Are these symbols for a Check Valve?

[Slow Left]

Does anyone know if these pairs of arrows (see red arrows pointing to 2 sets of them in the first image below) indicate that there is supposed to be a Check Valve in line with that particular vac route?
If so, what does it look like and does someone have a part number?

If you notice in the second image below, there appears to be some sort of check valve in the hose that connects to the Air Filter.
This hose is part of the Choke Opener vac circuit.
Currently, I have no check valve installed there, which means that when BVSV 2 opens up, the Gas Filter could be pulling air from the Air Filter, causing a vac leak and not allowing enough vac to be generated at the Choke Opener diaphragm?

And if that is a symbol indicating some sort of check valve, then there should also be a check valve in line with the hose attached to the HAC Slow Port at the base of the carb, right?

Thx.

 

[LAMBCRUSHER]

orifice restricter. all I know...

 

[Slow Left]

Another image of the Choke Opener circuit from page 3-42 in the 1981 2F Emission Control FSM.

The right side of the image shows that when the BVSV opens at operating temp, that the route to the Air Cleaner seems to be blocked so that vac can build up enough to operate the Choke Opener Diaphragm...those curious pairs of arrows are there in the drawing...magical arrows!?!

 

[Slow Left]

orifice restricter. all I know...

Is that the 'technical' name for them? Really?

EDIT:

I found another link addressing these 'orifice restrictors' (it doesn't get any easier typing it again):
https://forum.ih8mud.com/threads/dizzy-venting-need-some-insight.290646/

Unfortunately there was a link to part numbers in that thread, but the link is dead...

 

[Output Shaft]

Well.....
Since Toyota specifically called out check valves for AI and HAC, and an actual component is drawn, my take on it is that the >< arrows do not specify an actual component (check valve).

It is easy enough to check:
See the EGR vacuum modulator for example. It shows the mysterious >< hieroglyph as well, but sure as the 2F is the slowest engine on the fwy, there is no check valve attached to the modulator. You could blow/suck through that port if you dare. You will find out soon enough.

My conclusion: I don't know what it means. But I don't think it is a check valve that you could purchase or install.. if it is one at all.

 

[LAMBCRUSHER]

if you look very closely at the tee that is in you vacuum loom, it may have some indicator as to whether or not is has a restriction in one leg- I believe these were built into the fittings and indicated as such on the fittings themselves. A good napa parts guy should also have some generic valued restrictors in a box on a shelf...are they very important? IDK...

 

[Slow Left]

Well.....
Since Toyota specifically called out check valves for AI and HAC, and an actual component is drawn, my take on it is that the >< arrows do not specify an actual component (check valve).

It is easy enough to check:
See the EGR vacuum modulator for example. It shows the mysterious >< hieroglyph as well, but sure as the 2F is the slowest engine on the fwy, there is no check valve attached to the modulator. You could blow/suck through that port if you dare. You will find out soon enough.

View attachment 1007981

My conclusion: I don't know what it means. But I don't think it is a check valve that you could purchase or install.. if it is one at all.

Yeah, I think LAMBCRUSHER is right...they're called restrictors...similar but different than check valves...
I'm gonna add them in and see if the Choke Opener starts working better...if I can find them cheap at NAPA...

 

[Slow Left]

if you look very closely at the tee that is in you vacuum loom, it may have some indicator as to whether or not is has a restriction in one leg- I believe these were built into the fittings and indicated as such on the fittings themselves. A good napa parts guy should also have some generic valued restrictors in a box on a shelf...are they very important? IDK...

Problem is I went through and replaced all those OEM 3mm hoses with new ones...

I'll try and hunt down some restrictors that will fit the 3mm line and see if the operation of the Choke Opener improves.

Thx.

 

[LAMBCRUSHER]

think of them as vacuum jets...drill a small hole thru a .177 caliber pellet and jam it into the hose at the tee...

 

[Output Shaft]

It seems to me that the choke opener is either open or closed depending on temperature. It doesn't seem like it would matter if there is a restrictor or not. Pg 3-42

The CHOKE BREAKER actuation on the other hand is delayed by it's VTV and start-up stumbling (if that is the issue) could be related to that VTV.

 

[Slow Left]

It seems to me that the choke opener is either open or closed depending on temperature. It doesn't seem like it would matter if there is a restrictor or not. Pg 3-42

The CHOKE BREAKER actuation on the other hand is delayed by it's VTV and start-up stumbling (if that is the issue) could be related to that VTV.

