TTV Termal valve 78 SC behavior

[mike sampsel]

My TTV allows vacuum to reach my WUR, not an issue once warm. But maybe it allows vacuum too soon which might explain some of my strange action during "cold" starts.

So if I pull the vacuum line off the WUR, and apply a vacuum pump to that hose/line should it hold vacuum when the TTV is closed? Or is this an improper test?

Mine holds no vacuum after sitting for 2 hours after a 10 sec running of the fuel pump. This is the part I'm talking about.

https://cis911primer.com/pages/comp_page.html#thermvalve

[boyt911sc]

Originally Posted by mike sampsel

My TTV allows vacuum to reach my WUR, not an issue once warm. But maybe it allows vacuum too soon which might explain some of my strange action during "cold" starts.

So if I pull the vacuum line off the WUR, and apply a vacuum pump to that hose/line should it hold vacuum when the TTV is closed? Or is this an improper test?

Mine holds no vacuum after sitting for 2 hours after a 10 sec running of the fuel pump. This is the part I'm talking about.

https://cis911primer.com/pages/comp_page.html#thermvalve

Mike,

Take note that vacuum is coming from the engine (direction of suction). So to test a TTV, you need to apply vacuum to the middle port, NOT at the side port that goes to the WUR. The side port will NOT HOLD VACUUM even on a good working TTV. Repeat your test and apply vacuum to the center port. If it holds vacuum, it is GOOD. If it does not hold vacuum, it means it is leaking and prematurely supplying vacuum to the WUR.

Tony

[mike sampsel]

Thanks Tony,

This morning I removed my TTV and at 88 degrees, neither side would hold any vacuum. At 27 deg F both the center (vacuum from the throttle body) and the outer port on the TTV hold vacuum.

From your experiments (in 2013 I believe) you found the parts held vacuum at 90 degrees F (inner ports only tested?).

I have noted a slight increase in RPM (compared to the vacuum line on?) when I did a cold start with the port at the WUR plugged for a jiffy (no surprise there as the CCP is lower, providing a richer mixture). Wonder if my TTV is supposed to hold off vacuum a tad in my 90 degree garage? Might help explain why my colder cold starts are better behaved.

And another topic: I found there was no whine after 5 day sit with a FULL tank of gas. Interesting phenomenon.