EFI issue for CIS gurus - with pics

Scott R · Scott R's Garage

Ok, I'm tracking down an intake leak in my new EFI system. The way I understand CIS warm-up is that the AAR is open somewhat when cold and it allows and amount of air to pass through the intake to idle up a tad when cold. On my system I can extract air from the AAR line always, and a good amount of volume. This picture shows the two diaphragms AAV and I think a decel valve on my 1980 CIS system:

Regardless of how far the AAR is closed (it works BTW) I have a constant flow of air to the port near the CSV. So I removed the two pancakes in this photo:

The lower pancake is some sort of decel valve, and I can't pass air through it, it's sealed. The upper is the AAV and I can pass air though it all day long, it's open even under vacuum. Seeing as how this is open it leaves the AAR line open as well since it's a bypass for that line. Does anyone know if that's how this device s supposed to function?

I'm removing it either way, I just want to know how much farther to go in my troubleshooting.

tbitz · 08-08-2006, 09:17 PM

Scott,

Remove both and plug the aluminium hoses where they connect. If you don't plug the aluminium hose, you will get bypass air going into the engine and will have a very high idle RPM (engine may actually rev out of control since those holes are very big).

Cheers,

Tony

Mysterytrain · 08-09-2006, 08:20 AM

The AAR needs engine heat and 12 volts applied to it to get it to close. If it is working properly that should take 2 to 4 mins. You also need suction to get the opening of the AAR to seal. If you try to test it by blowing air into the openings it will leak.
The AAV pulls shut once the engine produces a vacuum. I've read that these can be tweeked. The AAV is the saucer shaped object with the sealed vacuum nipple. The other guy is the Decel valve.
http://members.rennlist.com/jimwms/CIS/CIShome.html

Scott R · Scott R's Garage

I'm pulling vaccum on the aav (saucer) using my desktop vacuum pump for AC. I can't ever get the AAV to close, where the decel is closed and does close. It's almost like the diaphram is ruptured for lack of a better term.

Elombard · 08-09-2006, 09:36 AM

Scott did you put 12 volts on it also? Will not close without that.

I thought the decel valve was the more upright egg looking thing on the other side rear of the intake set up? Maybe thats just on my 79.

Scott R · Scott R's Garage

Quote:

Originally posted by Elombard
Scott did you put 12 volts on it also? Will not close without that.

I thought the decel valve was the more upright egg looking thing on the other side rear of the intake set up? Maybe thats just on my 79.

Yea the AAR is closing when voltage is applied. I think you're correct in that 79' had the decel valve on the throttle body, I think in 80 they moved it to the pancake in my picture. It's me AAV pancake that I can't get to close, so it appears to bypass air around the AAR.

Elombard · 08-09-2006, 12:49 PM

I wonder if you could borrow a new pancake to try?

arcsine · 08-09-2006, 01:01 PM

Erik,
Something does not look right; the aux air valve should not have the smaller "niple" fitting but both the valves you show do. The decel valve should have one. I would be concerned that someone used a decel valve in place of an aux air valve. I don't know functionally if that would make a difference though.

In this pic, the aux air valve is second from right and decel is far right.

Scott R · Scott R's Garage

Quote:

Originally posted by arcsine
Erik,
Something does not look right; the aux air valve should not have the smaller "niple" fitting but both the valves you show do. The decel valve should have one. I would be concerned that someone used a decel valve in place of an aux air valve. I don't know functionally if that would make a difference though.

In this pic, the aux air valve is second from right and decel is far right.

You know, that has always bugged me, I have looked long and hard for a close up of another 80 to see if both should have a nipple.

safe · safe's Garage

Quote:

Originally posted by Scott R
I'm pulling vaccum on the aav (saucer) using my desktop vacuum pump for AC. I can't ever get the AAV to close, where the decel is closed and does close. It's almost like the diaphram is ruptured for lack of a better term.

Try to suck (with the mouth should be enough) on the vacuum side while holding a finger on the other side (so you can create a vacuum).
You should hear it close and then be able to remove your finger and the valve should stay closed.

Scott R · Scott R's Garage

Quote:

Originally posted by safe
Try to suck (with the mouth should be enough) on the vacuum side while holding a finger on the other side (so you can create a vacuum).
You should hear it close and then be able to remove your finger and the valve should stay closed.

I'll try that, thanks.

Scott R · Scott R's Garage

Quote:

Originally posted by safe
Try to suck (with the mouth should be enough) on the vacuum side while holding a finger on the other side (so you can create a vacuum).
You should hear it close and then be able to remove your finger and the valve should stay closed.

OK, that works. Now I had no vacuum source on the AAV after my EFI conversion, figured it was an unused device at that point. As I guessed it appears that this would cause a leak.

arcsine · 08-09-2006, 02:22 PM

going here: http://members.rennlist.com/jimwms/CIS/CIShome.html will give you the low down on all things CIS.

The pre-80 SC's used the silver decel valve (shown on the far left) and the post used the gold one. All used the same aux air valve and should be nipple-less (which even hurts to write).

Scott R · Scott R's Garage

Quote:

Originally posted by arcsine
going here: http://members.rennlist.com/jimwms/CIS/CIShome.html will give you the low down on all things CIS.

The pre-80 SC's used the silver decel valve (shown on the far left) and the post used the gold one. All used the same aux air valve and should be nipple-less (which even hurts to write).

LOL, my CIS was so hacked from the get go, this does not suprise me at all.

tbitz · 08-09-2006, 02:35 PM

Scott,

For EFI you really don't need the AAV (to avoid confusion this is the part that aids in starting engine by allowing extra air while cranking). Precise fuel metering of EFI while cranking renders this part useless. My car starts without pressing the throttle cold/hot every time.

It looks like you have two decel valves anyway. If the decel valve works, I guess you can leave it in. It should not allow bypass air during idle if it works properly. The other end used to go to the CIS boot, (which you don't have anymore), so you could just find a small air breather filter and fit it. You'll have to find a seperate vacuum source for it because you DON"T want to hook it up with the ECU vacuum hose.

Cheers,

Tony

Scott R · Scott R's Garage

Quote:

Originally posted by tbitz
Scott,

For EFI you really don't need the AAV (to avoid confusion this is the part that aids in starting engine by allowing extra air while cranking). Precise fuel metering of EFI while cranking renders this part useless. My car starts without pressing the throttle cold/hot every time.

It looks like you have two decel valves anyway. If the decel valve works, I guess you can leave it in. It should not allow bypass air during idle if it works properly. The other end used to go to the CIS boot, (which you don't have anymore), so you could just find a small air breather filter and fit it. You'll have to find a seperate vacuum source for it because you DON"T want to hook it up with the ECU vacuum hose.

Cheers,

Tony

I did actually keep the CIS air boot, I was/am going for the "stealth look" right now, that may change at this point however. I'm going to delete both and plug all four openings, that should only allow the AAR to function.