3.3 Vacuum nightmare..

[myle860]

So Im getting ready to pull my hear our out or just take it to a shop. But Seems I cant get the vacuum system right. It seems like the distubitor and the egr vavle almost always have vacuum. I tested the vacuum switch and it good...Here is the map im working off of. The other wierd thing im fighting is the coke never seems to want top open all the way when it warms up...

[reflist][/reflist]

[myle860]

Now that the sun is out here is what I have going on.

[xctasy]

This'll help ya...

I want you to know I've never, ever had a problem with any of the 1981 3.3 Mustangs vac fittings, carb operation, ignition, and that's because I always detail what parts go to what by taking videos and camera shots. When some Alan Beresford B'Stard has being playing with it, then its like restoring democracy to a banana republic...it'll fight you every step of the way.

My VECI is


E1 BE 9C485 CA, DCK



Mine has Air Conditioning, so it has the throttle kicker adjustment line.

Yours might not have that.


But its got your Secondary Air, since both our cars are California Emissions.


My cars calibration (as per the Rocker Cover) is IJ 204 AA, yours is xx 205 BA, so it might be a little different.




And the mid winter sun screws up a good picture...





Red goes to spark line on the carb.



AIR pump vac line has a VRESER on it



Front of the engine follows the VECI schematic, with "FRONT OF ENGINE" in DCK and 1-12B-R0 1981

Left most Blue VCV connected to VCKV and DV
Second Green VCV right most, and fed off ACV (out of view, its biege/brown/tan, and clips to the rocker cover).
Black VRESER hose off to far right, then


Colors are the key. These are the left to right colors, with the various valves and lines and links to match up.

This is the VOTM system (electric SOL V sits on rocker cover),



and the vac lines to the Evap canister

.

The air pump details depend on if your car has secondary AIR.







1. Ford never, ever did any favours with specific information on this carb. Its all nested among Fords generic year by year Vehicle Emissions Control Information

VECI, which governs

Vacum, Emissions, Carb, and Ignition line settings

The problem is Ford never had VECI diagrams for 1978 to 1980 1-bbl carbs, as there were

X shells with Carters,
Foxes with Holleys, and they made lots of 1946 model changes between CA and non CA spec with respect to the air pump, secondary AIR, and then the new B code 200 and C code 250 changes in 1980.

On my 1981, ignition to carb fitting has a priority delivery. It was a yellow line that was played off the ported vac against a dioded vac line on my VECI.

If you follow the VECI with all the letter codes broken out in active words, its easy to find, but it has just confused everyone else. ...so we used the pictures RED 78' supplied on his copywrited website to elaborate the diagrams. But be warned, his info is 1978 to 1980 specfic, and that doesn't help us 1981 guys who have the Secondary Air 3.3's



The reason why the 1946 is hard to tune is the missinformation and changes made to it from 1980 to 1981...they weren't ever feedback carbs, but they did have solenoids similar to the Feedback Carter YFA's used on Jeeps, F-trucks, E-vans and 2.3 Foxes and Rangers. It took me about four years to wade through the missinformation that happens because the carb looks like a feedback YFA, and requires a vaccum pump to set the pulldown choke, and has an A/C throttle kicker VOTM sesnor just like the Feeback Jeeps have.

Its just a 1-bbl Holley carb, but because its not a 1901, 1904, 1098, 1909, 1920, 1931, 1940 or 1945, the 1946 (and the similar 2.3 Tempo/Topaz 1949/6145/49/51/53) confuses the heck out of every Ford guy. even the smartest people.


2. Real quick, the choke is a pulldown choke unloader, and absolutely needs autocratic Czar set up as per the Ford manual set up requirement with a hand operted vac pump. As long as you've used the right process, it will work fine, and open all the way.The choke set up for 1-bbl carbs changed in the early late 70's, early 80's to the 25 psi of vac applied to the choke unloader.

you have to follow the time honoured apply vac procedure as per VECI , also common with the early 3.3 1-bbl






Expunge any thinking that the 3.3 carb is a feedback carb. A/C cars do have a control line to the throttle kicker, but its NOT a feedback carb. The "apply vac procedure" was also a primary way of triggering the code reader process in the 1980-1983 EECIII 5.0 CFI, but no 3.3 ever has been a feedback carb. Any references to Motorcraft 2150, VV 2700, VV 7200, Carter YFA, CFI, EEC II, III, IV, or MCU aren't relevent in any way to our 3.3's. These T, B and X code 3.3's never had a electronic feedback computer with the 5 or six wire computer reeder link.

