Author Topic: Let's make a simple EVAP smoke machine for under $20  (Read 198 times)

Offline goodfellow

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Let's make a simple EVAP smoke machine for under $20
« on: March 13, 2019, 05:23:10 PM »
I was in need for a smoke machine to help a buddy out and chase down an EVAP problem . We spent most of yesterday morning using this machine to finally pinpoint a leaking purge solenoid in his truck. It worked real well --

Here's how I did it. Picked up a Halloween style Chauvet DJ smoke generator from the Goodwill store for $8. These things are cheap  -- and are all over ebay for just a few bucks.





Taking the cover off revealed a fluid reservoir a solenoid pump (for the fluid pipe),



........and a smoke generator (basically a small boiler with a cutoff switch)









Nothing here needs to be modified --  the smoke generator heats up to a specific temperature and then a small amount of fluid (basically a glycerin base mixed with water) is pumped into the hot generator -- creating steam and smoke which is released through a small orifice in the smoke generator. The steam provides the velocity for the smoke when released through that small orifice. This accounts for the pressure of the smoke as it is release into the atmosphere through a diffuser built into the smoke machine case.

I removed the smoke generator (boiler) and took the unit apart.





Boiler (smoke generator) with the release orifice on the right side.



Once removed from its housing, you can clearly see the small orifice tube on the right hand side boiler. What I needed to do was harness the smoke/steam mix from that orifice and make it useful for smoke testing. By itself, the steam/glycerin mix is very hot when it exists the orifice and being mostly steam, it condenses very quickly -- and dissipates. Not good  for smoke testing. We want the smoke (the glycerin part of the mix), but not as much steam (the water part of the mix).

To do that, I needed to have a way for much of the water to condense quickly before it enters the hose with the glycerin smoke. The solution is a small venturi made up of a cheap 1/8 FIP compression "T" fitting.

I drilled out the original smoke diffuser on the machine housing just enough to allow the "T" fitting to slip through. Then i attached the "T" fitting to the housing with one of the compression nuts that came with the fitting -- this will allow the small boiler orifice to sit inside one leg of the "T fitting when it is mounted back in place.





Then I scrounged the parts bin for an adapter to attach to the "T" fitting -- unfortunately nothing fit. No problem -- take an existing 1/4" NPT to 1/8 FIP female brass reducer and drill out the 1/8" side to 7/32" and re-thread with a 12x1.5 metric tap to make a custom connector. Then just attach a standard 1/4" NPT hose barb on the other side of this custom made reducer. Here's what it looks like -- from left to right -- 1/4" NPT barb, cutom reducer, and "T" compression fitting screwed into the housing of the machine.



For the venturi, I used one another of the "T" compression fitting nuts and one of the barbs that was in also in the "T" fitting kit, and tightly screwed the assembly on top of the "T" fitting ...





Notice, that I crimped the barb closed on top, but it sits loose under the compression nut. Now, when the boiler vents its steam/glycerin mixture, much of the water is instantly condensed at the venturi and bubbles up through the fitting. I now have more smoke than steam in the hose.

Put the unit back together, and plug it in. Within a minute or two I can press the remote control button and a nice flow of smoke comes out. It's still hot steam, but not as wet as before; hence less water in the line and more smoke through the hose.



I attached a six foot 5/16" vacuum hose to the "T" barb, and installed a tapered fitting on the other end of the hose.



Nice cool smoke ..... venturi works!



The project is easy to do and takes a few hours to test and get all the hardware together. It's a good solid workaround than those stinky DIY paint can and mineral oil units that are so popular on YouTube.

The machine cost $8.00, and the 1/8" FIP compression "T" (which includes 3 compression nuts, and 3 small compression barbs) was $7.85, add in the 6' vacuum hose for $4.00 and the whole thing was about $20.00 (this doesn't include the fluid that I purchased at Walmart for $7.00)

As I said, we used it to troubleshoot a purge solenoid and it worked better than expected -- lots of cool smoke. That said, this thing can't be run continuously like the $1000 dollar professional machines, but even when run intermittently, we produced a LOT of smoke with this thing.

