Emissions system questions (VTV, vac advance) (1 Viewer)

[Carpe Discus]

I'm going through my emissions equipment (on my '83 fj60), and I had a couple questions. For the record, I had slightly high CO, then pretty high NOX, when I replaced the EGR modulator and EGR VSV. A bonus, it seems to clear up that "it sometimes runs horribly at stoplights when it's hot" thing I sometimes have.

[STRIKE]1. The VTV on the left side of the engine that's before the distributor diaphragm--is there a problem if that is the blue VTV instead of the brown VTV? Because that's what I have (blue one side, black the other). What's the difference between the colors, anyway?[/STRIKE]

Bah! Missed the thread with the answer.​

[STRIKE]2. If the blue one is OK on the left, is the blue side supposed to replace the brown side as far as its orientation? The picture shows the brown side facing the diaphragm[/STRIKE].

Also answered in the linked thread.​

3. The emissions FSM says that the VTVs should have a "restricted" flow in one direction. I have no flow in that direction; is that acceptable?

4. The lines to the distributor main diaphragm and sub-diaphragm are switched. Is that a problem, and what would be the effect of this?

 

[1911]

3. The emissions FSM says that the VTVs should have a "restricted" flow in one direction. I have no flow in that direction; is that acceptable?

Yes, that is the way they are supposed to be; "restricted" is Engrish for "one-way".

 

[hank14]

Blow in one side of the VTV and put some extra vacuum tubing connected to the other side. Put the free end in some water and watch for bubbles to see if it is functional one way and restricted the other way.

Having the vacuum hoses switched on the distributor vacuum advance can cause pinging if you're at sea level or your HAC valve is not working.

I like how you updated you first thread with the links- makes it much easier to read through it and address your current problems!

 

[2mbb]

Yes, that is the way they are supposed to be; "restricted" is Engrish for "one-way".

a VTV is NOT a one way or "check" valve. With a VTV air flows unrestricted in one direction, and restricted, meaning at a controlled rate, in the other direction.

If the VTV does not allow flow in one or both directions it is not working properly.

 

[Spike Strip]

FWIW - I had a couple of the VTV s that would only work one way. I sprayed some plastic-safe cleaner/lube in both sides, GENTLY blew out the residual lube, and then they worked. Use a hand-vacuum pump to test, if you have one.

 

[Carpe Discus]

FWIW - I had a couple of the VTV s that would only work one way. I sprayed some plastic-safe cleaner/lube in both sides, GENTLY blew out the residual lube, and then they worked. Use a hand-vacuum pump to test, if you have one.

What's a good plastic safe cleaner, anyway? I see people recommending carb cleaner for this but I would think it would not be kind to the plastic.

 

[Spike Strip]

CRC Industries Product Detail

Or an MAF sensor cleaner, or similar.

I suppose you could also use some electrical switch cleaner. If carb cleaner works, too, that's good...

 

[1911]

a VTV is NOT a one way or "check" valve. With a VTV air flows unrestricted in one direction, and restricted, meaning at a controlled rate, in the other direction.

If the VTV does not allow flow in one or both directions it is not working properly.

Well, you learn something every day! Mine were obviously not working properly; I guess that's why my truck ran so much better after I de-smogged it.

 

[Brice]

Which way is the black part supposed to face?

 

[CaptClose]

Which way is the black part supposed to face?

 

[Brice]

thanks Cap. Terrific pic. Just so I am clear, though, since mine looks slightly different: the black end faces TOWARD the vacuum source, is that a fair statement?

 

[CaptClose]

Yes... black side faces the grill, blue faces the firewall.

Note: mine has a black and a blue side. These plastic bits have been known to morph colors over the course of three decades. Black tends to stay black though... once you wipe all the grime away anyway.

 

[Brice]

thanks again, Cap.
The orientation of this part on my engine is more sideways rather than front/back.
For clarification purposes, does the black end face TOWARD the vacuum source?
Sorry to sound annoying; don't mean to be at all. Just need to know an installation "rule" for this part.

 

[CaptClose]

Yes, for those playing at home...

The primary advance connects to the carburetor "Advancer Port". This is the port on the back of the carb (facing the valve cover) at the 9 O'clock position. It can be identified in the illustration and photo below:

The black side of the VTV would face toward the vacuum source on the carb.

 

[Brice]

Outstanding, thank you sir!

 

[CaptClose]

Glad to help brice.