the ALDA. If the Mercedes mechanic adjusted the ALDA, he was smart enuff to check the Boost Line and Banjo fitting for plugging? I had an 87 300D where the boost line was plugged and I didnt lose 50% horsepower!
I'm not a guru, I'm a gorilla who asks questions from those who are smarter. I still kind of think the problem to be the fuel pump. Even if the white boost line gets plugged, you won't lose 50% horsepower. I went thru this, I changed injectors, filters,everything but in the end it was the pump.
You can buy a used one for $150.
It may be worthwhile to take your car to a good Mercedes independent in your area. Someone on the forum can recommend one to you.

Last edited by Carrameow; 05-10-2005 at 06:11 AM.
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  #9  
Old 05-10-2005, 10:13 PM
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Thumbs up Problem Solved!

Based on your advice I removed the banjo fitting and it was badly clogged. Power returned after a good cleaning. Thank you so much for your help. It's good to have Pro's available like you guys.

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