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  #1  
Old 10-01-2013, 04:14 PM
Diesel forever
 
Join Date: Mar 2005
Location: Canada
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Loss of power, hilly gravel roads

I'm still a bit new to the 300TD (first turbo MB I've owned, after owning a 240D for many years). Overall I'm quite pleased with its acceleration and keeping up with traffic, compared to the 240D. At times, the acceleration when the turbo kicks in is quite nice (I'm not hard to please, after having driven the slug for many years)...

Anyway, all seems fine in the city, on the freeway, on the highway.

But when I drive to my cottage and hit the last 10 miles, if often feels like I've lost most of the power. Those 10 miles are curvy, hilly, and half of that is hard-packed gravel. For most of it I can't build up a lot of speed. When I hit a rise, no matter if I floor it, the turbo doesn't seem to kick in, and often I have to downshift halfway up the hill in order not to lose too much speed when I reach the crest. It has no problem picking up speed on the down side of the hill. The slowing down problem is worse on the gravel portion of the winding road.

When I leave the cottage, once I'm back on the highway, the turbo acceleration returns.

Does this sound normal and just something I have to contend with? Is the hilly last 10 miles just not allowing enough revs for the turbo to kick in and provide its boost?

I should point out that I replaced both primary and secondary fuel filters, to no avail. I've also checked linkage travel and it seems ok. Also removed banjo bolt and checked line, which wasn't plugged by cleaned it anyway. Is there something else I should check? (valve adjustment, turbo)

Confused...

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  #2  
Old 10-01-2013, 04:20 PM
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Join Date: May 2008
Location: Baltimore, MD
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Quote:
Originally Posted by rstl99 View Post
I'm still a bit new to the 300TD (first turbo MB I've owned, after owning a 240D for many years). Overall I'm quite pleased with its acceleration and keeping up with traffic, compared to the 240D. At times, the acceleration when the turbo kicks in is quite nice (I'm not hard to please, after having driven the slug for many years)...

Anyway, all seems fine in the city, on the freeway, on the highway.

But when I drive to my cottage and hit the last 10 miles, if often feels like I've lost most of the power. Those 10 miles are curvy, hilly, and half of that is hard-packed gravel. For most of it I can't build up a lot of speed. When I hit a rise, no matter if I floor it, the turbo doesn't seem to kick in, and often I have to downshift halfway up the hill in order not to lose too much speed when I reach the crest. It has no problem picking up speed on the down side of the hill. The slowing down problem is worse on the gravel portion of the winding road.

When I leave the cottage, once I'm back on the highway, the turbo acceleration returns.

Does this sound normal and just something I have to contend with? Is the hilly last 10 miles just not allowing enough revs for the turbo to kick in and provide its boost?

I should point out that I replaced both primary and secondary fuel filters, to no avail. Is there something else I should check? (valve adjustment, turbo)

Confused...
The turbo may not be spooling. Have you done any maintenance? Is the boost line from the back of the manifold to the ALDA clean on both ends?

It will slow down at low revs where you don't have the turbo spooled. What gear are you in when climbing? Maybe a downshift is what you need
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  #3  
Old 10-01-2013, 04:35 PM
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What's your normal speed on the gravel section? I'd try downshifting for that section. Maybe your kickdown switch isn't working.
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  #4  
Old 10-01-2013, 04:58 PM
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Just my 2 cents...

Quote:
Originally Posted by Simpler=Better View Post
The turbo may not be spooling....
It will slow down at low revs where you don't have the turbo spooled. What gear are you in when climbing? Maybe a downshift is what you need
Yeah, I'm betting it's a "gearing" issue, too high of a gear, turbo won't spool up at lower rev's, out of the power band, etc, etc.

I completely agree with the idea of down shift to a lower gear, see if that doesn't make a difference, I'm betting it does...
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  #5  
Old 10-01-2013, 06:02 PM
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I down shift for longer climbs anyway (rather than foot shifting). I think you'll find a lot prefer this "hold that gear" M.O.
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  #6  
Old 10-01-2013, 07:00 PM
Diesel forever
 
Join Date: Mar 2005
Location: Canada
Posts: 291
Thanks for all the replies. I think you're all right and it's probably a gearing issue, and not high enough revs to spool the turbo, and maybe kickdown switch is a little flakey (though it has worked once or twice when I took my foot off the accelerator then mashed it down). I ended up doing just what was recommended: shift into a lower gear, thereby increasing the revs. I used to do that all the time with the 240D auto, just to get around town, but didn't realize I would benefit from doing that with the massively higher HP 300TD! The guy I bought it from had it shipped to Europe at some point because he was posted in Germany for a few years. When it came time to ship it back home, some mechanic drove it to the docks with him inside, and this driver kept shifting the auto like there was no tomorrow, revving the heck out of the thing. He said everyone drove those old MB diesels like that over there. Maybe they were partly designed for that kind of manual-auto driving.

In any case, glad to hear that maybe all I have wrong is a partly faulty kickdown switch, and I'll keep down shifting in the steep climbs as I resorted to doing.

Funny that the effect is more prevalent on the gravel portion of the winding hilly road. Must have something to do with lower traction, laws of physics kicking in...

Thanks!!
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  #7  
Old 10-01-2013, 10:03 PM
Mad Scientist
 
Join Date: Dec 2012
Location: Oregon
Posts: 1,600
I had this same issue with my diesel conversion.

It was important for me to stop driving my MBZ diesel like the 8.3 and 5.9 Cummins(like in your Dodge) and 7.3 Fords I'd driven in the past, where 2500 RPMs was the redline. 2500 RPMs is the start of the power band on these MBZ motors. Go ahead and let it spin, that's what the motor is designed for.
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  #8  
Old 10-02-2013, 02:11 PM
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I live on hard gravel packed roads with allot of hills. It is normal for me to use 1 or 2 setting. The owners manual actually reccommends shifting them manually and not used the kick down swith. Mine is a 300SD '82
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Old 10-02-2013, 03:01 PM
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Quote:
Originally Posted by LNGfish View Post
I live on hard gravel packed roads with allot of hills. It is normal for me to use 1 or 2 setting. The owners manual actually reccommends shifting them manually and not used the kick down swith. Mine is a 300SD '82
x2 I drove mine like a manual every day. Just don't downshift while you're flooring it or you will prematurely wear the guts.
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  #10  
Old 10-03-2013, 01:45 AM
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Quote:
Originally Posted by Simpler=Better View Post
x2 I drove mine like a manual every day. Just don't downshift while you're flooring it or you will prematurely wear the guts.
Good tip for driving with a manual transmission too!

You don't need to "zing it"

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