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1984 300TD
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123 Posts
Discussion Starter #1
I installed a low miles 617 and 4 speed stick in a 300TDT wagon. This motor does not return to idle immediately .... maybe 10 to 15 seconds to drop from 2500 to 1000 or 1500 RPM... making the usual rhythm of driving stick real strange in fact not possible.... since with a stick it is usual to allow the motor to slow the car frequently. My 240D stick has slow return to idle until its warm... I think its built that way, has always done so from day one with a Metric Motors long block.

Smokes a lot too though that is improving after a few initial short trips after adding Rislone engine improver.

I suspect diesel IP is the culpret... the linkage is from the automatic that was in the car originally and it operates normally, no hangups or whatever.

Anyone got any experience with this??

Thanks if advance....
 

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1984 300D
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5,070 Posts
Is this also happening when the Car is not moving and your rev the Engine or does it only happen when the Car is on the road.
 

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Premium Member
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496 Posts
My first thought would be gummy throttle linkages, like lithium grease with extra gunk collected... but I think you're past that in the lookup procedure. :)

Dave aka Ghan
 

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1984 300TD
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123 Posts
Discussion Starter #4 (Edited)
RPM "floats" ie does not drop to idle normally

It does so both when stationary and while at speed .... it seems like the momentum of the car makes it worse though ie it drops quicker while not moving, but still not immediately as it should. I live at the top of a long partly steep grade .... need the brakes very little while driving my 240D down the hill after first start of the day.

It's so noticeable at speed, it requires more use of brakes.

Also, it will not idle when stone cold without a foot on the accelerator pedal. Then it searches for idle before it is fully warmed up.

I bought MM oil assuming I'd need the MM 2 week routine per 300Dmans accounts, before I did this compression test:
1 400
2 400
3 420
4 390
5 380

That #3 seemed odd but it started during the test with #4 and 5 still had glow plug in and connected ... I clamped ip pump in stop position, apparently that does not work to stop fuel though that does shut it down normally when its running.

With compression like that is still smokes too much ...compression rings OK, oil rings not?? The smoke improved considerably after getting the IP timing right at 24BTDC. NOw the smoke seems blue not black like it was with timing at 100BTDC ... and it runs more or less normal except for "floating" rpm.

The control linkage is not hung up, moves freely into idle position.


Thanks again in advance.
 

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'77 6.9, 74 240D, 96 Ram 5.9L Cummins
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2,654 Posts
Is the engine slow to return to idle even if it's in neutral, E-brake on and you blip the throttle linkage from the engine bay? Video post maybe?
 

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1984 300TD
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123 Posts
Discussion Starter #6
Yes, stationary in neutral it does not immediately drop in rpm to idle. It "floats" .... slowly decreasing rpm to normal idle. While at speed the momentum of the car seems to make it worse, as though it would never decrease in speed just by the compression of the engine if one was going down even a gentle downhill incline.

Reving it from under the hood is the same, elevate rpm for a short time then release the linkage, which operates easily and returns immediately to the idle position, the engine returns to idle slowly.

Its getting a MMoil soak of suspected stuck oil rings now. When its running again I can quantify the problem... approx 5 seconds to decrease from 2000 rpm to 1000 rpm while freely reving in neutral.... no video available....

thanks
 

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Premium Member
99 SLK230 Kompressor, 5 Speed Manual
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1,117 Posts
In the course of all this work was the injection pump removed or messed with in any way? Particulary, was the governor touched?
 

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1984 300TD
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123 Posts
Discussion Starter #8 (Edited)
IP timing was dialed in to 24BTDC. It was not removed. A local guy who is the "go to" guy locally that rebuilds these IP pumps (Pacific Fuel Injection, S. San Francisco, CA) suggested turn rack damper out half a turn to see if that makes a difference regarding return to idle problems. He refers to the 12mm and 14mm concentric hex bolts at rear of ip and below the vacuum stop mechanism toward the rear and top of ip pump as a mechanism that applies variable friction to the "governor", I gather many refer to this as the rack damper?? True??

A local IP rebuilder Gus suggested turn governor damper out one half turn, which did not improve return to idle issue. Half a turn in made searching idle worse ... induced loping ... return to original position returned function to as before.

This engine smokes too much yet has good compression.

It will not idle while stone cold. As it begins to warm up it will idle without my foot on accelerator but searches. As it continues to warm it smoothes idle to apparent normal.

Thanks
 
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