Ford were just saving money in there Vehicle Emissions litrature, but for I6 3.3 guys, that just makes life to blqqdy dificult. Don't spend time looking in a black room for a black cat that isn't even there.


3. RED 78' is the best guy on the net for our I6 Fords, doanchaknow? But his info is 1978 to 1980 specfic.

See https://fordsix.com/viewtopic.php?f=...582790#p582790

I think RED 78' might have the two S and E ports around the wrong way in his picture, and Moostsie in his description too. S is certainly the down low port on the passenger side. Unlike the YFA, the Holley 1940/1945/1946 and 614x/615x family has the float bowel and choke at the back, and it has confused a lot of people. The fuel inlet isn't where the float bowl is, and some Autolites have the choke at the front instead, so its all a bit of a mish mash. Just as well you guys haven't got a RHD Fox 3.3, or the passenger side will be different depending on which country your in.

:bang:

Clockwise from front passenger side of carb is S, E, then V and then BV.





Items in the diagram in alphabtical order have numerical numbers from the 74 to sometimes 82 item list below. I'm gonna say it twice. Items from 75 to 82 are just numbers to put duplicate the VECI items in order, but you'll get the idea for oddball terms

The full list of items and codes on the VECI is
are

A Occurs Two times on the VECI, Item 82
A/CL BI MET, Item 3
A/CL CWM Occurs Two times on the VECI, Item 4
A/CL DV, Item 2
ACV, Item 5
AIR BPV, Item 7
CARB BV, Item 75
DIST, Item 11
E, Item 37
EGR, Item 12
FUEL T, Item 76
LCV, Item 60
MAN VAC, item 17
PCV, Item 81
PURGE CV, Item 30
S, Item, Item 35
SA-FV, Item 80
SLEEVE, Item 77
SOL V, Item 19
TO ATMOS, Item 78
TVV, Item 28
V, Item 21
VAC-SWITCH ASSY,Item 79
VCKV, Item 22
VCV 2X, Item 44
VDV, Item 63
VOTM, Item 53/73
VRDV, Item 26
VRESER, Item 23
VREST, Item 24

myle860, the VECI we both have and the Holley 1945 Mopar video info says the Spark valve is the one down low, the E is the one above it.

1981 VECI's were the first Ford cars with full VECI schemtics.

Again, working it out is 1980 to 1983 B and X code specific. It can put a fair old strain on the grey matter finding out where any of this stuff goes without an existing car to copy. The lines have color check valves/diodes to get priority flow that changes the vacuum source form Spark to Ported or Manifold via the later model vaccum and emission lines. This is very much like what the Mustang 4-bbl M codes from 1983 to 1985.

The Ford 1981 California emissions VECI list is for Fords trained service people, and not people like us,

I have had to use an 82 item name and claim it version of the list again and again; it has seven other visual VECI code items from 75 to 82, but its based on a hard return, digitized version of http://myzephyrs.com/vac_part_name.htm

Your important items are:

Item 8 BV: Bowl Vent (on top of the float tanks)
Item 17 MAN VAC: Indicating Manifold vacuum-Vacuum source for brake booster
Item 21 V VAC: short for Vacuum
Item 35 S Spark Port
Item 37 E EGR Port


Item on the VECI diagram are listed in red.

