Vacuum Check Valve

[smokerx]

My 83 or 86 3 AC engine was only cranking with gas poured into the carb. throat. I pulled the hollow bolt that runs from the fuel line into the carb and cranked it and caught some gas. Did a burn test and it lit on fire. Pulled the carb to clean it and caught the gas from the bowl. did a burn test and it burnt like water. Cleaned the carb and pulled alot of green gunk out of the bowl.

While pulling the vac. lines to remove the carb I blew on the line that runs to the orange vacuum check valve that sits on the valve cover (normally hidden from view by air filter housing) then runs to the distributor vacuum advance. No air passed through and the plastic was rotten from heat. I thought it was this check valve

http://www.ebay.com/itm/86-88-Toyota-Su ... bb&vxp=mtr

and saw it running $30-$50 new. That check valve is in the front vac. lines tho. So after thinking about using an aquarium check valve I searched for a universal vacuum check valve

http://www.ebay.com/itm/Help-Dorman-471 ... 6d&vxp=mtr

and figured out I can pick one up from the local auto parts store for a couple of bucks.

[xirdneh]

i have checked that particular one way check valve on lots of tercels
never found one that i could detect any air passing through

[irowiki]

That ebay link is actually a vacuum transmitting valve! They seem just like a check valve in most cases, I wondered what the difference was. A quick google found the patent by toyota:

Disclosed is an improvement in a vacuum transmitting valve for an exhaust gas purifying system on an automobile engine, of the type which has an inlet chamber and an outlet chamber divided by a partition which is provided with a vacuum transmitting orifice. The inlet chamber has at least one opening for bleeding purging air into the inlet chamber to expel therefrom any gasoline vapor that might otherwise reach and clog the orifice.

I guess it's to keep the vapors out?

[smokerx]

http://www.nonags.org/members/nijqk/83FedVacR.jpg

I smashed the old piece to see what was inside and it's a filter disk then a small metal partition in the center with a pin hole.
Obviously not a check valve. Finally found the above diagram on page 94 and it's #23 (restrictor orifice). Seems to run with the check valve installed there with direction of flow going toward the distributor tho.

Was getting confused from too much carb cleaner on the brain.

[smokerx]

Update:
Finally got it running again. After rebuilding and dipping the carb and replacing the fuel pump it still had the same issue of not running unless I poured gas or carb spray down the carb throat. Last time it ran I had done a valve tune with the engine warm. This either changed something to make it to where I have to plug the hose connecting to the air filter (with the filter off)to get it to run; or the hollow bolt on the carb body had 1 washer on either side and the washer between the carb body and fuel pump hose body was effecting clearance of the hollow bolt. With both washers on the outside of the hollow bolt and the hose plugged it runs again . Still haven't located a replacement restrictor orifice but it is running with the check valve in it's place, although I won't be doing any tuning until I replace this bit.

Based on the emission system diagrams in the manual, my engine only matches up to the 1983 3A-C sold in U.S. and 1983 Canadian 4 speeds. Either 4th gear is broken or this is a 4 speed. Since I have to shift from 3rd gear to 5th. Still not sure about this.

After tuning fuel mix and idle speeds, Next step is to check the front end alignment and try to solve the shaking of the front end going into left hand turns, then hopefully I`ll be ready for paint. I'm debating Olive drab poor man`s paint job as a suitable color.

[xirdneh]

[quote="smokerx"]Based on the emission system diagrams in the manual, my engine only matches up to the 1983 3A-C sold in U.S. and 1983 Canadian 4 speeds. Either 4th gear is broken or this is a 4 speed. Since I have to shift from 3rd gear to 5th. Still not sure about this. [quote]

seems like you should be able to tell if there is too much difference between 3rd and (your maybe) 4th gear
i'm betting your 4th gear is bad
RPM (if you have the gage) should read close to 3000 rpm at 60 mph for a normal 5th gear

[Petros]

Update:
... This either changed something to make it to where I have to plug the hose connecting to the air filter (with the filter off)to get it to run; or the hollow bolt on the carb body had 1 washer on either side and the washer between the carb body and fuel pump hose body was effecting clearance of the hollow bolt. With both washers on the outside of the hollow bolt and the hose plugged it runs again .

