Smoke signals

Motor,  Jul 2003  by Marinucci, Dan

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Beware, the origin of a wind or water leak is often far away from wherever the driver thinks he hears it or where he actually sees the water dripping.

Evaporative Emissions Smoke Machines

Within the last 25 years, changing technologies have forced us into more and more advanced test gear. As vehicle systems progressed, we began using digital voltmeters, then scanners, then digital oscilloscopes and so forth.

Likewise, evaporative emissions systems have changed a great deal from the relatively simplistic designs in use when the first smoke machine hit the market in the mid-'90s. Since then, of course, evaps have developed into todays enhanced systems, complete with a trouble code for a .040-inch leak (P0442) and one for a .020-inch leak (P0456)!

The evap evolution has been so rapid within the last eight years that the repair industry is embracing a new version of the general-purpose smoke machine. It's known, aptly enough, as an evap-approved smoke machine. The evap unit is a complete revamp of the existing smoke machine-a night-and-day difference in sophistication and test capabilities.

Remember, an evap machine does anything a general-purpose unit can. But it's also advanced enough to leak-test any evap system safely and accurately. In fact, industry experts now advocate general-purpose smoke machines for everything except evap testing. If you want to test everything including evap systems, they strongly recommend an evap-approved smoke machine. The current crop of evap machines range in price from about $2200 to $3000. Here's what you ought to know about them.

Characteristics of Evap-Approved Equipment

First and foremost, the vehicle manufacturers set the tone here by switching to smoke technology within the last several years. Using an evap-approved smoke machine isn't just recommended, it's now required by DaimlerChrysler, Ford, GM, Land Rover, Saab and Saturn. More approvals are pending.

Predictably, the automakers demanded that evap-approved equipment meet stringent safety, accuracy and performance criteria. In fact, DaimlerChrysler, Ford and GM collaborated with the equipment manufacturers to standardize what "evap-approved" actually means. The result is that you'll get the same, consistent leak test from an aftermaket evap-approved machine as you will from an OE-endorsed unit.

While some automakers use evap smoke machines built specifically for their tool and equipment programs, others require one that's readily available in the aftermarket. Evap-approved smoke machines are available from Champion Engineering in association with SPX/OTC, MotorVac Technologies, Snap-on and Vacutec.

Unlike traditional general-purpose smoke machines, the evap-approved units don't pump their own smoke. Instead, a compressed inert gas source connects to the machine and the gas pushes the smoke where you want it to go.

All vehicle makers but one require inert gas for evap leak-testing. All the companies that supply evap-approved aftermarket smoke machines strongly urge you to always use inert gas for evap leak tests. Nitrogen is the most commonly used inert gas. If you're leak-testing anything other than an evap system, compressed air works fine.