The full 74 item list excluding 75 to 82.:-

1 A/CL: according to Ford, that IS the air cleaner
2 A/CL DV: Air Cleaner Duct & Valve
3 A/CL BI MET: Air Cleaner Bi-Metallic Valve
4 A/CL CWM: Air Cleaner Cold Weather Modulator
5 ACV: Air Control Valve
6 AIR: This is a Secondary air injection Ford calls the Thermactor, short for Thermal Reactor. CA vehicles are installed with it as standard. Air Injection Reaction is what it stands for.
The thermactor system consists mainly of the air pump, the air pump diverter and bypass valves, TAB and TAD solenoids (if equipped) and the catalytic converter.
7 AIR BPV: Air Bypass Valve (aka Thermactor Air Bypass TAB)
8 BV: Bowl Vent (on top of the float tanks)
9 CARB: Carburetor
10 CPRV: Canister Purge Valve ( PURGE CV
11 DISTistributor of course.
12 EGR: Exhaust Gas Recirculator
13 EFCA: Electronic Fuel Control Assymbly
14 FLTR: Filter
15 FPR: Fuel Pressure Regulator
16 IVV: Thermactor Idle Vacuum Valve
17 MAN VAC: Indicating Manifold vacuum-Vacuum source
18 MAP: Manifold Absolute Pressure
19 SOL V: Solenoid Valve
20 SV-CBV: Carburetor Fuel Bowl Solenoid Vent Valve
21 VAC: short for Vacuum
22 VCKV: Vacuum Check Valve
23 VRESER: Vacuum Reservoir (Actually VRESER just stands for Vacuum Reservoir. It may or may not have a valve or Solenoid Valve inside it.
24 VREST is a vacuum restriction, usually at the thermally controlled valve on top of the thermostat housing.
*On 87 4V 460 F250 truck it is a simple blue plastic orifice inline with the vacuum line.
25 VRV: Vacuum Regulator Valve
26 VRDV: Vacuum Retard Delay Valve, as these can be used on more than just the distributor.
27 TVS: Thermal Vacuum Switch, and is different to a Dashpot. On Fords these are usualy located in the air cleaner.
28 TVV: Thermal Vent Valve. On fords they are mostly controlled by ambient air temps. Simular to a TVS. Located between the carb and the charcoal cannister.
29 PVS: Ported Vacuum Switch: Very simular to TVVs except on Fords they are used in the cooling system and are controlled by water temps.
30 PURGE CV: Vapor Canister Purge Valve
31 EVAP CANISTER ASY
32 Ford refers to theirs as an Idle Speed Control (ISC) solenoid
33 Idle Boost Solenoid (Orange Knob on 81, 82, 83 A/C Equiped 3.3's) or Throttle Kicker Control
34 Carburettor throttle Solenoid Positioner (Anti Dieseling Valve/Idle Stop Solenoid)
35 Spark Port
36 EGR Actuator
37 EGR Port
38 CAT is catalytic converter;
39 ENG is engine;
40 ACT - not sure, but on EFIs it means Air Charge Temperature sensor
41 Inlet Air Temperature Control
42 Green DVCV 2 port PVS vaccum switches
43 Blue TCVV 3 port vaccum switches
44 Dual Diaphram Distibutor
45 Black SDV Cold Start Spark Delay valve
46 Black SDV EGR Vaccuum delay valve
47 Deceleration Valve (PVS Cold Start lockout Dampened, Non Dashpot)
48 Non dampened or 2 port PVS (dampened) control EGR
49 Attitude and Position Fuel Trap
50 PVS Vacuum with Sintered Line Filters
51 Close Limit primary or Main Jets,
52 Lead plug sealed idle screws
53 Carburettor throttle Solenoid Positioner
54 Evaporative Emmission Control System
55 Anti Backfire Valve
56 EGR Valve Actuator
57 Vacuum Regulator/Solenoid
58 Solenoid Valve
59 Venturi Vacuum Amplifier
60 Load Control Valve
61 EGR B/P Transducer
62 Signal Conditioner
63 Ported Pressure Switch
64 Vent Valve Vacuum
65 Vacuum Controlled Switch
66 Vacuum Controlled Switch (Cold Temp)
67 Vacuum Controlled Switch (Decel Idle)
68 Vacuum Delay Valve
69 Vacuum Vent Valve
70 Delay Valve Two Way
71 Ignition Timing Vacuum Switch
72 Ignition Pressure Switch
73 TK (Throttle Kicker)
74 Mushroom caps for charcoal fuel vapor canister vents.


VOTM, Item 53/73
CARB BV, Item 75
FUEL T, Item 76
SLEEVE, Item 77
TO ATMOS, Item 78
VAC-SWITCH ASSY, Item 79
SA-FV, Item 80
PCV, Item 81
A Occurs Two times on the VECI, Item 82

For the later 1981 onwards 1946C carb, this is the full schemtic. You have to push the Magnifying glass icon to get it in full size.

http://i1215.photobucket.com/albums/...carburetor.jpg

[xctasy]

Green line to EGR

[xctasy]

Questions like "which of the many vacuum connections are you running distributor vaccum? Running PCV vacuum off the adapter, and I'm puzzled by the many options."

Its easy when you have vac line and emissions line pictures!

