.When I attach my MIty-Vac to the distributor and apply vacuum, rpm goes up.

When I attach vacuum lines from changeover switch to throttle body and distributor as illustrated and activate switch, no noticeable or actual increase in idle while sitting with no load (a/c off).

With switch hooked up to a/c compressor and turned on, at idle of 1000rpm in park, there is a drop in idle, but does not die and hangs at 700-750 rpm.

Vacuum from throttle body is less than 2psi at idle and distributor seem to need 7-10psi to increase....as I applied such to distributor with Mity-Vac.

I am still a little sketchy on the workings here. Here is my assumption:When engine is at idle, little vacuum is present, so virtually no increase in idle will take place through distributor, when manually activating changeover switch. With switch connected to compressor and activated, additional load is put on motor,vac increases a bit (due to load ?), idle increases (not felt) but enough to sustain load put on motor and keep from shutting off ?

Curiously, I cranked up my Dodge, drove around the block to warm up and while at a stop sign at idle, activated a/c and watched rpm drop 150-200 on it.Do you think I am on the right thinking path ?

My G has the factory a/c and EPC shows an "Idling Adjustment Valve" that should be somewhere in this setup...however, you pull that part number up (A000 094 12 65) and only shows applicable to the M102 cross country vehicle and M110 powered sedans for Japan and South Africa. Kind of bizarre.

I will leave connected as such and see what happens for awhile. I am just happy I was able to put everything back together in the intake side without any troubles or leaks...it was actually quite rewarding and fun.

Mike

P.S. Sorry about the funky paragraphing, something happened that put everything as one paragraph so I had to edit html.

Edited by DesertStar 7/5/2008 6:38 PM

Thanks Bernie, another big help. From what you have posted, most everything is coming together now. My new hoses, by which I thought were the right ones for my truck are probably not. My old hoses, which I thought have been altered are/were correct. Yikes...you can see this pretty much mirrors that of what the W107 diagram I posted as well as what Hipine and Bram have tried to hammer in my hard head..

I posted a photo of my old hoses and drew a Monty Python looking diagram of the setup I believe now to be the correct....really this time. When I got my G none of this was hooked up and was glued/plugged and leaking.

(flyingcircus1234 [1024x768].jpg)

flyingcircus1234 [1024x768].jpg (199KB - 8 downloads)

Thanks Bram for your support...as always. I am not unhappy as I learned quite a bit in this venture. My confidence is up and I feel I can replace those hoses within 2 hours easy. The EPC shows multiple hoses, I had to choose what I thought was correct based on my observations from underneath and really not knowing the system. I also wanted to purchase ahead of time so I can replace with minimal downtime.

Word to the wise, be smart and verify which hoses you actually have, before you order, as there are many configurations based on what your G is equipped with. Sadly, the EPC did not provide clear "pictures" of the related parts.

I do not use the a/c in stop and go traffic and slow off-road trails, I generally use on highways and higher speeds over 35mph, so should not be a short term problem. Come to think of it, other than a slower idle with a/c on, it really has not posed a problem since I owned it with it not hooked up. It sure is nice to have things the way they were meant to be though.

One idea that could be derived from this thread, is if you are considering removing the intake and "cleaning things up", the addition of the hoses that have the ports for the idle speed increase may be of interest for those that want to add a winch,on-board compressor etc. One could rig up a switch inside and manually control the changeover valve to bump up idle a bit.

Bernie, when at idle in your driveway, and you activate a/c, does your rpms actually go up or does it pretty much keep the idle the same but under load ? I heard something like 80rpm increase but it would seem to need more of a bump as without the device the a/c causes my idle to lose 150-200rpm, but still hovering at 650-700.

Mike

P.S. I will take a raincheck Bernie, until you get your G back together, unless you know from memory. 

Is that anything like elbow grease? In all seriousness, I wondered if something might be stuck in the vacuum through the distributor - is cleaning and re greasing a difficult job?

Thx ... I'll give it a look! 

