I think someone found this info in the Bosch IP manual. The IP has a centrifugal governor. It can easily reduce fuel flow when the accelerator position is at idle and the engine is 1000rpm or more the same way it cuts of fuel flow at 5000rpm with the accelerator floored.

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green 85 300SD 200K miles "Das Schlepper Frog" With a OM603 TBO360 turbo ( To be intercooled someday )( Kalifornistani emissons )
white 79 300SD 200K'ish miles "Farfegnugen" (RIP - cracked crank)
desert storm primer 63 T-bird "The Undead" (long term hibernation)

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Well, I might dispute the "can easily" part of that statement, if it actually proves to be true.

That would be quite a feat of engineering for a mechanical device. It's just a bunch of springs and levers cobbled together............nothing more.

I don't know what you guys are so worried about. I get 68mpg as per ebay.

Who cares about coasting?

I should be in bed now but you guys made me look this up:

"Believe it or not, at engine speeds above 1,200 rpm on a full downhill deceleration, you Mercedes's Bosch in-line pump injects no fuel at all into your engine!"

From page 153 of Chilton's Guide to Diesel Cars and Trucks, James Joseph, 1983.

It doesn't stike me as being a mechanically difficult feat to have a governor go to no fuel when the actual engine speed greatly exceeds the target engine speed.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Don't make it sound so amazing, it's 1960's technology.

yes but this is not what I am doing. "full downhill decelleration" is exactly what I dont want. by pushing in the clutch and coasting down hill I am eliminating the engine drag and reducing RPM to 500 for the duration of the coast. so far I have done this for 2 days and I can already see a little difference in my fuel guage position for tuesday. I will give a complete accounting once I empty the tank. It may or may not be worth the effort, but it is becoming habitual already. Optimistically I am thinking of it this way. My cost per mile is around $0.16. Every time I coast for .3 miles its like finding a nickel on the ground. Who wouldnt stop and pick up a nickel?

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1982 300CD Turbo (Otis, "ups & downs") parts for sale
2003 TJ with Hemi (to go anywhere, quickly) sold
2001 Excursion Powerstroke (to go dependably)
1970 Mustang 428SCJ (to go fast)
1962 Corvette LS1 (to go in style)
2001 Schwinn Grape Krate 10spd (if all else fails)

There is no "switch" to allow the governor to realize that it's at idle fuel. It must be done with linkages and cams and only activate when the fuel is at a dead idle.

If you were an engineer, you'd understand..........it's a difficult feat to accomplish..........and I'm still not convinced that it functions as advertised. The Chiltons manual is hardly the deFacto source.

The governor manual shows how it increases fuel at idle if the RPMs drop to compensate for loads (AC etc.) and decreases fuel when the RPMs raise to maintain a steady idle speed. It does not specifically state that no fuel is injected when engine braking, but the graphs of rack travel vs RPMs indicate that it is true. All it is is springs and flyweights in there...

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

I do put mine in neutral as well at stop lights. This is slightly better for your trans if you know you will be waiting awhile because the transmission slips a little while it's in gear. While your idling in gear, your creating heat letting it slip a little. Start your car, put it in gear for one minute in your driveway and then put it back in park and shut your engine off.

Now feel both of your transmission fluid cooling lines and one will be warmer than the other. This is helpful for figuring out how to install a separate trans cooler too. The warmer one will be your supply lione and the cooler one is the return!

Incorrect, it wears the transmission more to put it in neutral than to leave it in drive.

In N/P all the internals are moving freely and wearing against each other, in D the only things moving are the torque converter and pump.

Heat in D is not an issue, thats why there is a cooler in the radiator and you just proved my point.