|
|
|
#16
|
||||
|
||||
Quote:
John
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#17
|
||||
|
||||
Quote:
__________________
Dale http://i52.photobucket.com/albums/g1...MG_2277sig.jpg 1990 300D 2.5 Turbo -155k 2000 E430 - 103k 2014 Jeep Grand Cherokee Ecodiesel 4x4 - 11k 2014 VW Passat TDI SE - 7k Bro's Diesel 2006 E320 CDI - 128k Pop's Benz Pre-glow - A moment of silence in honor of Rudolph Diesel |
#18
|
|||
|
|||
Not quite...
There is some vacuum in the intake manifold or the air would get sucked into the engine for combustion on the engines without turbos... but you are are entirely correct that the lack of a throttle valve [as ther is in gas engines]... the lack of such a valve means there is much less vacuum [almost none at idel ]. IF you were to monitor the vacuum in the intake manifold of a naturally asperated diesel, you would NOT see the very distinct fluctuations as there are in a gas engine.
Possible Sidebar Reason - The 1930s/1940s generation of American automatic transmissions that MBZ copied in the 1930(s) when they first started building "slush trannies", well these were for gas engines and they were designed to shift based upon that same dramatically fluctuating intake manifold vacuum which is also a very good way to both measure the load on the engine and the "go" requests of the driver which needs to be communicated to the tranny. Thus the MBZ's engineer's ingenius design for a vacuum control system on their diesels which evolved over the years up through about 1985. Another Reason - This also allowed them to use basically the same trannies on GAS as well as Diesel engines. Much of the changes in the latter 1980(s) resulted from the engineers trying to appease the California State environmental "wackoes". If you don't believe me, take a look at the diagram for the 1985 California diesels at: http://www.peterschmid.com/vacuum/1977_1985/617_95/1985_cal.jpg. Thanks goodness they never made a "Federal" version of this system... at least I don't think they did?... in the SDL(s)??? Regards, |
#19
|
|||
|
|||
Quote:
|
#20
|
||||
|
||||
Quote:
__________________
http://farm8.staticflickr.com/7271/7...144c3fc1dc.jpg |
#21
|
|||
|
|||
Quote:
200D, 220D, and early 240D tuning guide. |
#22
|
|||
|
|||
Why do diesels need a vacuum pump?
I find it hard to believe where the POSTs on this THREAD have gone when the original question was a perfectly GOOD one that I'm sure many have wondered about !...
" Why do diesels need a vacuum pump ? " I'm out of here!Merry Christmas ! Regards, |
#23
|
|||
|
|||
I own an 84 190d ,the 4 cylinder runs great but the vacuum pump has long gone.When test driving it last week I kind of found this out by emergency needs,the guy selling it failed to let me know.Ive gotten use to breaking hard and can live with that for the mean time its the turning the car off that im trying to remedy .The line from the key to the IP has been guided via anothe rhose up to my console and when I need to shut it down i pull vacuum with my mity vac .Vacuum dosnt seem to happen except in very small amounts,the intake is were you can get it from a gasser.I was considering teeing into the line right before the windshield wiper reservior,that has to create vacuum ,how much is the question.The car performs well just looking for a cheaper fix for now.
|
#24
|
||||
|
||||
I knew our diesels needed a vacuum pump because the there was no vacuum generated (or not enough) on the intake manifold, but never really knew why This post answered the *why* in my opinion quite well. Anyway, what's the big deal with a little shop talk?
__________________
-justin 1987 300TD, 1987 300TD 2008 R32, 2000 Passat Wagon |
#25
|
|||
|
|||
Heres a ghetto fix for the shutoff that I discovered when looking at a 300D to buy - The guy had taken a length of wire, tied it to the shutoff lever on the injection pump, ran it around the front of the battery and into the passenger compartment through a grommet by the glove box. The he would hak on the wire to shut it down. I had to pass on that 300D, there were tons of "creative" repairs like that.
__________________
tgingrich '83 300TD 282k '83 300D 239k '82 300SD 204k DFW |
#26
|
||||
|
||||
rebuild kits for VPs are not terribly expensive. I think you can damage the brake booster if you drive much with out vacuum. also vacuum is needed for the automatic transmission to shift properly. door locks and engine shut off as well.
John
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#27
|
||||
|
||||
Quote:
Ford did exactly the same thing. Their automatics--C6 and others used engine vacuum to signal the tranny when to shift. When they installed a C6 tranny in a diesel pickup, they needed an "Transmission vacuum modulator" to convert the vacuum from the pump to a proper signal for the tranny. Its basically a variable bleed that reduces the vacuum to the tranny when the throttle is suddenly opened. Works well when it works. If it breaks, all shifts are like at WOT, meaning high in the engine's rev range and quite firm. Not many Ford-Mercedes similarity, but this is one.
__________________
1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags |
#28
|
||||
|
||||
ditto GM with their infamous 5.7L motors VP was driven off the cam, the pump looks like an HEI distributer without all the wires....
John
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread "as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do! My drivers: 1987 190D 2.5Turbo 1987 190D 2.5Turbo 1987 190D 2.5-5SPEED!!! 1987 300TD 1987 300TD 1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere! |
#29
|
|||
|
|||
Why do diesels have vacuum pumps? Well, not all diesels do have vacuum pumps but the ones that do generally have the pumps to provide vacuum to operate a myriad of control functions and accessories. Vacuum would seem to have been considered more reliable than electronics, etc. in engineering some vehicles from the not to distant past. MB liked to use vacuum for brakes, transmission control, emissions control, locks, ECC functions and shutting the engine off. Other manufacturers have used vacuum for the above stuff plus wipers, headlight doors, etc. RT
__________________
When all else fails, vote from the rooftops! 84' Mercedes Benz 300D Anthracite/black, 171K 03' Volkswagen Jetta TDI blue/black, 93K 93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K |
#30
|
|||
|
|||
Quote:
Regards, |
Bookmarks |
|
|