TVSV and drivability

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sdoan
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TVSV and drivability

Post by sdoan »

I discovered a fixable failure in a TVSV yesterday! They leak between the brass base and the plastic tower. If you put them in water and blow through the "N" pipe (lowest) you will see bubbles come from between the base and the plastic. It will also not hold vacuum if you plug the other ports and apply a vacuum. I had 4 to check and they ALL leaked.

My fix was to use some medium viscosity super-glue to build a fillet at the joint between the plastic and brass. The super glue appeared to creep down into the joint and seal it. After sealing in this way the TVSV would hold a vacuum on the lowest port.

Drivability: The TVSV in the car was removed and testing found it to be OK at low (<45 F) and medium (65-122 F) temps, but not at the high temp. Apparently the internal shuttle was not moving far enough (see picture). I had another TVSV that was cracked so I pulled it apart to see what it looks like.

Image

The pin in the base apparently pushes out more at higher temperatures pushing the spool-shaped shuttle further up in the plastic cylinder. The shuttle is rubber and seals against the inside of the plastic cylinder. As the shuttle moves it opens or closes ports on the cylinder.

I found that the defective TVSV would work correctly if I heated the base in the flame on the stove. I gave it several cycles of heating an cooling to see if the shuttle could be induced to move further so it would work correctly at lower temperatures but it never did work at the correct temperature.

When I replaced the TVSV with one that worked correctly I found that the car had a much smoother off-throttle to on-throttle transition at small throttle openings. Prior to replacement the car would tend to violently buck or surge during low speed, low rpm throttle transitions. This occurs when almost coasting at 25-30mph in 3rd or 4th gear and low rpm. This has happened in other T4wds I've driven so it seems pretty common.
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Re: TVSV and drivability

Post by xirdneh »

I did a thing on the TVSV a while back.
I found the same problem with the pin travel being short
i reassembled with a short piece of a nail about 1/8" long and the approx diameter of the pin added to increase length of travel
i have been happy with the results
Love those Tercell 4x4 wagons but they sure suffer from road noise.
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Re: TVSV and drivability

Post by stanrob »

I realize it's been 6+ years since the last post on this subject. Did it get moved over to another subject? I'm thinking there must be an epidemic of leaky and/or improperly functioning TVSVs. I know that the following message is too long, but in this case there's a lot to think about.

I recently discovered that BOTH of my most recent T4Ds have TVSVs that won't hold any vacuum at 70 degrees F. Using a gauged vacuum pump, I drew air from one port while blocking the other four. No vacuum! I repeated that test for each port. From sdoan's report, he actually found an air leak at the base of his TVSV, which he was evidently able to patch. Meanwhile, xirdneh discovered internal pin travel problems with his TVSV, which he was evidently able to patch.

Among the implications of no vacuum at 70 degrees F: no choke breaker 2 or choke opener. Meanwhile, choke breaker 1's vacuum hose was simply capped off by Petros (who brought me that latest T4D). So choke opening is done ONLY by the electric heater mechanism - later than needed.

I believe the CB1 cap-off explains much, if not all, of this car's cold-engine drivability problem. The first phase of choke breaking is simply not happening. CB1's diaphragm is supposed to open it to 39 degrees from horizontal within a few seconds of startup (FSM at page FU-23). (I gave CB1's diaphragm some bona fide vacuum and it worked.) I started the engine and watched. Airflow opened it a little bit, fluttering away at 20-25 degrees, and that was all, even after a full minute.

Of course the CB2 and CO diaphragms should get vacuum in their turn, and that's not happening either. Meanwhile, from my examination, we need a jet (currently missing) and an engine vacuum source for CB1 (not evident on this carburetor, unlike what's suggested in the upper left drawing on FSM page EC-49).

As regards fixing this nightmare:
(1) Is it possible to get a non-defective TVSV to replace my defective one?
(2) How does one uninstall the defective one? Is there a special tool?
(3) Where can I get a jet (currently missing) for CB1?
(4) Where can I hook that jet up to engine vacuum? With an airtight TVSV, perhaps tee into the tube feeding port K?
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Petros
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Re: TVSV and drivability

Post by Petros »

occasionally new ones show up on Amazon or ebay, but I can not find any now.

This newer type with only two ports is available, perhaps it could be adapted by doubling up, by passing or disabling some of the ports on the Tercel.

https://www.partsgeek.com/7j8llgy-toyot ... uum+Switch
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The Professor
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Re: TVSV and drivability

Post by The Professor »

Petros, what are the search terms you've used to find them in the past? Part numbers, key words?
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Petros
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Re: TVSV and drivability

Post by Petros »

The Professor wrote: Tue Oct 31, 2017 9:28 am Petros, what are the search terms you've used to find them in the past? Part numbers, key words?

yes, both. Toyota TVSV turns up a lot of the newer types, both the two port type (like above) and the newer ones with an eletrical connectors. I also searched the part number I got from a web site with pics of the emissions/fuel system with part numbers called out.