Agreed about the CB, but if you look up in post #3, you'll notice that when the BVSV 2 opens, then the vac line on that far side splits...one path leading to the CO and the other to the Air Filter...the restrictor is on the Air Filter side...presumably to prevent an excessive air vac leak.

 

[Output Shaft]

Yes, u r right.
The vac will pull more strongly on the CO with the restrictor. Without a restrictor, it doesn't seem like the CO would work and provide a vac leak.

You could test your theory (vac leak) by just plugging the CO vac hose going to the air cleaner to get rid of that little vac leak & seeing if anything changes.

& if you wanted that little restrictor, I am sure the used Land Cruiser parts guys will have one.

[Edit: replaced CB with CO in text above]

 

[Slow Left]

Yes, u r right.
The vac will pull more strongly on the CB with the restrictor. Without a restrictor, it doesn't seem like the CB would work and provide a vac leak.

You could test your theory (vac leak) by just plugging the CB vac hose going to the air cleaner to get rid of that little vac leak & seeing if anything changes.

& if you wanted that little restrictor, I am sure the used Land Cruiser parts guys will have one.

Just a quick clarification, the vac circuit with the restrictor is the Choke Opener (CO) circuit. The Choke Breaker (CB) has a VTV valve in line between it's vac source and the diaphragm.

But yes, that is a good test. When I reinstall the carb I'll give it a try.

 

[Slow Left]

I think I have found 3 circuits that use this restrictor:
Choke Opener (between Air Filter and Gas Filter)
HAC Slow Port (right off the Slow Port at the base of the carb)
Port P on the EGR Modulator

I'm wondering if not having the restrictor before the Port P on the EGR Modulator is causing the EGR Valve to open too early...this might explain that flat spot ~1,800 rpm (ie mid-RPM stutter).

 

[Output Shaft]

There is no restrictor externally of port P.

What some guys have done is install a passive VTV on port Q vac hose leading to the EGR valve to slow the activation of the EGR valve (like the one going to the diaphragm for vac advance). It does help delay the opening of the EGR, but can cause it to sometimes not shut as quickly compared to without... An easy thing to try.

When it comes to engine hesitation above 1500 RPM, the EGR is ALWAYS suspect.
Easy enough to rule that out too.

 

[Slow Left]

There is no restrictor externally of port P.

What some guys have done is install a passive VTV on port Q vac hose leading to the EGR valve to slow the activation of the EGR valve (like the one going to the diaphragm for vac advance). It does help delay the opening of the EGR, but can cause it to sometimes not shut as quickly compared to without... An easy thing to try.

When it comes to engine hesitation above 1500 RPM, the EGR is ALWAYS suspect.
Easy enough to rule that out too.

So is there a restrictor internal to port P of the EGR Modulator?

I'll go back and recheck the EGR system and even go around it to see if the symptom goes away, but both that EGR Valve and Modulator were brand new and the system test OK back before I dove down the rabbit hole...

 

[LAMBCRUSHER]

all the other restrictors I have seen have been in the tees...are you guys certain that the tee leading to the egr modulator doesn't have one? I see the diagrahm shows the restriction being at the modulator, but it may also be located in the nearest tee upstream; just drawn funny on the m,ap.( but toyota has never done that before...)

 

[LAMBCRUSHER]

There is no restrictor externally of port P.



When it comes to engine hesitation above 1500 RPM, the EGR is ALWAYS suspect.
Easy enough to rule that out too.

this is what I have been wanting to say...do the VSVs test as good? could the egr vsv be opening inappropriately?/ stuck open; not closing all the way??? I ask cause you have replaced the other major components there...

 

[Slow Left]

all the other restrictors I have seen have been in the tees...are you guys certain that the tee leading to the egr modulator doesn't have one? I see the diagrahm shows the restriction being at the modulator, but it may also be located in the nearest tee upstream; just drawn funny on the m,ap.( but toyota has never done that before...)

When I get hold of some restrictors I'll install on at EGR port P...it makes sense to me that there would be one there...and then see how it works...

this is what I have been wanting to say...do the VSVs test as good? could the egr vsv be opening inappropriately?/ stuck open; not closing all the way??? I ask cause you have replaced the other major components there...

VSVs tested good last time around, but I'll go back and recheck...I'll also bypass the EGR altogther and see where that get me.

Thx.

 

[Output Shaft]

I'll also bypass the EGR altogther and see where that get me.

So far down the rabbit hole you will never want to see god's green earth again.