Disconnected thermovalve: impact?

[donbecker1234]

I have dropped my engine (a '79 CA 930) and discovered that the rear thermovalve has it's electrical connector disconnected. The two vac lines are still connected.

I didn't notice any engine issues prior to dropping the engine, but the car is new to me so I might not have noticed. I'm certain I didn't disconnect it during the engine drop.

Does anyone know what impact this being electrically disconnected would have?

I've traced the vac lines, one goes to "additional air valve" and the other goes to a T fitting and then both to the "vacuum limiter" and the "flapper valve".

If anyone could fill me in on it's function that would be great too.

[stevie 77 930]

The thermovalve is used to open the addition air valve during cold starts. The Thermovalve, is open when cold (allowing vacuum to open the addtional air valve). The connection heats up the valve after about 10-20 seconds and closes off the vacuum. Engine heat will also ad to close the thermovalve, so as you have it disconnected, it really doesn't have an effect.

[donbecker1234]

Do you mean that it will still close normally, despite the electrical connection being unplugged?

If so, is there any reason or impact of the electrical connection being unplugged?

[stevie 77 930]

Originally Posted by donbecker1234

Do you mean that it will still close normally, despite the electrical connection being unplugged?

If so, is there any reason or impact of the electrical connection being unplugged?

It will normally close with ambient engine heat.

No impact other than the valve may stay open a bit longer. How are your cold starts ?

FYI ... That connection, is daisy-chained from WUR, AUX AIR VALVE and is on the fuel pump circuit. Make sure it doesnt short out. Might as well plug it in as designed

[boyt911sc]

Originally Posted by stevie 77 930

The thermovalve is used to open the addition air valve during cold starts. The Thermovalve, is open when cold (allowing vacuum to open the addtional air valve). The connection heats up the valve after about 10-20 seconds and closes off the vacuum. Engine heat will also ad to close the thermovalve, so as you have it disconnected, it really doesn't have an effect.

Stevie,

Sorry to disagree and don’t take this personally. This is a Technical forum and we are just discussing how CIS component/s works. A thermovalve is normally closed (engine cold) and when you start the fuel pump, the TV is energized at the same with the AAR AND WUR.

When the thermovalve is energized, the heated disc inside the TV will buckled up and allow the vacuum to passed thru. You got it backward. Go test a thermovalve and find out how it operates.

Tony

[donbecker1234]

Originally Posted by boyt911sc

Stevie,

Sorry to disagree and don’t take this personally. This is a Technical forum and we are just discussing how CIS component/s works. A thermovalve is normally closed (engine cold) and when you start the fuel pump, the TV is energized at the same with the AAR AND WUR.

When the thermovalve is energized, the heated disc inside the TV will buckled up and allow the vacuum to passed thru. You got it backward. Go test a thermovalve and find out how it operates.

Tony

Now I recall having to give the car a little gas pedal when starting it cold, could this be related?

[stevie 77 930]

Tony,

No offense taken... but there are 2 different types of Thermovalves.

If can be confusing, the 930 thermovalve operates opposite of the 911 thermovalve. Here's the bulletin that explains the different valve

[stevie 77 930]

[stevie 77 930]

[boyt911sc]

Originally Posted by donbecker1234

Now I recall having to give the car a little gas pedal when starting it cold, could this be related?

Don,

You don’t need any assistance to start a CIS motor unless something is not right with it. Pressing the pedal accelerator is a common practice for carb engines but not for fuel injection systems. If you are pressing the accelerator to make the motor starts, then there is something inherently wrong with your fuel pressure/s.

Set the gear in neutral and reach for the ignition switch through the open window to start the engine. If you have to get inside the car to make it start, you got a problem.

Tony

[boyt911sc]

Originally Posted by stevie 77 930

Tony,

No offense taken... but there are 2 different types of Thermovalves.

If can be confusing, the 930 thermovalve operates opposite of the 911 thermovalve. Here's the bulletin that explains the different valve

Stevie,

You are indeed correct and I was wrong. Thanks for the technical diagram and literature. Something I have to add to my notes. Need to find a 930 thermovalve for my test collection. Much appreciated.

Tony

[stevie 77 930]

Originally Posted by boyt911sc

Don,

You don’t need any assistance to start a CIS motor unless something is not right with it. Pressing the pedal accelerator is a common practice for carb engines but not for fuel injection systems. If you are pressing the accelerator to make the motor starts, then there is something inherently wrong with your fuel pressure/s.

Set the gear in neutral and reach for the ignition switch through the open window to start the engine. If you have to get inside the car to make it start, you got a problem.

Tony

Agreed

[1979-930]

What is the reason for the engine drop?
Any changes or modifications happening? You can ditch 90% of the 79 hooey if you are making modifications. The decel valve, auxiliary air valve are all emissions related and not needed. The shuttle valve can be replaced with a modern by-pass valve 1/8 the size and complication.
I'm down to a late 80's re-circulation valve and the auxiliary air regulator only.

But if you are restoring the car none of what I said applies.

[donbecker1234]

Originally Posted by 1979-930

What is the reason for the engine drop?
Any changes or modifications happening? You can ditch 90% of the 79 hooey if you are making modifications. The decel valve, auxiliary air valve are all emissions related and not needed. The shuttle valve can be replaced with a modern by-pass valve 1/8 the size and complication.
I'm down to a late 80's re-circulation valve and the auxiliary air regulator only.

But if you are restoring the car none of what I said applies.

Leaking fuel line and years of PO neglect/deferred maintenance. I'm planning on posting a thread soon soliciting feedback from everyone on what I should / shouldn't do and will ping you. Thanks!

[1979-930]

Originally Posted by donbecker1234

Leaking fuel line and years of PO neglect/deferred maintenance. I'm planning on posting a thread soon soliciting feedback from everyone on what I should / shouldn't do and will ping you. Thanks!

Post it in the turbo forum. Lots of guys smarter than I there.