Then the red, yellow, green and blue color coded make simple sense

http://i1215.photobucket.com/albums/...e6/th_025r.jpg

The quick answer is the yellow line from the Duraspark goes to the double line to the base of the passenger side of the carb. See 6635, 6636, 6637 and 6741-1 below
http://i1215.photobucket.com/albums/...6/IMG_6635.jpg
http://i1215.photobucket.com/albums/...6/IMG_6636.jpg

http://i1215.photobucket.com/albums/...h_IMG_6637.jpg
http://i1215.photobucket.com/albums/...IMG_6741-1.jpg


Red Spark sustain port on pictures 8861

http://i1215.photobucket.com/albums/...6/IMG_8861.jpg,
8862 for the red coded stuff http://i1215.photobucket.com/albums/...6/IMG_8862.jpg.

Yellow is 8863 http://i1215.photobucket.com/albums/...6/IMG_8863.jpg
8864 is idle stop http://i1215.photobucket.com/albums/...6/IMG_8864.jpg
8865 is power supply wires http://i1215.photobucket.com/albums/...6/IMG_8865.jpg
8853 http://i1215.photobucket.com/albums/...MG_8853b-1.jpg (air cleaner detail),
8854 http://i1215.photobucket.com/albums/...6/IMG_8854.jpg,
8858 http://i1215.photobucket.com/albums/...6/IMG_8858.jpg,
8859 http://i1215.photobucket.com/albums/...6/IMG_8859.jpg,

For 8860 and 8868 general info, just ammend the file extension to 8868.jpg


I have about 130 pictures and videos itemised in this list. One of them will be just the info you need, so hange in there.

1 3416
2 3417
3 3418
4 3419
5 3420
6 3421
7 3422
8 3423
9 3424;
10 3425
11 3426
12 3427
13 3428
14 3429
15 3430
16 3431
17 3432
18 3433
19 3434
20 3435
21 3436
22 3437;
23 3438
24 3439
25 3440
26 3441
27 3442
28 3443
29 3444
30 3445
31 3446
32 3447
33 3448
34 3449
35 3450;
36 6376
37 6377
38 6378
39 6379
40 6380
41 6381
42 6382
43 6383
44 6384;
45 6385
46 6423
47 6424
48 6425
49 6426
50 6437
51 6444
52 6445
53 6446
54 6447
55 6448
56 6449
57 6450
58 6451
59 6452
60 6453
61 6454
62 6455
63 6456
64 6470
65 6477
66 6483
67 6488
68 6560
69 6570
70 6511
71 6541
72 6542
73 6543
74 6567
75 6594
76 6572
77 6573
78 6574
79 6575
80 6576
81 6577
82 6578
83 6579
84 6580
85 6581
86 6582
87 6585
88 6584
89 6585
90 6586
91 6587
92 6588
93 6589
94 6594
95 6590
96 6591
97 6592
98 6593
99 6594
100 6595
101 6596
102 6597
103 6598
104 6599
105 6600
106 6601
107 6602
108 6603
109 6607
110 6608
111 6610
112 6611
113 6612
114 6615
115 6616
116 6613
117 6614
118 6374
119 6375
120 6741-1
121 8860
122 8861
123 8862
124 8863 is Yellow line
125 8864 is idle stop
126 8865 is power supply wires
127 8853 (air cleaner detail),
128 8854
129 8858
130 8859

[myle860]

I think what is happening is the egr valve is open too early and its advancing the timing at the same time. When I disconnect and plug those 2 lines the car runs fine. Also had to rebuild the carburetor seems there was a extra screw in the accelerator pump binding that up

[xctasy]

See below

[xctasy]

Four questions.
1. What VECI sticker numbers. Could you post it cleaned up a little with a rag, and post the E1 XX XXXX XX DXX num?

Mine is E1 BE 9C485 CA, DCK


It has LHS and RHS info.


Here's my RHS info broken down. Yours is different. I need to see both sides if you could manage it, cuase I reckon the EGR line routing is different on non A/C cars.



2. Whats you full engine calibration sticker code?

Mine is IJ 204, with 1-12B -RO on the rhs.

Yours is differnt, and the RHS no is the calibration VECI on RED'78's website



IJ 204 AA, but 1-12 RO is the clibration VECI you check those lines agianst, which you'll find on RED'78's web site.

My cars calibration (as per the Rocker Cover) is IJ 204 AA, yours is xx 205 BA, so it will be DIFFERENT.

Already, without all the VECI visible, your Point "A" is a checking point in the instructions on the LHS of the VECI sticker lookes different.

