efi intake plumbing
 

Perhaps dumb questions, but on my 1971 1800e, I am trying to sort the plumbing around the intake (I didn't take it apart).

Below the cold start throttle valve switch, there are two 1/2" open ports, one in front of the butterfly, one behind. I see pictures of cars with the oil breather hose running from a top port and I think out the front of the two lower ports toward the air intake. I also see there are cars that run this direct - any reason for this?

(I am not referring to the two side ports for the exhaust recirculating system).

On those that run the oil breather line direct, the top port is usually blocked. If I run direct, should either or both of the lower ports be blocked? Or are they moisture drains or something...?


Also - for the line running from the intake to the booster, I sometimes see a black union, looks like a plastic valve - something to adjust vacuum to the booster or something? required?


Thanks!
Kerry

I assume in the brake booster line there is a non return valve so the booster remains with the ¨power¨ for as long as possible.

Bosch / Mercedes CIS usually incorporates an air idle control valve which takes crankcase air and adds it to the mixture chamber behind the main throttle control plate (which is fixed to stay shut at idle but the engine still needs air)

I´m not sure how Volvo did this but I guess it can´t be too too different.

If someone can´t give you the answer you want post up some pictures of what you´ve got and I´m sure that´ll help.

Based on your description The 2 ports you refer to are for connection to the auxillary air valve that is attached to the head below the thermostat. It’s function is to increase idle when the vehicle is cold by allowing some extra air into the intake.

The plastic valve in the brake booster line is a one way valve.

There isn’t an EGR system on these cars.

There’s a Fuel Injection Fault Tracing Manual as well as an 1800E service manual available for download on this site.

http://volvo1800pictures.com/sweden/...on_misc_en.php

If you can post some pictures that would help.

Thanks re the Brake booster -

Regarding the intake - here is a picture of the two ports. Dead centre (you can see the other two hoses off to the right). My car seemed to have a hose from the air filter assembly with a sleeve that looks like it should fit, but doesn't slide in easily...

The line in question comes from the charcoal canister up front where the air filter is. Do you have a charcoal canister? They were often removed when they rusted out.

Ok, looked again, those 2 ports underneath and behind the charcoal canister line are blanked off. I don’t know why they are there. They appear to be internally connected to the AAV ports.

In any event my 71 1800E has the same arrangement, plugged from the factory and not used for anything.

Are yours open or plugged?

I will have to confirm that the rear one is a through opening - I could feel the opening behind the throttle, and on the bottom, but I didn't check to see if it was sealed in between. The one in front is open for sure.

I can see why, if the oil breather is plumbed to the air intake that the top and bottom front port would be opened, but I could not see a reason for the rear port behind the butterfly, seems counterintuitive to have a butterfly with an intentional leak behind it...

Actually, I can't really see why the oil breather needs to be plumbed at all - often they just have a filter on them to keep gunk from getting in.

Anyway, this is probably one of the least of my problems at the moment.

Thanks!

Ack - you were right c1800 - both of those "ports" were sealed.

The fitting on the short hose that I thought should plug in there must just have been a union for the hose to the oil breather - problem solved, thanks for the help,

Kerry

The oil breather is connected to the air intake from the air filter( factory) not one of these mystery ports. Or use a small filter directly on the breather tube as you suggested.

How is your idle, high?

One or two of the mystery ports, when open, would be allowing a lot of extra air into the intake, a vacuum leak.

Here’s a pic of mine, plumbed as per factory afaik, and a photo of the mystery ports.

Edit: Oops, just posted this before reading your latest response. Thought you’d like to see the pictures anyways.

That's a remarkably clean bay...
I'm currently tinkering toward confirming my engine is good - partly because my garage is pretty cold right now, but also because if the engine is bad, I'd rather start working on it now rather than waiting until after the body work is done... I have a bunch to do (including pulling the dash) - but the body isn't bad and I am hopeful I can be running this summer...

Most B20E and F Auxilliary Air Slide Valves eventually seize up, usually in the closed position and don't cause a problem other than difficult cold starting and idling until the engine is warm.

If the AAV seizes 'partially or fully open' you will have fast idling problems as the system is getting too much air when warm. These valves are no longer available from Bosch but can be refurbished by some specialists at enormous cost.

If seized in the open position the cure is to blank off the two hoses and/or ports on the valve which effectively creates a 'closed' valve, see paragraph one above. A later electric AAV from a Volvo 240 can be fitted with a bit of fiddling to mount a suitable bracket and connect a switched 12v supply, but to be honest it's not really worth the trouble.

My own 1800ES AAV has been seized for years, I blanked off the ports with rubber core plugs and apart from awkward starting in cold weather it's never been a problem. The important thing is that there are no air leaks in the system and that idling is properly adjusted using the butterfly adjusting screw/locknut and NOT the throttle cable stop.

Hope this helps?

Paul