Oooh the pressure!

**Joe Rappa** · 04-07-2011, 08:56 AM

Originally posted by Trindaddy

Hello again my friends. Just a quick question for you all tonight. More than once i have had an issue using the eeld smoke machine to test a GM product using pressure as opposed to vacuum. Today a GMC Sonoma had Lyle and I scratching our heads. It came in with a small leak code so we gave it the full evap test. What we found was no leakage at all. However, we could not see the release of pressure by opening the vent. After multiple times of putting our own tube to our mouth and the vent, it became apparent that the vent worked fine but would stick closed if it was shut under pressure. If closed while sucking (yes with my mouth), it worked fine. Has anyone else noticed this? How do you guys test this system using the eeld type "pressure tester" like we have? Is this just a weak solenoid or is this a noted issue with GMs (and perhaps others) with these kinds of testers?

Neil

Hi Neil,
Yes. This is normal. Many cars have vents that will be held closed by pressure in the EVAP System. I just relieve the pressure by opening the gas cap for a moment, or by pulling the smoke machine hose off...whichever is easier.

Joe

**Trindaddy** · 04-09-2011, 03:37 PM

Good, i think we made the right call. We had a small leak code we could not duplicate (no flow w/ eeld). The gas cap gasket was rotted and cracked so we replaced and sent it home. We weren't sure about the vent so we left it alone. As you indicated, it seemed to be working correctly. Thanks again Joe.

Neil

**greasybob** · 04-09-2011, 04:23 PM

I hate to give this advice, but in the past when presented with a small leak code on a Chrysler with LDP or NVLD, after making sure a purge vapors test worked, All I would do is crimp off the vent line from the NVLD or leak detection pump and smoke it and check for flow on the gage. If there were no leaks found I replaced the NVLD. I have to say it was a pretty effective way of diagnosing and fixing the problem. OK now you can chew me out for not doing a proper procedure. Now that I got the Smart Smoker I promise to change my ways.

**greasybob** · 04-09-2011, 04:29 PM

I should add that I've taken a lot of the NVLDs that I replaced apart and always find them full of dust and dirt. Maybe thats what keeps them from sealing up ?

**Joe Rappa** · 04-09-2011, 07:27 PM

Bob. Next time you want to check the NVLD, please try this:
From the Functional Test Menu, turn the Purge Valve on. Make sure you have the NVLD PID on screen when you do. When you start ramping the purge valve up the NVLD Switch should close. If not, it's bad.
In some cases you can't turn the purge valve on and view the PID at the same time. When that happens, just wait for the purge valve to turn on. If it's clicking, with the engine running, the NVLD or ESIM Switch should be closed.

On NVLD and ESIM Systems (the new Chrysler stuff), I perform this check first, then smoke it to check for leaks. You have to close the vent mechanically (by plugging/pinching it off) because there is no way to seal these systems like most others.

Joe

Attached Files

**greasybob** · 04-30-2011, 04:15 PM

OK, Joe, I think I figured out a way to check the NVLD functionality with a hand held vacuum pump, my Verus and my Super smoker. I tried a few other techniques as well but because the necessary scan data pids were missing and you can't do function tests with the engine running, this worked best. Not the greatest video but I think you'll get the idea. I'll post the failed attempts later. http://www.youtube.com/watch?v=a3KIl3gNNAs

**Joe Rappa** · 04-30-2011, 06:44 PM

Originally posted by greasybob

OK, Joe, I think I figured out a way to check the NVLD functionality with a hand held vacuum pump, my Verus and my Super smoker. I tried a few other techniques as well but because the necessary scan data pids were missing and you can't do function tests with the engine running, this worked best. Not the greatest video but I think you'll get the idea. I'll post the failed attempts later. http://www.youtube.com/watch?v=a3KIl3gNNAs

Nice job Bob. You tested the same way I do. It's quick and effective. You can also just hold the car at high idle and watch for the purge valve to open. As soon as it hits around 25% or so (if I remember correctly) the NVLD or ESIM switch will close.