So there is a difference between yours and mine,

Because you don't have A/C, your set up is missing an extra vac check point "A" on the EGR circuit. And you don't have the idle control SOL that A/C cars do, so Ford will have a slightly different vac arrangement for secondary AIR.

I'm pretty sure the problem is simple, and a variance on the set up I had on my 81 A/C auto.


If you post your VECI diagram in full like mine, we can see where the EGR line goes EXACTLY.

Ford are pretty smart, there will be a difference if there is only one Hand Pump vacuum check point.

I note that BTD has a CA emissions 81, but its 4-speed T4 manual but has no A/C either, so no idle kicker, or what is called variously the VOTM system (electric SOL V that sits on rocker cover of A/C cars)


3. Note BTD's AIR pump is long since gone, but is Is there a diffrence in the line arrangement?

Here is it here.

Engine 3.3 200


I'll ask for VECI's from each of you because its likely to be something really simple like that.


4. As for the carb, what part do you think has the extra screw that's binding it up?

For the later 1981 onwards 1946C carb, this is the full schemtic. You have to push the Magnifying glass icon to get it in full size.

http://s1215.photobucket.com/user/xe...retor.jpg.html
Everything has a number if your eyes are good enough.

Kits are generic, and Mikes cars and others haven't yet done a rebuild video on the 1981 to 1983 1946C Holleys, there are a few bowle vent and other differences.

Another one is the check weights. Its easy to sub in the wrong part, and sometimes, they may have been wrong from previous service.

[myle860]

The sticker is just one I found at a junk yard to try figure out what im dealing with. My original hood is long gone. The car was half capri we I got it. The valve cover is one from a junk yard so I dont think its the correct sticker anyways. For the carb I broke down and bought a NOS one and bolted it on. The screw was stuck in the accelerator pump spring when I found it.

[xctasy]

Cool. Thats normal :-)

Nothing stays original normally. I was just lucky with my 81 3.3, and nothing was changed.


You'll get this beat. NAVYCAT whent through the same head bending sh!+ for his CA emissions 81 White Magic Capri...a long process of repeatedly trying components to find that all the while, the stock parts were okay. The car is now in Australia with the smog gear off,and there are photos of it below.

Afew notes

Line Color codes are:-

They often correspond to a stripe color or hose color, but not always.

Typical Color Codes - Vacuum Diagram
Red = Main vacuum
Green = EGR function
Orange = Heat control Valve (exhaust & intake) (AKA heat riser but more complex)
Yellow = Distributor advance / from the TAD Solenoid (driver's side Forward Solenoid) to the TAD (Diverter) Valve located at the rear of the Intake Manifold (nb//On V8's, I6's, its normaaly drivers side - xctasy)
White = EGR vacuum (source)
Black = Mainly used for the Evaporative emissions control
Black = Thermactor ACV or Diverter valve
Blue = Throttle Kicker control
Pink = Thermactor Air Bypass Valve (BPV) (from the TAB Solenoid (driver's side rear solenoid) to the bottom of the Thermactor Air Bypass Valve)

......

Can someone tell me what the difference is between a Vacuum Check Valve (VCV) and a Vacuum Delay Valve (VDV)?

Just to make your statement on the VCV a little clearer for the asker, a vacuum check valve will hold against vacuum indefinitely in one direction- meaning vacuum can travel through the valve unrestricted in one direction but it can never travel through the valve the opposite way. It's just like a standard electrical diode, if that helps at all.

Could you confirm that you have item 19/53/73 hooked up via the dashed line in this revised VECI?



If so, Tthen you have one minor matter...

Your VRDV to the air cleaner is Bluee Black White, not Red Black White like mine.


Everything lookes right, BUT there's a major issue for you....

1. My EGR valve was a 135. A replacement might not be the right one for what is an A/C equiped VECI in your case.

2. Yep, that's right, its all that A/C stuff the might be messing things up.



3. The Ford Service Manual VECI 1-12-RO has been amended to include:-


Sol V, Item 19, an idle Vac solenoid.

SOL V is only when A/C equiped, and controls the VOTM. Its those dotted lines, and its a lot of extra stuff that has a tuning specfic that you'll have to follow from post #3 above, LHS of the E1 BE 9C485 CA, DCK VECI.

All of it.

