EVAP System testing using a Smoke Machine

Purpose A smoke machine is used to identify leaks in systems that hold and transfer air and vapor.

Usage The primary function of the smoke machine is to test the integrity of the Evaporative Control System The smoke machine can also be used to detect: Intake air system leaks Exhaust system leaks Cabin air/window seal leaks

Other Test Applications Air cleaner assembly Air ducts Air valves Component testing, prior to assembly Diaphragms EGR valve Exhaust manifolds cracks Fuel tank pressure sensor Intercoolers Intake gaskets Injector o-rings Loose clamps Map sensors Mass air flow meter Oil leaks PCV valve and hoses Throttle body shaft Turbochargers Vacuum hoses Vacuum switches

Visible smoke pinpoints the leak source A leak in the vapor recovery system can be easily identified by the presence of smoke at the gas cap

Smoke machine components Smoke oil Large tailpipe plug Smoke dispersal adapter 12 volt power cables UV light source Vacuum pump adapter Wireless remote Exhaust pipe cone adapter UV glasses Plugs Smoke outlet hose Schrader valve removal tool EVAP test port adapter

Smoke oil The smoke machine generates smoke by passing mineral oil over a red hot electric heating coil The oil contains a chemical that glows bright yellow when exposed to Ultra Violet [UV] light

Ultraviolet Light source An LED type UV flashlight is used to pinpoint the source of leaks Condensed smoke oil will glow green/yellow when exposed to UV light

Never look directly into the UV light Exposure to UV light can cause permanent damage to the retinas of your eyes Yellow UV safety glasses should be worn whenever working with UV light sources

Condensed smoke oil Smoke vapor will generally not glow when exposed to UV Light A small amount of smoke vapor will condense around the places that the smoke leaks out of. This liquefied smoke will glow

Check the oil supply A dipstick is attached to the smoke machine’s oil filler cap Unscrew the dipstick and observe the level of oil using the UV light to illuminate the dipstick

Checking the oil Full Mark Smoke oil is a clear liquid so it is difficult to see the level on the dipstick without the aid of UV light

Adding oil If the oil level is low add a few ounces of oil – do not overfill

Connect to the battery The smoke machine is powered by the vehicles battery via the 12 volt power leads at the back of the machine

Hanging the smoke machine When the smoke machine will be used near the engine the machine can be hung from the hood latch Hanging the smoke machine

Air Line coupler The correct type of coupler needs to be installed to connect the smoke machine to the shop’s compressed air hoses

Shop air fitting Compressed air from the shop’s air compressor is used to push the smoke through the system being tested The correct air coupler fitting needs to be attached to the smoke machine

Vapor hose The vapor hose is used to inject smoke into the system being tested

Cone adapters Rubber cones allow the vapor line to connect and seal to a variety of different size and shaped openings The large cone adapter here is used to connect the vapor hose to the exhaust pipe

Plugs Plugs may be needed to seal opening where components have been removed or where a small amount of leakage is expected

Air Diffuser To find air leaks around windows and doors an air diffuser is used to spread out the smoke The vehicle’s HVAC fan is set to high speed while smoke is blown over the edges of the windows and doors Any disturbance in the smoke may indicate an air leak

Adapter for EVAP test port Most late model cars have an EVAP system test port that uses an ACME thread [similar to the fitting on tank of R134a refrigerant.

The EVAP test port is located on the vapor line between the purge solenoid and gas tank The cap is normally a light green color The port is normally located under the hood but is occasionally found underneath the car

Vacuum pump port The auxiliary output port can be used to connect a hand held vacuum pump to the smoke machine Some EVAP systems use electro mechanical vacuum pump located inside the fuel tank to monitor EVAP system integrity A source of vacuum is needed to test the operation of the sensors and pump

Vacuum Pump During the test a small amount vacuum is applied using a hand held vacuum pump

Screen Display

Function select buttons There are 3 membrane switches on the right side of the panel The display select button changes the units of measurement displayed by the 3 digit LCD matrix The orifice select button changes the size of the flow restriction inside the smoke machine The start button starts a 5 minute leak down test and toggles the machine between full flow and pulsed flow

Display Indicator lights When illuminated an ‘Orifice Leak Size’ of .040”, .020” or .010” will be indicated on the LED display When the ‘Flow L/M’ is illuminated the LED displays the smoke flow rate in liters per minute When ‘Pressure in H2O’ is illuminated the LED displays system pressure in inches of water

