Thermo valve

http://members.rennlist.com/jimwms/CIS/vaclines_78.gif

More info here: http://members.rennlist.com/jimwms/CIS/CIShome.html

I'll have to look around for an O-Ring kit.

So I guess it adjusts the reference atmospheric press based on ? Is the electrical component another bimetal controlled diaphram or something?

From Jim Williams' site:

Thermo Valve

Holds off vacuum from the warm-up regulator when engine is started cold ('77 - '79 engines). Power is applied to the thermal valve when engine is started, and approximately 30 seconds later, the valve opens. When the valve is open, vacuum to the WUR is then determined by the intake manifold. --The vacuum holdoff results in a mixture richening at warmup. The inner hose connects to the intake vacuum source and the outer hose to the WUR.

But shouldn't this be an atmosphere reference? The other side of the diaphram is referencing the intake vacuum???

Sorry, I think I screwed up with the two diagrams and my initial response. From what I have read the 78 WUR switched the vacuum and atmosphere connections. So, the first diagram I posted is actually a pre-78 WUR and the second, with routing, is correct for a 78. So, for the 78 you should have vacuum (by way of the Thermal Valve) to the bottom and atmosphere on top of the WUR.

i did the same thing, i forget they changed the atmosphere and vacuum connections in 78. the vacuum is on the bottom side and the atmosphere is on top. the 77 had the vacuum on top. i appologise for the bad info.
if u have vacuum to the WUR and your pressure is still low, the bimetal spring is not bending up enough to allow the other spring to raise and increase the pressure. i think the bimetal springs just get tired and dont do what they are suppose to do, or the heater does not get it hot enough to bend up far enough. if the vaucuum enrichment does not work, you dont get the extra burst of fuel needed like the pump a carb supplies when you press the gas pedal.
the TTV is only there for cold start-up. it blocks the vacuum to the WUR when cold to make it even more rich. i have mine bypassed right now and i dont miss it. once again, sorry for the mix up of the vacuum line.

So where does the atmosphere ref go. From memory it seems to be around the throttle body. So is the atmos ref really the press between the plate and the throttle body?

I made a new o-ring and put it back together. The upper chamber (where bimetal arm is) still does not hold vacuum. I am quite confident that the o-ring seal is good. So what is going on? Is it supposed to hold a vac? (remember 78 so it's different). The only other seal is the diaphram that controls the fuel flow ( has fuel on one side air on other). But if that was leaking the chamber would be full of fuel and it was dry.

Lower chamber below spring and diaphram holds good vac.

SO three seals associated with the inner chamber are good. SO why no vac? Maybe it has a vent???? If it's teh atmosphere ref that could be????
Anybody else have a 78 and can definetively say that the main chamber (top vac port) holds vac?

Jim Williams says in part:

Old style regulators can be replaced with newer ones, placing a piece of tubing over the vacuum connection and leaving it open, pointing down to avoid trash. The internal vacuum diaphragm(s) can leak; check this with a vacuum pump. The diaphragms shouldn't leak over 2 " vacuum in 15 seconds.

Have you tried to run with vacuum left open?

Just thinking about it makes me wonder why vacuum is needed in the upper chamber since the bi-metal spring, and coil valve springs, control the fuel supply.
If there is a reason, I would like to know what effect vacuum would have on the function of the WUR.

gunter,
i ran a lot of tests on my 3 yr old WUR.

cold no vac : .8bar
cold with vac: 1.8bar
hot wth no vac: 2.9bar
hot with vac: 3.6bar

this for a 77, vacuum connection on top. when the vac is applied it lifts the diaphrgm that the smaller spring is on thus increasing pressure. there is also an allen adjustment that changes the tension on the small spring. i have wondered if the allen will change how the vacuum enrichment reacts ( ie more or less sensitive to vacuum changes) without affecting the ovrfall pressure? hope the numbers help

So now I'm not clear. Should my 78 WUR hold vac in the main chamber (where springs-bimetal arm are)?

WUR....
 

Adam,

Its been a while since I kept following this thread. What's the number on your WUR? It should have like 0-438-140-045 stamped on the body.

So right now what's the problem do you have that's taking it too long to solve? I have a spare WUR (loaner) if you need to test it.

Merry X'mas and Happy holidays......

Tony

Thanks Tony! that's super helpful but I think the WUR is good.
I just came back from playing with it in the barn ( the WUR ,minds out of the gutter).
I vac checked all chambers int eh WUR and everything is good. I did it by hooking a hose up to one port and then submerging the hose and blowing into another. All chamebrs are air tight. So I put it back on the car and then bypassed the thermo vale to see if that was stuck. Didn't make a difference so I guess thermo vavle is o.k. It still stuttered under load when cold but seemed to clear up quicker than before. So basically I would say that WUR is o.k. now and there is another problem in addition to the WUR not being air tight before.
So the to date diagnosis has revealed.

WUR is o.k. presures hot and cold and diaphrams are good.
Auxiliary air regulator is good.
Thermo valve is good
No vac leaks. RPM drops when I pull oil tank cap.
Fuel dist and associated comp seem to be good.

Runs great warm. Start right up but when cold pops stutters when throttle is hit.
?????????????????????

Also forgot. Pulled two fuel inj to see if they were spraying well. Both looked good. I assume this is also indicative of others. Maybe check later if necessary.

what were your cold pressures again?
check it with the engine off then again when u first start it. just to verify the vacuum circuit, remove it with the car running or use a vacuum pump, the pressure should change.
have u had the mixture checked with a gas analyzer? is the vacuum to the WUR connected to the right place on the TB?

subscribe