I have no idea what you are referring to here, and why it would cause it to act this way. I can not think of why putting washers on one side of a hollow bolt should make any difference, is this the fuel supply inlet banjo bolt? That should not make any difference for anything at all except for causing it to leak fuel. is your float level correct (look at the site glass)?

large vacuum leak perhaps? do you have a vac port wide open? double check the vacuum diagram for your specific car based on the tag in the engine compartment that should say something like "3AC Fed" or "3AC Cal", you can not have both USA and canada emissions package. If you can not match the routing to anything in the manual than likely the routing is all messed up and the cause of your trouble. We need to understand better what is happening. DO NOT RANDOMLY change things looking for a solution, you could make it worse, or make no difference, and you would not be sure what you did. Give us specific details of how it is behaving in all ranges of it running and allow us to help you find the problem. some pictures might be useful too.

[smokerx]

I can not think of why putting washers on one side of a hollow bolt should make any difference,

It was the only thing I changed between two tests. I was hoping it would seat the hole in the banjo bolt into the carb intake better. Gas doesn't leak with the interior washer removed though. Was hoping someone previously installed 2 washers where only 1 was needed.

as far as tags: the door tag is replaced with a junk yard tag that lists it as a 1983. the motor tag is OEM and lists it as a 3A
the hood tag is OEM and lists it as a 3 A-C 4 speed manual transmission. Due to the fact any of these parts could be replacements I don't hold much weight in the tags. The emission system diagrams more closely match the 1983 3A-C engine; definitely does not match the 82 or 83 3A engine.

The engine only runs with the AS air hose capped off or, if not capped, constantly priming it with the throttle pump. tried the idle mix screw at 2 5/8 and 3 turns out. Didn't seem to make a difference. Haven't allowed it to warm up since it smells so rich out of the tail pipe. Checked it for vacuum leaks and can't find any.

[animeracing]

I've actually been trying to get one of these restrictor orifice valves for awhile, they were rather expensive at the dealer (somewhere in the $25-35 range, plus shipping) when they were available.

I still have the (broken) original, it's marked as AISIN with a number 3D27 stamped into it, and the Toyota "TEQ" kanji symbol on the other side.

Peering into it (the ends have broken off), there is just mesh filter material inside - I expect this is what creates the intended restriction.

Other than getting a replacement at the salvage yard, it may be that making one out of a vacuum check valve and some filter material is the way to go.

I'd be interested if anyone can locate one of these or a suitable replacement.

[dlb]

animeracing, which system is the check valve you seek from? there are a few different ones--one for the choke breaker (called a 'jet'), another for the throttle positioner (called a 'VTV'), and one for the manifold vacuum advance (the plain jane 'check valve').

i wonder just how different these things actually are from each other.

[irowiki]

Yeah if you give me the color of it, I can look at my collection.

[animeracing]

animeracing, which system is the check valve you seek from? there are a few different ones--one for the choke breaker (called a 'jet'), another for the throttle positioner (called a 'VTV'), and one for the manifold vacuum advance (the plain jane 'check valve').

i wonder just how different these things actually are from each other.

The one I'm after is the "restrictor orifice" for the choke breaker, #23 on the parts diagram posted previously in this thread;

http://www.nonags.org/members/nijqk/83FedVacR.jpg

the check valve (#21 in the diagram) seems to still be available from Toyota and other sources as it was used on a lot of other vehicles, some fairly recently.


They are different as they perform different functions - a check valve simply allows air to flow in only one direction, so a vacuum can operate, where as the restrictor orifice is just that, a restrictor that has the practical effect of limiting air flow as if it were a smaller tube. My guess would be it works more as a filter than anything else, though it could very well be tuned to restrict a certain amount of air if the previous description of a small metal disc between the filter material is accurate. I'd also guess that a small enough tube could be used in place of the restrictor, though it would lose the filtration ability and probably wouldn't offer the exact amount of restriction as the original, but it may not be that critical.