Display Indicator lights The ‘Vacuum in H2O will only illuminate when the smoke machine senses that the system pressure is lower than ambient atmospheric pressure The ‘Polarity Protect’ indicator will illuminate if the power lead connections at the battery are reversed

Display Indicator lights The ‘Pass’ or ‘Fail’ light will illuminate after a 5 minute leaks test has been completed The three orifice size indicator lights indicate the size the internal restriction in the smoke machines output port

Display Indicator lights The ‘Off/Decay’ light indicates that flow of smoke from the machine is turned off When the ‘On’ light is illuminated there should be a continuous flow of smoke passing through the smoke vapor hose The ‘Low Flow’ indicator light indicates that the machine is operating in pulsed mode. A puff of smoke is sent through the smoke vapor hose every few seconds.

Inches of Water Very low levels of pressure or vacuum are measured in units of inches of water The amount of vacuum applied to the tip of a straw that will cause the water in the straw to rise one inch equals a vacuum level of 1 inch H2O

Inches of water - pressure Pressure can be measured in inches of water using a manometer A ‘U’ shaped glass tube is partially filled with water One end of the tube is open to atmospheric pressure The other end is connected to the pressure being measured The difference between the water levels is measured in inches Pressure source Open to atmosphere

Select the type of gas After the power leads are connected to the battery you have 5 seconds to select the type of gas being used in the test. The default value is ‘AIR’ = shop air If you are using compressed nitrogen gas press ‘Display Select’ until ‘n2’ is displayed If you are using compressed carbon dioxide press ‘Display Select’ until ‘CO2’ is displayed

Select the display type Pressing the ‘Display select button cycles through the three types of data displays: Orifice Size Flow rate Pressure / Vacuum If you are performing a pass/fail leak test the display must be set to orifice size to finish the test When the display is set to pressure the vacuum LED will illuminate if the system pressure is below the ambient atmospheric pressure

Start button functions Pressing the ‘Start’ button will begin sending a steady stream of smoke through the smoke/vapor hose This begins a timed 5 minute test of the EVAP system Pressing the ‘ Start’ button a second time will set the smoke machine to pulsed low flow mode While in ‘Low Flow’ mode the smoke machine will make a clicking noise

Turning off the machine The machine will automatically shut down after the completion of the 5 minute test or after 8 minutes of inactivity Holding the ‘Start’ button depressed for a few seconds will force the machine into shutdown mode

Low battery voltage warning Lo bAt A ‘Lo bAt’ warning message will be displayed if the battery voltage level is below 11.0 volts

Remote start/stop The smoke machine comes with a remote key fob that is used to start and stop the flow of smoke

Max Pressure and Flow Rate Maximum smoke pressure = 13.0 inches of H20 Maximum flow rate = 10 liters per minute

Pressure release valve OBDII EVAP System EVAP test port Purge Solenoid Vent Solenoid Charcoal canister Intake manifold Sealed gas cap EVAP Pressure sensor Roll over valve Pressure release valve Fill limit vent valve

Canister and vent solenoid The charcoal canister and vent solenoid are located under the vehicle and within a few inches of the fuel tank Vent to atmosphere Charcoal canister Vapor line to tank Vent solenoid Purge line

Purge line connects to canister Purge solenoid Purge line connects to canister The purge solenoid controls the rate at which gasoline vapors are removed from the canister during the drive cycle It is normally found under the hood

EVAP Monitor All OBDII systems run a non-continuous monitor on the evaporative emissions system at least once in every trip There are two test performed in the EVAP system monitor: A system integrity [leak] test A system performance test [flow test]

EVAP Monitor If either test fails in two consecutive trips the Check engine light will illuminate and a code will be set EVAP system codes range from P0440 through PO470

EVAP System integrity test phase 1 Purge Solenoid - open Vent Solenoid - closed EVAP Pressure sensor During the first phase of the test the PCM commands the vent solenoid closed and pulses the purge solenoid to create a partial vacuum within the tank

EVAP System integrity test [leak test] After enabling criteria are met the PCM commands the canister vent solenoid closed and sends a PWM current [pulse width modulated] to the purge solenoid to allow a small partial vacuum to build up inside the gas tank When the pressure inside the tank reaches a preset amount – typically around 10 inches of water – the purge valve is commanded closed Pressure inside the tank is monitored for the next few minutes

EVAP System integrity test phase 2 Purge Solenoid - closed Vent Solenoid - closed EVAP Pressure sensor When the pressure sensor reaches a preset value the PCM closes the purge solenoid. The vent solenoid remains closed. The PCM monitors the change in pressure inside the tank for the next few minutes.

