Engine vacuum pipe

[graham miller]

Can anyone help with vacuum pipe from the distributor on my 1980 6.9  I have two pipes coming from the distributor, two pipes from the switchover valve and two contoured hoses one with two vac holes and the other with one vac hole in it , there are two vac take off pipe, one is on the side of the throttle housing and the otheris on the front of the air guide housing. There is no EGR VALVE, on CHARCOAL CANISTER or AIR PUMP and no PURGE VALVE.  KIND REGARDS GRAHAM MILLER

[Big_Richard]

so you require the vacuum diagram for a euro specification 6.9 ?

[s class]

helpful information here :

Link

and here :

Link

and here :

Link

[koan]

Here's a link to scan of the 6.9 full emission set up:

(Click for big picture)

I suppose you just ignore what you haven't got.

The connections to both the electric c/o valve on firewall and the thermal valve on manifold must be as shown in the diagram. The left and right connections on firewall c/o valve can't be swapped, same with manifold thermal valve, angled connection is left one on the diagram.

Contoured hose at front of engine with one hole, the connection goes to control pressure regulator top or side - depends of what regulator end number is.

Contoured hose with two connections, one connection goes to control pressure regulator "other" connection. Second connection on this hose goes to firewall c/o valve.

Distributor retard connection to firewall c/o valve, advance connection to vertical connection on thermal valve via inline black/red/white vacuum delay valve, white side to distributor (and a tee-piece in my case for EGR). Angled connection of thermal valve connects to rear port of throttle housing, front port goes to charcoal canister - if you had one.

You don't mention the idle up valve, do you have one? if you do, small control port goes to manifold vacuum, not throttle vacuum.

koan

[WGB]

In essence - ON A EURO - the distributor can be both advanced and retarded by vacuum.

The advance comes directly from the manifold (under the throttle plate) via a red tube and connects to the advance side of the distributor.

The retard side is connected to the switchover valve to raise the idle when the airconditioning compressor is engaged.

Some of the connections are really only vents into controlled clean air.

Bill

[koan]

The advance comes directly from the manifold (under the throttle plate) via a red tube and connects to the advance side of the distributor.

I don't want to be pedantic and picky but your description is bit misleading WGB.

There are two sources of vacuum on a running engine.

One is all-the-time vacuum that is used for door locks, heater, brake booster and engine emission controls. This vacuum comes from the manifold somewhere and not the throttle body or carb.

Other source of vacuum and that used for ignition advance on most vehicles (my Hyundai heap being the only exception I've seen) comes from a port just above the closed throttle plate of the throttle body or carb.

Only after the throttle plate has moved above the vacuum port will vacuum advance be applied to the distributor.

Wrong vacuum to the distributor advance makes an engine respond to throttle in unexpected ways.

koan

[WGB]

Thank you for the "in-depth" Koan.

On an early Euro there are two connectors for the timing control of the distributor on the throttle body (up to chassis no 3385) one for advance and one for retard.
After chassis no 3385 (which should include your car Graham) there should be only a single vacuum port for advance with the retard being handled by a different vacuum connection to the warm up regulator.

Here is a picture of the US - full emission 1980 throttle body from a 450 with three ports and also a throttle valve switch.



I would imagine your 1980 Euro like both my 1979 Euro's 4.5 and 6.9 only has the one connection on the throttle body and it is not that easy to re-connect as it is deep down in the guts of the manifold.

When I went for my test drive with AMG69 I commented that the car was detonating slightly at low revs.

After purchasing the car I found the timing to be set at about 30 degrees advanced - it had been dynotuned for maximum performance.

It wasn't happy running on the "proper" 0 degrees until I found the "red" vacuum tube elbow wasn't connected to the throttle body.

What a difference in driveability when I pushed it on (with a lot of fiddling to get it on) - with the timing set at 0 degrees of course.

It is my understanding that the retard line from the warm up valve is there to raise the idle when the A-C compressor is pulled in and also to speed up the warmup by retarding ignition below a certain engine temp ?40 degrees C.


When my A-C system went flat my 6.9 would idle at up to 1100 revs whenever the A-C compressor clutch was pulled in.


Bill

[W116350SEL]

Sorry to steal the thread, but...

Anyone has a copy or knows where i can get a copy of M116 350 vacuum pipe diagram? Cheers.

Syed

[WGB]

What year and what market is the engine.

Bill

[W116350SEL]

What year and what market is the engine.

Bill

'78 350SEL Euro.

Cheers

Syed

[WGB]

I assume you are only referring to the engine vacuum connections. The chassis connections are well described in the workshop manual on-line here - just look under a 450 of the same year.

I do not have a euro 350 diagragm but here is a Euro 6.9 one showing the basic engine layout but not showing the distributor connections.

I cannot imagine a 350 one if it has K-jet will be greatly different.



Bill

[graham miller]

Thanks for all your in put, I know iam a bit thick but dose this mean the a/c change over valve pipe comes from the dist and gos back to the vac take off on the air guide kind regards GRAHAM MILLER

[WGB]

Hi Graham,

To put this to sleep once and for all I have removed the aircleaners of both my 1979 Euros - 4.5 and 6.9 and traced the lines to and from the distributor.

The two cars are identical except for the colours of the tubing.

The convention for naming the sides of components is as per sitting in the driving seat and looking forward - opposite of the view from the front of the bonnet.

The numbers attached to components are as per the diagram above.

1) Distributor advance vacuum comes from a single connector on the left side of the throttle body and connects to the advance side of the distributor vacuum control (outside connector). This tube should have originally been red.

2) Distributor retard vacuum is taken from the smaller connector on the rubber contour hose(18)which connects the auxillary air valve(10) to the idle speed distributor (21). This hose was probably originally a plain white or grey coloured hose (green on my 6.9) and runs directly to the yellow topped switchover valve on the firewall.

Euros have only one switchover valve on the firewall and it has two ports and an electrical connector.

The vacuum is supplied to the more central port adjacent to the electrical connector which is on the left side.

Coming from the other port on the right side is the return line which comes back and connects directly to the retard side (inside) of the distributor vacuum control.
On my 4.5 I believe this is the correct white colour with a violet line through it while my 6.9 has green with a yellow line through it.

The effect of the system is that when the switchover valve is not energised electrically the advance and retard sides of the diaphragm are in a controlled balance and at idle the timing is set for 0 degrees.

When the switchover valve is energised (at the same time as the compressor clutch) the vacuum line is sealed and the return line is vented to the atmosphere with the effect that the ignition is significantly advanced and the idle is increased.

And that is all there is to it - unless you have emission controls and then it gets much more complex.

Bill

[s class]

Thank you WGB.  That is the clearest, and most useful description I've seen.