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Foxtrot · 12-19-2016, 07:29 PM

While replacing the water pump on my truck last night, I broke what appears to be a Thermal Vacuum Switch for the Early Fuel Evaporation system. It was a brittle plastic, spark plug looking thing with four vacuum hoses running to it pretty close to the thermostat housing. At least one hose runs to the carb.

I'm having a really hard time finding a vacuum diagram that looks like it goes to the truck or any sorts of manuals that talk about servicing or parts for this system.

Assuming this is the EFE TVS, what's happening without it operating? Haven't noticed the truck running any differently (other than a bit cooler, which makes sense with a new pump and no rad leaks).

My main concern is that when I go to look up a replacement EFE TVS, the only ones listed on O'Reilly, Autozone, Advanced, etc. have only two hose connectors.

This is a '79 Silverado Camper Special with a 7.4L.

12-19-2016, 07:29 PM	#1
Foxtrot Registered User Join Date: Dec 2016 Location: Tacoma, WA Posts: 17	Broken Vacuum Part (Thermal Vac. Switch) While replacing the water pump on my truck last night, I broke what appears to be a Thermal Vacuum Switch for the Early Fuel Evaporation system. It was a brittle plastic, spark plug looking thing with four vacuum hoses running to it pretty close to the thermostat housing. At least one hose runs to the carb. I'm having a really hard time finding a vacuum diagram that looks like it goes to the truck or any sorts of manuals that talk about servicing or parts for this system. Assuming this is the EFE TVS, what's happening without it operating? Haven't noticed the truck running any differently (other than a bit cooler, which makes sense with a new pump and no rad leaks). My main concern is that when I go to look up a replacement EFE TVS, the only ones listed on O'Reilly, Autozone, Advanced, etc. have only two hose connectors. This is a '79 Silverado Camper Special with a 7.4L.