IMPORTANT:

LAST NOTE -- If you plan on setting up a similar machine, please make a note to drain and flush it after every use. Drain and flush the tank with distilled water, and then run the machine with clean distilled water for several cycles to flush out the glycerin residue in the boiler tubes.

DO NOT .....let the water/glycerin smoke solution sit in the tank -- it will separate and clog up your pump and your boiler tubes.


« Last Edit: March 17, 2019, 01:34:34 PM by goodfellow »

Offline m_fumich

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Re: Let's make a simple EVAP smoke machine for under $20
« Reply #1 on: March 15, 2019, 10:24:02 AM »
I had to Google what an EVAP purge solenoid did to understand how the smoke helped. While I figured that out, I donít understand how youíd tap into that system to make sure the entire system would be tested or were you expecting to test multiple parts of the system individually? I understand what the purge solenoid does, I donít understand how a leaking solenoid would cause a malfunction. I just donít understand that entire system. What else might the smoke machine be used for? Great modification BTW.


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Offline goodfellow

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Re: Let's make a simple EVAP smoke machine for under $20
« Reply #2 on: March 15, 2019, 10:53:58 AM »
I had to Google what an EVAP purge solenoid did to understand how the smoke helped. While I figured that out, I donít understand how youíd tap into that system to make sure the entire system would be tested or were you expecting to test multiple parts of the system individually? I understand what the purge solenoid does, I donít understand how a leaking solenoid would cause a malfunction. I just donít understand that entire system. What else might the smoke machine be used for? Great modification BTW.


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Instead of typing a long screed about EVAP testing, I'll link to a good vid about the usage of these smoke machines. There are literally dozens of good YouTube vids concerning this subject.





Offline stokester

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Re: Let's make a simple EVAP smoke machine for under $20
« Reply #3 on: March 15, 2019, 02:27:24 PM »
Good on ya Ray, I don't know how you would find some of the problems in an EVAP system without one.  I spent many hours using the Kent-Moore nitrogen smoke machine chasing down an elusive leak, they can be difficult to find many times.

For most folks a P0442, small leak, the first thing to do is ensure the gas cap is fastened properly.  If we found a locking cap, it was replaced and it was testing using nitrogen to pressurize the system because many are quite cheap and don't seal properly.

Along with the purge solenoid, the vent valve was a frequent culprit on the Suburbans, Tahoes and Silverados.

Were you able to seal the system using your scan tool?

While there are many drivers who will leave things alone if it is just an EVAP code it is not a good idea.  With the CEL on it will mask any further issues, possibly serious that may arise, a misfire or lean condition comes to mind.
Nick
Yorktown, VA

Offline goodfellow

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Re: Let's make a simple EVAP smoke machine for under $20
« Reply #4 on: March 15, 2019, 02:34:42 PM »
Good on ya Ray, I don't know how you would find some of the problems in an EVAP system without one.  I spent many hours using the Kent-Moore nitrogen smoke machine chasing down an elusive leak, they can be difficult to find many times.

For most folks a P0442, small leak, the first thing to do is ensure the gas cap is fastened properly.  If we found a locking cap, it was replaced and it was testing using nitrogen to pressurize the system because many are quite cheap and don't seal properly.

Along with the purge solenoid, the vent valve was a frequent culprit on the Suburbans, Tahoes and Silverados.

Were you able to seal the system using your scan tool?

While there are many drivers who will leave things alone if it is just an EVAP code it is not a good idea.  With the CEL on it will mask any further issues, possibly serious that may arise, a misfire or lean condition comes to mind.

Thanks Nick -- yeah, it's a good tool to have when things get weird with the EVAP codes. I don't have a scanner sophisticated enough for bi-directional control to seal the system, so we just blocked it off at the hose with a pair of clamping pliers. In our case it was a serious leak -- the housing had a crack, and was leaking smoke like crazy.

Offline Heiny57

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Re: Let's make a simple EVAP smoke machine for under $20
« Reply #5 on: March 15, 2019, 06:44:36 PM »
Pretty cool deal.
MAGA

If you canít fix it with a hammer, it must be electrical.