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Join Date: May 2014
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1977 2.7 911 vacuum advance question

I am still having trouble getting the CIS adjusted properly but on the other hand I just found that the hose to the vacuum advance on the distributor is connected but there is a rubber plug somebody put in it. I took the plug out of the line and pushed it back on to the vacuum advance and it makes no difference. I just bought the car 3 months ago. It was running absolutely great until the weather turned cold at which time I set about adjusting the fuel mixture with the 3mm wrench. The aux air reg. had also seized up so I sprayed WD40 into it, reinstalled the hose and went about adjusting the fuel. I've gone richer and leaner both but it still cuts out when I get on it. I know...I'm trying to explain 2 different things here. Just don't know what to do next. It was running stellar just before the cold set in and the AAR seized up.

Thanks
Old 12-31-2017, 01:02 PM
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Ampex,

The vacuum line will slightly change the timing at idle, but you may not notice it.


The mixture screw is very sensitive - you don't have to move it much. How far have you turned this screw?

Do you have fuel pressure gauges? If not, they are a good investment and will be necessary to diagnose poor running.
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1975 911s and 2012 Range Rover Sport HSE
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Old 12-31-2017, 01:52 PM
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The ‘77 distributors are vacuum retard. I don’t notice a difference with it hooked up or blocked. Mine had a red cover/ plug fitting on the port that the hose hooked up to blocking vacuum when I bought it. Ran it that way for twenty years until I noticed it and removed.

Like I said, no difference in my experience.
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Rutager West

1977 911S Targa Chocolate Brown
Old 12-31-2017, 02:17 PM
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The AAR will put a “ton” of unmetered air into the system if it isn’t closing once the engine warms up. You could try to block and cap the hose and valve once the car warms up and see if it isn’t closing.
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Rutager West

1977 911S Targa Chocolate Brown
Old 12-31-2017, 02:22 PM
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Since your running issues started with cooler weather, I would get a CIS gauge set and check, warm up regulator pressures. With time the regulators become too lean. Many posts on this issue. Rob
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Nope.......

Quote:
Originally Posted by rwest View Post
The AAR will put a “ton” of unmetered air into the system if it isn’t closing once the engine warms up. You could try to block and cap the hose and valve once the car warms up and see if it isn’t closing.

RWest,

The air passing through AAR is all metered unless you have a hole or crack on the vacuum line.

Tony
Old 12-31-2017, 02:39 PM
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Quote:
Originally Posted by boyt911sc View Post
RWest,

The air passing through AAR is all metered unless you have a hole or crack on the vacuum line.

Tony
Yes, you’re correct, my error.

It does get the air off the boot after the fuel distributor, so metered; not sure where my brain was earlier.
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Old 12-31-2017, 03:38 PM
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Quote:
Originally Posted by ampex351 View Post
I am still having trouble getting the CIS adjusted properly but on the other hand I just found that the hose to the vacuum advance on the distributor is connected but there is a rubber plug somebody put in it. I took the plug out of the line and pushed it back on to the vacuum advance and it makes no difference. I just bought the car 3 months ago. It was running absolutely great until the weather turned cold at which time I set about adjusting the fuel mixture with the 3mm wrench. The aux air reg. had also seized up so I sprayed WD40 into it, reinstalled the hose and went about adjusting the fuel. I've gone richer and leaner both but it still cuts out when I get on it. I know...I'm trying to explain 2 different things here. Just don't know what to do next. It was running stellar just before the cold set in and the AAR seized up.

Thanks
'77 was the first year for the Warm up regulator thermo valve, make sure that this is working right first


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Old 12-31-2017, 04:14 PM
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thermo valve and vacuum line form WUR to throttle body.
make sure the is vacuum at the WUR at IDLE. if not, it will not accelerate very if at all.
you can bypass the TTV, but it is very nice to have in very a vary cold climate.

for the dist.

find a vac hose with vac on it at idle. connect it to each of the ports to determine which one is advance and which is retard.
vac retard has vac ONLY at idle.
vac advance ONLY has vac above idle.
you can look at the TB and see which ports are above and below the plate, when closed.
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Old 01-03-2018, 07:52 AM
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A 77 only uses vacuum retard to meet idle emissions. There is no advance connection until 1978 which was the first advance
Bruce
Old 01-03-2018, 08:01 AM
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