914 smog testing, Whats required in your area? Options

[JeffBowlsby]

I had to smog my DD today and noticed this sign in the waiting room, which would be applicable to the 1976 914s. Tech says they pinch off the evap system (tubing and charcoal filter between the fuel tank and air filter box) and insert some kind of gas under low pressure to test the evap system, for leaks.

What other testing is required in your area, if any?

[jcd914]

The EVAP system pressure test is just looking for leaks in the fuel vapor recover system on your car. In theory the fuel tank is sealed and any vapors from heat or sloshing around are routed through hoses to a charcoal canister. From there they are sucked int the engine and burned, which is good. Raw fuel vapors is not good for the environment, make you garage stink and this system has no negative impact on the way you car runs, it is a win win (IMHO). Typically there are some vacuum and/or computer controls that limit when the fuel vapors are sucked in and that varies from car to car.

The test typically involves clamping the vacuum hose leading from the charcoal canister to the engine and then putting pressure into the fuel tank. They use a gas cap adapter hooked to the tester and I think they use nitrogen. The tank is pressurized and then allowed to sit for a timed period and over that time frame it can't loose too much pressure. I was never able to find any specs on how much pressure is put in the tank or how much it is allowed to loose, the tester figures it out.

Some system were not designed to hold pressure but to passively collect the vapors and this test is not applicable to these car/trucks. Or the testing is just for the tank and the lines/hoses leading to the canister.

I think 914's would fall into that category since the canister is cleared of vapors by the cooling fan blowing air through it and into the air filter.

Since I have not smogged a 914 for a couple decades I have no idea if CA would require this test on a 914.

Jim