smoke test on the wife's car.

My wife's 2004 Trailblazer keeps coming up with an evap leak code. So I picked up a paint can drilled a couple of holes in the top, connected the air compressor with a hose and stuck a cigar in the other hole. I connected the hose to the brake booster port on the manifold and put a rubber glove over the throttle body. My first problem was that the cigar would not generate enough smoke for me to see any leaks. Tomorrow I am going to try charcoal and cardboard. Think that should be enough smoke. My big problem was that the glove on the throttle body was blowing up like a balloon. (It looked like Howie Mandle's stand up routine.) I don't know if I was putting too much air in the system or if there is another was to seal it up. Every time I released air from the system the glove would go down.

I was told my an aeronautical engineer who worked on McDonnell Douglas's fighter programs that back in the 50s they tested cockpit seals with a coffee can filled with pipe tobacco. Maybe shred the cigar and light the resulting pile?

I'm thinking you want very low pressure through the hose - just enough to raise the internals slightly over ambient and keep the fuel at a slow, smoky burn.

Thanks. I will give that a try.

Would one of those bee smoker things work?

also I would think that you would want to fill up the manifold with smoke first then seal it off and add more cresting the pressure.

A cigar is wrapped too tightly to burn without air being drawn through it

Sage Grass.

FWIW, I think you are looking in the wrong spot. An EVAP leak code would be generated by the tank, the hoses between the tank and the vapor cannisters, and the lines connecting that to the engine.

The code is generally set by closing all of the valves, then letting the engine draw a slight vacuum on it, closing the valves, and check how fast that vacuum draws down. If it can't hold a vacuum, well, there's a leak.

Isnt there a TSB or recall regarding the gas tanks on these things? Something about spilling fuel at the filler neck...

Maybe I am remembering this wrong.

http://forums.trailvoy.com/showthread.php?t=100346

This should get you going.

Good Luck!

Rob R.

The engine intake has very little to do with EVAP except for the vacuum.

There is a solenoid valve that controls things and the line to the canister etc. these are what needs to be checked.

can you get a hold of a fog machine?

Have you got a quote for a smoke test from a shop? We used to do it for around $50. Its okay to do that stuff sometimes.

Like mentioned, you need to go straight to the tank system for testing. DO NOT USE COMPRESSED AIR ABOVE 2-3 PSI! Horrible things may/will happen when pressurizing a fuel tank that much.

I don't think smoke created by any type of fire is a good suggestion either. These are gas fumes you are playing with here after all.

I have successfully used a Halloween smoke machine to work as a smoke tester before.

Isn't a lot of the evap stuff on modern cars back by the tank anyway?

In reply to mazdeuce: Yes. There is usually the Evap Purge valve under the hood that controls the gas vapor venting in to the intake (which can be removed and just blow through it to test if it leaks.default is closed until electronically controlled open).
The Vent valve, charcoal canister, and leak detection pumps are usually located right next to the tank under the vehicle or in the wheel well.

Looks like there is a TSB for small leaks at the fuel filler neck.

Thanks. I have been on trailvoy and gmnation for the trailblazer. I missed the TSB on the filler neck. I thought that because it vents into the intake I would be able to check the whole vacuum system. I don't want to aply an open flame to the gas tank. I think the charcoal canister is under the car on the frame, not the best design. I might have to start there. The only shop in the neighborhood I trust doesn't have a smoke machine.

I sorta wonder if those e-cigarette things can be used as a cheap smoke machine.

Seems like they could be coerced to make the right kind of fog, but I wonder if it's enough?

my montana is throwing an evap leak code. its the filler line from the gas cap to the tank. i've heard those are one of the most common issues with GMs for throwing an EVAP light

I've seen using a cigar and blowing the smoke directly from the mouth into a vacuum source.

Let me as Monica Lewinski, I'll get back to ya.

Just saw this DIY Smoke Generator.

Found a shop to do a smoke test. The fuel tank had a crack at the inlet hose. GM repaired the extended wheel base models but not the standard wheel base. No one had a new gas tank in the area, which was good because a new tank is around 1000.00. I found a bone yard with one for 125.00. Of course that one had the same crack. Then I found another yard the shop deals with. They quoted me 400.00. I had the shop call and I got it for 100.00. I will see if anymore codes pop up this week. I already replaced the vent valve and purge valve. If everything reads clear I will take it for the emissions test and then I can get me new plate sticker.

Cone_Junkie wrote: Looks like there is a TSB for small leaks at the fuel filler neck.

The filler necks leak, the fuel caps wear out, the vent solenoid gets dirt in it and fails to seal properly, the sending unit rusts through...

There isn't one sure thing. "Evap code" is also pretty nebulous, there are a bunch of 'em.

would it throw an "evap code" if you continually over fill the tank, squeezing every last drop you can at fill up ?

I remember when I bought my Integra they told me not to do this … because it would cause a CEL, from gas sloshing over into the charcoal … I was welcome to 1 free fix … (while under warranty) …

I sold the car a couple of months ago .. the new owner told me that it's thrown a "evap code" and his buddy is going to do a smoke test …

all the above info (about the tank) is good … I'll let him know

wbjones wrote: would it throw an "evap code" if you continually over fill the tank, squeezing every last drop you can at fill up ?

Solid maybe. It won't affect the tests themselves, as they will not run within 15% of empty or totally full. However, if you manage to get liquid gasoline into the charcoal canister, that can break the charcoal down, and if/when it gets sucked into the engine through the purge solenoid, some of it can prevent that from sealing properly.

Modern fuel systems are generally pretty well designed as far as preventing fuel from sloshing into the evap lines. Generally. Honda and Hyundai still haven't really figured it out.