EVAP monitor – system integrity test If there is a rapid rise in tank pressure after the purge solenoid closes there must be a large leak – greater than .040” . The EVAP integrity test fails. If the tank pressure slowly rises over a period of several minutes the total leak size must be smaller than .020”. The EVAP integrity test passes. The EVAP monitor then begins the system flow test.

EVAP monitor – flow test Purge Solenoid - cycling Vent Solenoid - open Upstream oxygen sensor The flow test looks at the changes in short term fuel trim as the duty cycle applied to the purge solenoid is altered by the PCM.

EVAP monitor – flow test During the flow test the canister vent solenoid is open and the duty cycle [PWM] applied to the purge solenoid is slowly increased until it reaches 100% open. The PCM looks at 3 factors: Short term fuel trim [STFT] Idle rpm IAC or Electronic throttle control idle position If any of these factors change significantly as the duty cycle on the purge solenoid is increased the EVAP monitor passes

Troubleshooting EVAP system leaks If the check engine light is illuminated and a scan tool reveals a code for an EVAP system leak the smoke machine is the best tool to locate the source of the leak. A scan tool may be required to actuate the canister vent solenoid to the closed position. Leave the scan tool connected after verifying the code

Remove Schrader valve Before connecting the smoke machine to the test post remove the Schrader valve The Schrader valve has left hand threads – turn the tool clockwise to loosen it

Install the test port adapter Thread the end of the adapter on to the test port Hand tight only --- Do not over-tighten

Connect the smoke hose The smoke hose is connect by pushing the cone shaped hose end into the adapter hose

Setup smoke machine Connect the smoke machine to shop air [or CO2, N2 if available] Connect the electrical leads to the battery – check that the polarity indicator is not illuminated

Go to Scan tool In the scan tool menu find the test menu for functional test

Scan tool EVAP test menu Find the EVAP test that allows the scan tool to open and close the canister vent solenoid

Scan tool EVAP test menu Select vent solenoid (on/off)

Scan tool EVAP test menu Use the Y/N buttons to toggle the vent solenoid on and off

Scan tool – tank pressure sensor The scan tool page here displays the tank pressure in inches of mercury To convert inches of mercury to inches of water multiply by 13.5 The pressure measured here is 9.86 inches of water

Select the orifice size Press the orifice size button until the correct orifice size is displayed: .020” for vehicle built after MY 2000 .040 for built between MY 1995 and 1999

Start 5 minute test Press the Start button to begin the 5 minute test You can change the display to pressure H20 or flow L/M during the test but the display must be returned to orifice size to get the pass/fail indicators to function at the end of the test

Check for evidence of smoke leakage During the test raise the vehicle to examine all of the components of the EVAP system for evidence of leakage The vent solenoid shown here is frozen in the open position

Check the gas cap seal Open the fuel filler door to check the condition of the cap seal

Pass / fail indicators If there are any leaks detected the fail indicator light should illuminate at the end of the test The off/decay light should also be on to indicate that the flow of smoke has been turned off

Small leaks Leaks that are too small to release visible smoke may be detected by shining the UV light along the hoses and around the canister. Condensed smoke oil should glow green/yellow around any small leaks

Finding exhaust system leaks A spare battery or jump box can be used to power the smoke machine

Cone adapter for exhaust If the vehicle has dual exhaust with a crossover one tailpipe may need to be plugged

Muffler drain Many mufflers have a condensation drain hole near the bottom Smoke coming out of the drain shown here is normal Seal the drain hole with a piece of tape to prevent the smoke from the drain masking any other exhaust leaks

Exhaust flex joint Pay special attention to the flex joint in the exhaust where the front pipe connects to the exhaust manifold. Shine the UV light onto the exhaust manifold to detect small cracks

Finding intake leaks Since the throttle plate never closes completely you will need to plug the intake upstream of the throttle plate.

Connect smoke hose to manifold There are normally several manifold taps that you can connect to Canister purge solenoid Smoke hose Vacuum supply line For this vehicle we disconnected the vacuum supply line for the purge solenoid

Distorted throttle body gasket Find the leaks When smoke is introduced into the manifold even very small air leaks will emit smoke Distorted throttle body gasket

Other uses The smoke machine is not limited to on car testing. The seals and gaskets of a rebuilt engine can be smoke tested prior to installation If you can figure out a way to seal off the open areas of the system you can smoke test almost anything