there is also a way to do a google image search, but I have not tried that one.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
The Professor
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Re: TVSV and drivability

Post by The Professor »

Petros wrote: Tue Oct 31, 2017 9:47 pm
The Professor wrote: Tue Oct 31, 2017 9:28 am Petros, what are the search terms you've used to find them in the past? Part numbers, key words?

yes, both. Toyota TVSV turns up a lot of the newer types, both the two port type (like above) and the newer ones with an eletrical connectors. I also searched the part number I got from a web site with pics of the emissions/fuel system with part numbers called out.

there is also a way to do a google image search, but I have not tried that one.
You wouldn't happen to have that part number handy, would you?
1975 Subaru SuperStar wagon
1984 Subaru Turbo-Traction wagon & hardtop
1987 Subaru RX 3-door
1987 Subaru RX Type-RA 3-door
1987 Toyota Tercel SR5 wagon
1999 Subaru Forester S
2002 Subaru WRX sedan
2019 Subaru Outback 2.5i Limited
stanrob
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Location: Wayland, MA, USA

Re: TVSV and drivability

Post by stanrob »

I'm getting nowhere with the first-five-minute undrivability of 85TTW#3 (which Petros sold me and delivered here). With all of its other problems, and my gross inefficiency in solving them, I'm thinking that I'd better find another car and let this one go. Is there anybody nearby who loves T4Ds, wants a rust-free body, is up for the challenge, and willing to bail me out?

Meanwhile I'll continue to piddle around with it. Perhaps the next baby-step is to get CB1 working. (For reasons not yet known to me, Petros delivered 85TTW#3 with CB1 completely disabled.) That doesn't depend on having a good TVSV. I just have to find a jet and a way to tap into plain old engine vacuum.

As regards the TVSV: I wish I could be confident that a good TVSV would provide drivability. In fact, 85TTW#2 (my daily driver 2005-2016) was relatively drivable DESPITE its defective TVSV. Perhaps that's due to CB1 kicking in.

Meanwhile, I did a cold phase test of the TVSV in my long-dead 83 Hatchback. It passed! In order to do the medium phase and hot phase, I'll have to remove it. There's not much elbow room in there! What tool(s) enable you guys to loosen and remove a TVSV?
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Petros
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Re: TVSV and drivability

Post by Petros »

I use a quality open end 19 mm wrench. might help to heat the casting it screws into if it is really stuck, Usually it comes out okay.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
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Petros
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Re: TVSV and drivability

Post by Petros »

are you talking about the choke breaker? If yours is no good I may have one I can send you to try out. I may also have some TVSVs also, but they are old and I do not know of their condition.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
stanrob
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My tercel:: Two 1985 Tercel SR5 4WD, Cal. emission controls, one now a parts car (good engine & transmission, still had full power at 310K), another, a low-rust project car, with 307k miles, from Petros
Location: Wayland, MA, USA

Re: TVSV and drivability

Post by stanrob »

Quoting:
are you talking about the choke breaker? If yours is no good I may have one I can send you to try out. I may also have some TVSVs also, but they are old and I do not know of their condition.
Answer:
Regarding "the choke breaker": No. Just to cover the subject, I applied vacuum to each of the three choke-related diaphragms (CB1, CB2, and CO) and they all pulled by roughly the amount they should. The problem is they're getting no vacuum, CB1 because it's capped off, and CB2 and CO because of the nonworking TVSV, if not more.
Regarding your possible store of TVSVs: It's good to know of the possibility, but please hold off. On a nicer day, I'll try to remove the 83 Hatchback's TVSV and test it more thoroughly. Do you have any advice on what sealer to use for reinstallation?
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Petros
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Re: TVSV and drivability

Post by Petros »

I use RTV as my preference because it seals against coolant. But Permatex Form-a-gasket (non-hardening black paste) also works.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
stanrob
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Joined: Thu Aug 30, 2012 3:03 pm
My tercel:: Two 1985 Tercel SR5 4WD, Cal. emission controls, one now a parts car (good engine & transmission, still had full power at 310K), another, a low-rust project car, with 307k miles, from Petros
Location: Wayland, MA, USA

Re: TVSV and drivability

Post by stanrob »

I finally achieved removal of the 83 Hatchback's airtight TVSV, but the story goes on. Got sufficient access by removing the temperature sender. Used 19mm open end wrench as Petros suggested. However, in the course of removal I accidentally fractured the bottom port "N". Now it leaks unless I hold it in position. What a drag! I'll try to patch w/superglue unless I hear contrary advice.

According to ToyoDIY.com, the part number is 90925-02076. Price quoted is (factory?) $146.64.
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Petros
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Re: TVSV and drivability

Post by Petros »

plastic parts this old can be brittle and fragile, super glue is a good fix. You can also double coat over the crack with a bead of polyurethane adhesive, adding some thickness to it, to give it more strength.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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irowiki
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Re: TVSV and drivability

Post by irowiki »

I still have a brand new one kicking around, I paid $100 for it.

It could be yours for 100 + shipping.

Otherwise I might make a display case for it :lol:
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