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  #1  
Old 10-13-2004, 12:45 PM
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My '77 240D has no butterfly in the air

intake(can that be called "intake manifold" since the fuel is injected?) & the '83 parts car has a butterfly. The same is true for the plastic unit on top of the valve cover('83 has it, '77 does not). Will someone please clue a newbie diesel owner in....

One more - why do they have a pump for vacuum when I am cautioned to not try to stop a run away by placing my hand over the air intake(I read that you can lose body parts!).

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  #2  
Old 10-13-2004, 12:50 PM
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Can't a runaway engine be stopped by the stop lever?
-Joe
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  #3  
Old 10-13-2004, 01:14 PM
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A normally aspirated diesel has only a little vacuum and a turbo frequently has positive pressure in the intake. The amount of vacuum necessary for existing vacuum operated devices is not available off the intake, hence the pump. Gasoline engines develop significant vacuum below the throttle plate in a carburated engine. Ever watch vacuum operated wipers slow down when the car is climbing a hill? Throttle open, low vacuum and you are at least as old as me. A runaway diesel isn't stopped by the stop lever because it ran away in the first place because something isn't right in the mechanical feedback mechanism in the injection pump. It can be stopped by THOROUGHLY blocking the air, which isn't always a sure bet depending on how its executed, using a fire extinguisher in the intake (a carbon dioxide one is clean and will displace the oxygen necessary for running) or removing the high pressure fuel at the injectors, by loosening or cutting the lines. Some have mentioned the possibility of an engine with a lot of blowby running away by aspirating crankcase oil too.
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Old 10-13-2004, 01:32 PM
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I doubt I am as old as you, but I have seen vacuum-operated wipers on Dad's 56 International pickup. Used to annoy the hell out of me when I drove it in the rain. Took him a long time to get it through my head why they slowed down like that.
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Old 10-13-2004, 03:40 PM
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The plastic box on top of the 83 is related to emissions equipment that the 77 doesn't have. I'm not sure about the butterfly, but suspect the same.
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  #6  
Old 10-13-2004, 07:38 PM
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Its the EGR OM616 style...
The exhaust goes from a hole/port in the exh manifold, through a vaccuum controlled valve (I think) through a tube through that butterfly and into the intake stream, decreasing emissions (and power...just read here a while to see what most think about functional EGRs...).
Wedge that butterfly shut and decrease youe egr flow. The black plastic box is either vacuum switching for the auto-trans (if you have one) and/or the vacuum switiching that disables egr at idle and full throttle.

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  #7  
Old 10-14-2004, 11:17 AM
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Thanks for the replys - and Pete, I'm old enough

to even remember the hand lever on those wipers that could be used to give them a boost if needed....
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  #8  
Old 10-14-2004, 05:00 PM
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Quote:
Originally Posted by trontek
to even remember the hand lever on those wipers that could be used to give them a boost if needed....
Seem's like my '31 Ford had those. I got stopped in San Diego, CA by a city cop one night backing up a long steep hill. The guy give me two tickets, but they got thrown out by the judge.

Anyone know why I was backing up the hill?
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Old 10-14-2004, 05:28 PM
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About out of fuel?

......
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  #10  
Old 10-14-2004, 05:42 PM
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Quote:
Originally Posted by trontek
......
Nope.
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  #11  
Old 10-14-2004, 06:25 PM
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There had been so much rain that the unpaved road was

so muddy the A would not go up in forward gear?
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  #12  
Old 10-14-2004, 06:42 PM
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Quote:
Originally Posted by trontek
so muddy the A would not go up in forward gear?
Naw, not it. :p Come on there has to be someone out their in MB land.
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  #13  
Old 10-14-2004, 07:15 PM
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Answers

Quote:
Originally Posted by trontek
One more - why do they have a pump for vacuum when I am cautioned to not try to stop a run away by placing my hand over the air intake(I read that you can lose body parts!).
Law of physics can kill.
The run away is over revving, sheer momentum will keep it cycling as a giant multi cylinder vacuum pump, this is one of the few times when it can build hard vacuum in the intake manifold, hard enough to suck your blood through skin and in some diesels, break the bones in your hand, followed by sucking it in.
Here is an article I wrote.
Run away diesel, why does it happen?

Note:
A dry chemical fire extinguisher does a wonderful job of junking a run away diesel…
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  #14  
Old 10-14-2004, 11:47 PM
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Quote:
Law of physics can kill.
Hunter is that your answer for the backwards up the hill in Model A Ford?
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  #15  
Old 10-14-2004, 11:56 PM
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I believe some 240s had mechanical governors instead of vacuum governors, so they won't have a butterfly in the intake. If there is a vacuum line to the back of the IP, you have a vacuum governor. If not, it's mechanical and there won't be a butterfly in there.

Don't mistake the vacuum throttle for the anti-backrunning plate.

As for stopping a runaway engine, the safe (although messy) way is to loosen the injector lines. You can also discharge a CO2 fire extinguisher into the intake. The main reason not to use your hand is that the suction will cause serious bruising and might even rupture the skin. On turbos, you would have to remove the air filter housing and cover the turbo intake (else too much air gets in and it won't stop), and the turbo will cheerfully munch off most of your hand it if touches the turbine. Not funny.

Peter

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