Author Topic: vac lines connected properly (retard valve)  (Read 145 times)

irvine

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vac lines connected properly (retard valve)
« on: 10 May 2019, 12:54 AM »
Hey team, I've got a quick question that been bugging me, my 280se has never ran properly and 2 vacuum lines in the engine bay have always had me thinking. Are they the correct way round???

the motor in question is a 280se d-jet.

And the 2 vac lines in question, one comes from a nipple on top of the throttle body and goes direct to a little bell shaped valve mounted on the back of the engine bay.
Its plugged into the outside nipple.
The other vac line then comes from the middle nipple and goes direct to the retard diaphrame mounted on the side of the distributor.


Are these lines connected up properly???

below are pics to help.

this is the bell shaped valve:
W116 by Neil Irvine, on Flickr

connection to throttle body:
W116 by Neil Irvine, on Flickr

connection at distributor:
W116 by Neil Irvine, on Flickr



huge thanks as always,
neil.

goldacre

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Re: vac lines connected properly (retard valve)
« Reply #1 on: 10 May 2019, 01:24 AM »
Hi Neil, sticking my neck out here  :-\ but on my K Jet 450 the firewall mounted valve kicks in when the AC compressor turns on? Pretty sure it retards the ignition for that function but was a while ago I was sussing it out.

Albeit you have a D Jet so uses more valves etc to operate the fuel injection?

G

12/1979 450 SEL 136K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)

Randys01

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Re: vac lines connected properly (retard valve)
« Reply #2 on: 10 May 2019, 03:21 AM »
If there is a connection issue, it will be the lines going into the little bell unit. They can be easily swapped over by mistake.
Now this is a bush fix.  If you have a vacuum pump, then you can do it in style. otherwise......
To test: start the engine ;remove the line from the retard unit to the dizzy.
Put a bit of spit  ::)over the valve port. It should remain unaffected... turn on the aircon. Place a bit more spit over the port..if it is sucked in, the connection orientation is correct and everyone is working.
If no result, swap the lines over on the unit and repeat. Once you have got suction estab on the correct line ..only when the a/con is selected. ..mark the lines for future reference and then...
turn every thing off.........join a hose to the dizzy retard port..take the diz cap off and suck on the line.If you can see the base plate move a bit, then all is good. If it doesn't move then you have an issue with the dizzy.

It's a bit of a weird notion but the valve works to keep the dizzy in a state of constant retard at idle-ish. When the addit load of the aircon is selected the engine needs a bit of a step up.  In this 70's inspired design, the valve shuts off the vacuum and the dizzy advances a bit.

In carby engines of the same era,  a vacuum diapragm on the carb would trigger a little arm which would turn the throttle butterfly a tad.
In modern cars, idle step up is managed by the ECU which tells the ICM to ramp her up.

K jet and D jet use the same principle and valve etc......the vacuum source is just a bit different.

Randys01

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Re: vac lines connected properly (retard valve)
« Reply #3 on: 10 May 2019, 03:46 AM »
Erratum:
Sorry folks......
Replace below with this Version 2.

If there is a connection issue, it will be the lines going into the little bell unit. They can be easily swapped over by mistake.
Now this is a bush fix.  If you have a vacuum pump, then you can do it in style. otherwise......
To test: start the engine ;Aircon off...remove the line from the retard unit to the dizzy.
Put a bit of spit over the valve port. It should be sucked in... turn on the aircon. Place a bit more spit over the port..it should remain static.

If no result, swap the lines over on the unit and repeat. Once you have got suction estab on the correct line ..only when the a/con is de-selected. ..mark the lines for future reference and then...
Engine off...........join a hose to the dizzy retard port..take the diz cap off and suck on the line. If you can see the base plate move a bit, then all is good. If it doesn't move then you have an issue with the dizzy.

It's a bit of a weird notion but the valve works to keep the dizzy in a state of constant retard at idle-ish. When the addit load of the aircon is selected the engine needs a bit of a step up.  In this 70's inspired design, the valve shuts off the vacuum and the dizzy advances a bit.

In carby engines of the same era,  a vacuum diapragm on the carb would trigger a little arm which would turn the throttle butterfly a tad.
In modern cars, idle step up is managed by the ECU which tells the ICM to ramp her up.

K jet and D jet use the same principle and valve etc......the vacuum source is just a bit different.

irvine

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Re: vac lines connected properly (retard valve)
« Reply #4 on: 10 May 2019, 03:46 AM »
Mate your a legend for that description,
I’ll give it a go and get back to you.

Big thanks.
Neil.

Randys01

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Re: vac lines connected properly (retard valve)
« Reply #5 on: 10 May 2019, 04:40 PM »
Neil  The port closest to the centreline of the car accepts the vacuum source. My little earlier parable helps you test that the sytem is working once correctly hitched up.

irvine

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Re: vac lines connected properly (retard valve)
« Reply #6 on: 10 May 2019, 05:24 PM »
Randy mate your a legend, and the bush fix method is a total winner. I’ll give it a go today once I’ve had my coffee.

Neil.

irvine

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Re: vac lines connected properly (retard valve)
« Reply #7 on: 10 May 2019, 07:02 PM »
Ok I give it a go.
I pulled the line coming off the dizzy and with the ac off it was sucking. When I switched the ac on it stoped sucking.

I swooped the vac lines round at the valve and it done the same thing  ???
I checked the dizzy end with the ac off and it sucked, when I turned the ac on it stopped.

Randys01

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Re: vac lines connected properly (retard valve)
« Reply #8 on: 11 May 2019, 11:55 PM »
"I pulled the line coming off the dizzy and with the ac off it was sucking. When I switched the ac on it stoped sucking."

That is correct. Go no further.


" The port closest to the centreline of the car accepts the vacuum source"

Is the vacuum source line connected to valve via the port closest to the centreline of the vehicle.?  That is, in your photo the braided hose is the one that should be connected to the vacuum source.

When you swapped the lines over, it should have made a difference. ???WT... The valve is not bio directional.

Ok. so we note the idle with aircon off. We turn the aircon on.Do you notice if the revs rise, remains the same or slows down?
It should remain as near as damn it the same .
If the engine clearly feels the load of the aircon, your valve is screwy or the retard in the dizzy is playing up.
Finally unclip the power source to the valve. work the a/con on and off. You should notice the engine lugs a bit when the aircon is selected.