Differences are:

1. Item 73 is actually the VOTM (Vac Operated Throttle Motor), not an electric motor, but operated by item 53/73, the Carburettor throttle Solenoid Positioner or TK (Throttle Kicker) in other FoMoCo speak. It was put into place elseware to fix idle problems with A/C, but also in Aussie 1976 to 1982 Falcon sixes.Without it, idle is not well modulated.

2. You don't have A/C, yet have all the A/C VECI gear. That means you have to treat it as non running A/.C.


I.e. you have the A/C throttle kicker, so you need to assume A/C off and tune as per the LHS of the VECI.

Similarly Your Green Purge CV will have to use the full A/C circuitry , and your carb will have to use the VOTM and all the dotted lines.

It'll be venting if the dotted line A/C VECI stuff isn't hooked up. . The wire hookups from the non existant A/C unit will have to be switched like they are on A/C cars. Or it'll e open looping to wrong feedback data. Its not a feedback carb, but if the A/C models VOTM is on the carb, it'll need to work if its looking for a pulse Width Modulation value or analogue signal. Mis tracking idle was a typical early 80's issue.

If I were smart enough, we'd figure what was different between the A/C and non A/C carbs and Purge CV and all the dooted line crud, and set it back to non A/C simplicty, but I've never seen a non A/C 1-bbl Holley 1946C, and mine worked perfct even with broken A/C, so i'd advise you just continue.

If you can a find a White black and red VRDV to Item 4, the A/CL CWM, it might help if you still have matters after tuning the A/C as per the VECI.

They have diiferent specs, and although these are not up to date, you can see how much the spacs vary for 71-78 Mavericks and Cometes.

I realize this is an old thread but it keeps coming up in my searches to make heads or tails of the vacuum system.

I found this list of FORD vacuum delay valves which may be more relevant to our cars than the list previously linked to.

Spark Delay Valve

		Time in Seconds
Color Code	I.D. Number	Minimum	Maximum
White/Brown	2	2	5
White/Green	20	9	20
Black/Grey	1	1	4
Black/Brown	2	2	5
Black/White	5	4	12
Black/Yellow	10	5.8	14
Black/Blue	15	7	16
Black/Green	20	9	20
Black/Orange	30	13	24
Black/Red	40	15	28

The list was found here, http://www.1bad6t.com/Maverick/repai...ntrols_02.html

In one post, our 2.3 Turbo carb Ford guy gr79 helped another member pacecartodd get three new diodes from the NPD catalog (pages 105 to 145 2015 ). #37 on Page 2.

http://vb.foureyedpride.com/showthre...8carb%29/page2

So there is all the support in the world for you.

I think you'll find that Ford were pretty strict getting those emissions down, and that is all you need to do is follow the stock, original VECI lines for an A/C Capri.like NAVYCAT / FoxyCapri's.


Oh, and here is what it all lookes like unhooked...

G'day Dean, you'll have to excuse my ignorance, but I have no bloody idea what all that emissions stuff is or what it does. I'm an old school mechanic, plugs, points and an oil change, that's for me!

Anyway, attached are 2 pics of a lot of the rejected stuff off my I6 200, along with a close up of the item I thought that you were talking about. Hope all this helps, and I definitely don't have the EXH light. Cheers, Terry
Attachment 81049 Attachment 81050

If not in service, the idle tacking falls out due to component aging or sometimes just the akwardness of finding info form Ford, like this part below. Its in perfect shape, but everything is cutom to application, and it has a resister in line for some applications. So just a contiuity and restance test can rsult in the wrong thinking. If one piece of info is missing, you start to think its a component fault, but that is seldom the case....

Thanks. Although my components are operating in reverse to achieve the same operation.
My '83 is an early build (Oct. '82). (if that might explain the differences ?)

Anyway, my vacuum switch is definitely closed (13.2 ohms) at atmosphere (from 0 to 8 inches)
and the goes to open circuit with 8 inches or more.

Attachment 108554

Also, my TAB and TAD solenoids "pass through" vacuum when they are not energized.
When energized the solenoids block the source vacuum and vent the "device" to atmosphere.

The end result is operation just as you described.

What is the reason to send thermactor air upstream during heavy load ?

Thanks
Todd H.

Anyway, my vacuum switch is definitely closed (13.2 ohms) at atmosphere (from 0 to 8 inches)
and the goes to open circuit with 8 inches or more.

Your switch is bad. You should have 0.0 to 0.2 ohms across closed contacts. 13.2 ohms is indicating that the contacts are ether dirty or pitted and are not making good contact which will cause a voltage drop through the switch.