Yeah if you give me the color of it, I can look at my collection.

Well, when it was new, it was probably clear/opaque plastic, but as its spent its life next to the valve cover, its turned dark brown on one side and yellowish on the other, with a tan cap (that was probably white) that says "AISIN" on one end of the cylinder.

A used one in good condition would be okay, but like the other plastic bits, the heat and age has made most of them brittle and so the ends snap off, which is what happened to the one I have. There are companies that rebuild these carbs so there's for sure got to be a source for these things or whatever they use in place of the originals, I suspect they aren't referred to as "restrictor orifices" though.

[irowiki]

Ah, that is actually a Jet! The one on my various carbs for that specific one is yellow. I'll see if I have a spare. some carbs actually have the "jet" built into that choke breaker port on the carb.

[dlb]

some carbs actually have the "jet" built into that choke breaker port on the carb.

paul's right. i have noticed some of these carbs use a smaller orifice on the carb port for the choke breaker rather than a jet. it accomplishes the same thing since the smaller hole restricts how quickly vacuum builds up to activate the device.

They are different as they perform different functions - a check valve simply allows air to flow in only one direction, so a vacuum can operate,

ah, i think i get it. the VTV only slows the release of vacuum so that the TP slowly closes the throttle (this decreases emissions); the jet slows both the engagement and disengagement of the choke breaker A (not sure why this is necessary though); and the check valve needs to flow only one way because it ties manifold vac and ported vac together to only open the EGR valve when both are present, but keeps the two vacuums from fighting each other during other driving conditions.

btw, i may have a spare jet too. i'll try to check when i get home this evening.

[animeracing]

Ah, that is actually a Jet! The one on my various carbs for that specific one is yellow. I'll see if I have a spare. some carbs actually have the "jet" built into that choke breaker port on the carb.

Well, it does work the same as a jet, but when I mention a "jet" in reference to a carburetor, I'm sure most people would think of the brass and metal replacement jets that are built into the carb.

paul's right. i have noticed some of these carbs use a smaller orifice on the carb port for the choke breaker rather than a jet. it accomplishes the same thing since the smaller hole restricts how quickly vacuum builds up to activate the device.

Probably a newer design improvement on the later models, either the 84-85+ or perhaps the 87-88 wagons. Might even be something that the Canadian and 3A models had and the U.S. and 3A-C models got the plastic restrictor.

Any pics of the carbs with the smaller port? I wonder if this is something that can be modded/upgraded on the carbs that use the plastic restrictor. If there is no filter or anything in-line on that vacuum hose on carbs with that smaller orifice design, maybe a small plastic cylinder with a hole through it the same size as that orifice is all that's needed. Otherwise maybe just removing the carb port from a parts carb and putting it on an older one works - unless it's a port that's built in to the body and not something that can be put on another carb.

ah, i think i get it. the VTV only slows the release of vacuum so that the TP slowly closes the throttle (this decreases emissions); the jet slows both the engagement and disengagement of the choke breaker A (not sure why this is necessary though); and the check valve needs to flow only one way because it ties manifold vac and ported vac together to only open the EGR valve when both are present, but keeps the two vacuums from fighting each other during other driving conditions.

btw, i may have a spare jet too. i'll try to check when i get home this evening.

Based on what Toyota says the choke breaker system does;

The choke breaker system is used to monitor the automatic choke system. To prevent too rich a mixture when the choke is closed, the choke breaker forces the choke valve open slightly. This system performs the same function that the previous one does except that it goes one step further and forces the choke valve to open up even further after the engine has warmed up.

I can see why they'd want it to engage slowly - forcing the choke valve open quickly, even slightly, could have a noticeable effect when driving, and probably cause wear and tear on the parts that move the valve. Making it move slower makes the effect unnoticable to the driver and reduces wear on the parts.