You are correct that it doesn't take too much vacuum to close it. .3-.5 in H2O is all it takes.

I enjoy your vids. When are you going to have some pretty models to do the demos? I think I speak for the group when I say I'd appreciate you enhancing your videos like that.

Joe

**greasybob** · 04-30-2011, 08:56 PM

Thanks, here's the first video I tried to make of the NVLD with the vehicle running (sorry, no show girls). This was before I realized you could open and close the NVLD with a hand held vacuum pump. 1 PSI equals 27 inches water column, you have to get used to those numbers, 27 seems like a lot other wise. It would be nice to see the NVLD data when using the purge vapors test. http://www.youtube.com/watch?v=FPF9XYuCZRI

**funrazor23** · 04-30-2011, 10:57 PM

Im not sure but I have in the past grounded out the middle of the 3 wire connector on the nvld with the vehicle running this should close the valve and allow for a smoke test. I am pretty sure I found this on identifix or Iatn but it works perfectly

**greasybob** · 05-01-2011, 05:25 AM

The NVLD is not controlled like most other solenoids, it is permanently grounded and must be energized to be activated. Should also add that energizing or activating the solenoid will vent the fuel tank, not seal it.

**Joe Rappa** · 05-01-2011, 08:10 AM

Originally posted by funrazor23

Im not sure but I have in the past grounded out the middle of the 3 wire connector on the nvld with the vehicle running this should close the valve and allow for a smoke test. I am pretty sure I found this on identifix or Iatn but it works perfectly

Hi funrzr,

The NVLD systems are a bit different from the LDP systems. The older LDP systems checked the EVAP system by pumping in a small amount of air and seeing if it holds pressure. The newer NVLD and ESIM use vacuum generated as the fuel tank cools off. The NVLD solenoid is only turned on when the EVAP system is being purged, so no vacuum develops in the tank during purge. You can't seal the EVAP system by energizing the NVLD solenoid. It has to be plugged mechanically if you want to leak check it.

Joe

**Crusty** · 05-01-2011, 08:55 AM

Originally posted by greasybob

OK, Joe, I think I figured out a way to check the NVLD functionality with a hand held vacuum pump, my Verus and my Super smoker. I tried a few other techniques as well but because the necessary scan data pids were missing and you can't do function tests with the engine running, this worked best. Not the greatest video but I think you'll get the idea. I'll post the failed attempts later. http://www.youtube.com/watch?v=a3KIl3gNNAs

No Way Bob.....Say it isn't so......

"the necessary scan data pids were missing "

Incomplete and innacurate information from the equipment.... AGAIN

SHSHSHSHSHSSHSH we're not supposed to notice

MISSING PIDS

**Crusty** · 05-01-2011, 09:00 AM

Originally posted by Joe Rappa

Nice job Bob. You tested the same way I do. It's quick and effective. You can also just hold the car at high idle and watch for the purge valve to open. As soon as it hits around 25% or so (if I remember correctly) the NVLD or ESIM switch will close.

You are correct that it doesn't take too much vacuum to close it. .3-.5 in H2O is all it takes.

I enjoy your vids. When are you going to have some pretty models to do the demos? I think I speak for the group when I say I'd appreciate you enhancing your videos like that.

Joe

HMMMMM

"in H2O "

interesting observation.

**greasybob** · 05-01-2011, 01:48 PM

I had an old NVLD from an 05 Dodge Neon, so I opened it up and here is the autopsy report with my attempt to explain it's functions. If there are any mistakes or I left anything out please feel free to add to it. http://www.youtube.com/watch?v=0QCLqXx6SGI It seems to me that if pressure were to start to build in the tank that the larger diaphram that closes the micro switch when there is vacuum, would push down on the solenoid valve on the bottom which would then release the pressure. Even though the pressure would be the same on both the diaphram and the valve, the larger area of diaphram would still over come the pressure on the valve.

Oooh the pressure!

Oooh the pressure!

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