Now that's more like it!  Looks like you have it now.

Just one comment, Mike.  This may go without saying for someone with your experience, but for others following th thread later, consider this.

On that 3-port electrical vacuum swtiching valve.  It has three ports, call them A, B, and C.  When there's NO power to it you'll find A open to C and B blocked.  When you put power to it, you'll find A open to B, and C blocked.  If you do the power on/off experiment and label the ports as above by how they perform with power on and off, then you'll want to hook port A to the AC valve, port B to the vacuum supply from the lower manifold, and C to atmosphere (a good idea to put a little filter over that one to keep spiders and dirt out!)  Also a good idea to mount that switch high in the engein compartment to keep it out of the dust and mud for the same reasons.

The idea is that you want to vent the AC high idle pot to atmosphere when the switching valve is off so it returns quickly to it's closed position, and you DON'T want to vent the vacuum supply ever.

-Dave G.

Dave, while I have your ear. Concerning Karl's comments on the distributor, at what vacuum value should it start advancing at ?  Maybe a quick lesson in the workings are in order here.  Do I have this right:

At idle there is little vacuum = no advance.

Increasing idle yields more vacuum = more advance

Gwagen approaching/ ascending a long hill or grade gives even more vacuum (under load) = max advance

 What is tell-tale sign of the advance not working properly...especially on an already sluggish motor.

Mike 

Maybe a new thread would be in order, but the simple approach is kind of the opposite of what you describe.  The engine has its greatest vacuum at idle.  The throttle plate is closed and the engine pulling against it is what "makes" vacuum.  As soon as you open the throttle you have less vacuum because air starts flowing into the engine past the throttle plate.  Vacuum advance gets less and less as throttle opening increases.  Some cars also have a centrifugal advance that takes over at some point to advance timing with RPM increase, but in the G that function is most likely done by the spark box reading RPM from the crank sensor.

Some other things that can effect how an individual system works are where the vacuum is ported to and from.  If you see no vacuum on the yellow line at idle, it means the vacuum to that side of the pot on the dizzy is ported from above the throtle plate.  In this case you'd see vacuum on that line jump up as you come off idle, and then drop as the plate opens farther and farther.  Vacuum lines going to BOTH sides of the vacuum pot on the dizzy means that the system is using that system to retard the timing as well as to advance it under various conditions.

Our Gs were made during the sort of "dark ages" of engine control when they were trying to perform some alchemy and bring the engine under finer and finer control using old time methods.  They pretty quickly figured out that they were beyond the capabliities of vacuum lines and temperature sensors to achieve the control they desired and moved into computer control of spark timing, EGR position, and fuel delivery, among other things.  In order to figure out just how the system on the G works (beyond the basics above), the best thing would be to have a description from a workshop manual.  I don't see anything about it in the G manuals I have.  Maybe an M110 in a car from about '79 would be close.

-Dave G.

Thanks Dave. I did have it backwards and found my mistake while reading the Bosch Management book. Your explanation is more clear, however. I also reviewed the M110 configurations for vacuum on the sedans....geez there are quite a few.

Mike

Glad to hear it!  By 1980 the days of being able to intuitively understand engine management systems from a quick look and a basic understanding of things were fast departing.  The computerization of things was a definite improvement over those convoluted electro-mechanical means, IMHO.  At least when I opened the hood ans saw only black boxes, sensors, and motors I KNEW I didn't stand a chance of knowing how it worked without a book and could save myself the "figure this out" time.

All the best,

-Dave G.

Drew, from the photo (on this message number that I am replying to) it looks like your distributor has two vacuum lines going to it, while mine has the one. You show that yellow line going back to distributor...like on the bottom ? Yours being older, probably has vac ports for both retarding and advancing distributor for various conditions. Interesting, I did not catch that bit as I was troubleshooting mine. Hipine, for curiousity, did your dizzy have two vac ports ?

Mike

P.S. Karl, my G is doing fine, keeping it inside the garage away from all that California smoke.