Smoke Machine usage guidance

Hello everyone,

This is my first thread here. I recently purchased an Autool ST206 smoke machine and have a few questions regarding PSI and the usage of the leak detection (air flow meter with ball):

1. This machine can pump up to 15 PSI, but for evap testing, I know it should be less than 1 PSI. What is the maximum pressure I can use for checking intake manifold leaks?

2. For evap testing, I open the air regulator halfway, but the ball in the middle doesn't drop, even though the pressure reaches 1 PSI. I end up shutting down the machine and monitor for pressure drop. Is there another method to check for evap leaks? s only EVAP smoke machine doesn't produce more than 1 psi, so its safe to keep it on until the ball drops or jump up/down.

3. For intake manifold testing, how much pressure can I safely build up? Can I go up to 5 PSI or higher to check for leaks?

4. Is it more effective to pressurize the system with air first and check for pressure drop before performing the smoke test?

Thanks in advance for your help!

The machine I use is not capable of such high pressure, so I cannot say with certainty the maximum pressure you can safely put in the intake manifold of non-forced induction engine, but any time I have smoke tested an intake, it will never hold pressure because there is usually at least one intake valve open, so you likely wouldn't achieve 15psi in the manifold, even if the pump is capable of producing such pressure.
It sounds like there may be a issue with the flow gauge or possible user error if the ball will not drop.
I would set the machine to whatever setting you will use to check EVAP systems and pinch the hose. The pressure should reach whatever you have set it at, and the flow gauge should bottom out.

Edit: I have been alerted to error in my logic. In the event of an open intake valve, the cylinder will fill with smoke,( with high enough pressure the piston meet be moved down in the cylinder) and thus should remained sealed.
Thank you for the heads up Chad!

Thanks for getting back to me. The gauge seems to be working fine, as it drops when I pinch the hose. I was about to ask about the intake, but here's a related situation: we had a similar issue with a customer's vehicle where no pressure was building up. We saw smoke coming out from oxygen sensor (pre cat). We manually rotated the engine slightly, and the smoke almost stopped. This led us to believe there might be a valve leak issue.
Do you think its a valid test to check smoke coming out of exhaust manifold when we pressurize from intake manifold such as brake booster.
or engine with variable valve timings can have such condition where exhaust valve open along with intake valve slightly open.

Do you think its a valid test to check smoke coming out of exhaust manifold when we pressurize from intake manifold such as brake booster.
or engine with variable valve timings can have such condition where exhaust valve open along with intake valve slightly open.

You bring up a good point. Some engines have "Valve Over-lap" where both the intake and the exhaust valves are open at the same time. This would blow smoke right through the intake manifold, into the cylinder, and out the exhaust.

Noah, your logic is not totally flawed. 

 

For evap testing, I open the air regulator halfway, but the ball in the middle doesn't drop, even though the pressure reaches 1 PSI. I end up shutting down the machine and monitor for pressure drop. Is there another method to check for evap leaks? s only EVAP smoke machine doesn't produce more than 1 psi, so its safe to keep it on until the ball drops or jump up/down.

I bought an Autool SDT205S off Amazon several years ago:

shop.autooltech.com/product/autool-sdt20...tor-diagnostic-tool/

Had the same problems your ST906 does. Even when I had the smoke hose capped off and low output pressure, the flow gauge still indicated a leak.   Just couldn't trust it any more. Ended up returning it.

3. For intake manifold testing, how much pressure can I safely build up? Can I go up to 5 PSI or higher to check for leaks?

5 PSI would probably be fine for naturally aspirated engines? More would be good for boosted engines.

My general advice would be to keep in mind the system you're testing and to keep your testing pressure within a reasonable range. Exhaust systems, for example, generally only see a few PSI at the very most. So, if you connect up your smoke machine and crank it up to 15 PSI, you may generate leaks that aren't there under normal conditions. 

Crankcases are the same way. Turn the pressure up high enough, and something is going to leak.