How To Smoke Test For EVAP Leaks
HOW TO SMOKE TEST FOR EVAP LEAKS
Recommended Tools:
- AutoLine Pro Automotive Smoke Machine
- Your choice of one of the tools below to access the EVAP System.
This is another step that sounds so easy until you try it. We recommend testing indoors in good light where there is not a breeze. Get a good, very strong flashlight. Using a laser pointer can help detect tiny amounts of smoke. Make sure that the smoke machine does not run out of smoke during the testing process. Always use a smoke machine that limits the applied pressure! Our AutoLine Pro Shop Series smoke machine is a powerful, yet budget friendly solution recommended for both veteran and DIY mechanics alike. Whichever smoke machine you decide to use, you will more than likely need to pick up an EVAP Service Port Adapter or Gas Cap Adapter to properly access the and smoke test the EVAP system.
ATTACH THE SMOKE SOURCE TO THE EVAP PORT
Locate the access port for the EVAP system under the hood of the car. The port is covered by a green plastic cap which simply unscrews. There is a valve core under the cap, but the smoke machine should be able to push smoke right past it.
If the vehicle does not have a test port, you can connect to the tank via the fuel filler using the appropriate adapter. Again, fill with smoke and check for leaks.
A NOTE ABOUT SMOKE TESTING AND PRESSURE
EVAP systems are designed to operate and test at a very low pressure of about 12 inches of water – that is about one-half PSI. Testing them at pressures above 7 psi could blow off hoses or damage the pressure sensor. Always use a smoke machine that regulates that applied pressure to less than 7 psi.
WHAT TO DO ONCE YOU FIND THE LEAK
So, what’s leaking? If you are having a hard time pinpointing the leak, you may have to remove the rear seat or even drop down the gas tank for closer examination.
Don’t forget to replace all parts that are questionable. We’ve seen rust on the retaining ring of the fuel pump cause the pump housing to crack and create a leak.
REPLACEMENT PARTS
You have several choices for EVAP system parts. Consider the amount of work to replace a defective part before you make a purchase decision based on price alone.
“The Dealer” is the source that generally offers the highest quality (OE), highest price replacement parts. Many aftermarket parts perform or even outperform OE parts for a lower price. However, some part makers sacrifice quality for price, and you will end up paying the cost. Personally, my rule of thumb is that if it takes more than two hours to change the part, I am buying it from the dealer or a reliable parts source such as Rock Auto (not a sponsor).
Easy access parts can be located by searching for the lowest cost on sites such as eBay motors. Local parts vendors such as AutoZone, Parts Plus, NAPA, and O’Reilly often have quality parts at competitive prices.
WRAPPING UP THE JOB
CLEAR DTCS AND RETEST
After repairing the system, clear the DTCs using your scan tool or code reader. You can also clear codes by disconnecting the negative battery terminal for ten seconds, but you may have to reset clocks, radio stations, and other presets if you do it this way. Either way should turn the MIL off.
Whichever way you clear the codes, the computer will have to run its self-tests (called Monitors) before it is happy that the system is working properly. This can take a few weeks of driving for some cars.
Click here if you would like to learn more about troubleshooting DTC codes.