How to keep evap system from failing?

[88lance]

Hello everyone, got a new '02 Tahoe here. I live down a dirt road, and my '05 Tahoe and 2011 Sierra already can't take fuel because of a screwed up evap system.
From what I read, dust gets in some part of the system and ruins it and it will just constantly do this and you have to keep replacing it.

I had a few questions, especially since I just picked up this '02.

-what part is actually failing? Is it the canister, or the solenoid?
People say to replace the solenoid, but it seems like that wouldn't affect fuel going in, that sounds like the canister. Maybe somebody could explain what's going on there.
So on the '05 Tahoe we cleaned out the canister, tank, and lines and put it back on, and it fuels great but the engine light is still on saying something about the EVAP system. So that plan didn't work. Lol

- how do I prevent this from happening on the '02? What's getting dirty that's causing it to fail? Do I need to protect the solenoid or the canister somehow to prevent this?

 

[strutaeng]

It's the vent solenoid that is supposed to get sand and salts and sticks (pretty sure it's more of a rust belt region vehicles.) I've never had any issues with the EVAP on my 99 Silverado NBS. I thought there was more EVAP issues on the 03-06 models, not sure why.

Watch a YouTube video from Wells for an explanation of how the GM EVAP system works. It's actually pretty simple.

It's this channel. They've got another video that's more about fundamentals and theory of operating, but I couldn't find it

 

[88lance]

It's the vent solenoid that is supposed to get sand and salts and sticks (pretty sure it's more of a rust belt region vehicles.) I've never had any issues with the EVAP on my 99 Silverado NBS. I thought there was more EVAP issues on the 03-06 models, not sure why.

Watch a YouTube video from Wells for an explanation of how the GM EVAP system works. It's actually pretty simple.

Great, from what I've seen online the solenoid seems pretty quick and simple to replace.
That will probably fix the engine light on the '05.
I'll check out the video about the system.
Is there a way to protect this from future failure in the dust?

 

[Fless]

The GMT900s have a kit that relocates the evap vent solenoid, so you might look into doing something like that. Always add fuel with the ignition off; this ensures that the vent valve is not commanded closed. Never fill past the first click of the pump; adding more fuel can saturate the canister.

It would be interesting to know what code is persisting on the '05. Evap issues are common, but the system is relatively simple. Could be a purge valve malfunction, fuel pressure sensor malfunction, etc.

https://static.nhtsa.gov/odi/tsbs/2021/MC-10198890-9999.pdf

Remember that there are very specific conditions to be met for the system to run the evap test. Must be done on a cold start, and mine will run it within about 3 miles or less:

Conditions for Meeting a Cold Start
• The ignition voltage between 11-18 volts.
• The barometric pressure (BARO) is more than 75 kPa.
• The start-up engine coolant temperature (ECT) is between 4-30°C (39-86°F).
• The start-up intake air temperature (IAT) is between 4-30°C (39-86°F).
• The difference between the IAT and the ECT is less than or equal to 6°C (10.8°F)
• The ambient air temperature is between 4-30°C (39-86°F).
• Fuel level is between 15-85 percent
• Without RPO LMG--The fuel alcohol content is less than 15 percent.
• With RPO LMG--The fuel alcohol content is less than 87 percent.

 

[strutaeng]

Great, from what I've seen online the solenoid seems pretty quick and simple to replace.
That will probably fix the engine light on the '05.
I'll check out the video about the system.
Is there a way to protect this from future failure in the dust?

I was going to say maybe run a hose from the vent valve to a filter or loop it higher somewhere?

But sounds like there's already a kit?

@Fless do you know if the vent valves are the same for both body styles?

 

[Fless]

I was going to say maybe run a hose from the vent valve to a filter or loop it higher somewhere?

But sounds like there's already a kit?

@Fless do you know if the vent valves are the same for both body styles?

I don't. Haven't researched it.

EDIT: the filter is integrated with the valve in the GMT800s, while it appears to be more remote in the GMT900 version. There may be a way to use the newer one with the NBS systems.

 

[88lance]

So the filter is a different thing than the canister? Because mine has two separate things I think, the big box canister, and then the circular solenoid thing.
The '05 is at my sister's house right now, I'll run by and get the code out of it tomorrow.
If the solenoid getting dirty is what's causing it to start fueling slow, the relocation kit for that would be great.
So the canister with the charcoal failing is a whole separate issue from dust getting in the system and it fueling slowly?

 

[Fless]

The filter is in the vent valve housing in the '05, above the rear diff. The canister is in front of the fuel tank. Either one could cause slow fuel filling. I don't know if the later NNBS version of the vent valve could be retrofitted to the NBS connections.

You can test the vent valve by disconnecting it from the electrical and the evap hose. Alternately apply 12v DC to the terminals -- polarity doesn't matter -- while blowing into the hose connection. With no voltage applied (like when the ignition is off) you should be able to blow air through it. With voltage applied, it should be plugged. Do this several times; mine was intermittent and didn't always close, which told the system there was a leak.

 

[strutaeng]

Yup, I also did the testing of the vent valve by connecting it to the battery on my 06 Suburban.

I was trying solve a small EVAP leak. I tested the vent, purge (bench tested ok with a handheld vacuum pump and also 12VDC) and I think the voltage of the tank with a DVOM at the ECU connectors. I didn't have a scanner that showed this at the time. Everything checked ok

I bought a $600 smoke machine and couldn't find any obvious leaks. That truck has the dual tank setup, so I thought maybe a tiny leak in one of the hoses somewhere I could detect? IDK...so I gave up and resorted to HP Tooners. :-(

 

[88lance]

Well I got pretty busy and haven't been back to this thread in a while.
But I was messing with my mini shop vac the other day and took the top off to clean the filter, and noticed it has a little dust bag filter with an elastic band on top.
So this gave me an idea.
I went and bought a replacement filter bag (they are about the size of a Ziploc sandwich bag).
I took the solenoid off, and cut a hole for the plug to go through.
I slid the filter bag over the solenoid, with the elastic band opening wrapped around the vent hose. I clipped it back up there, and plugged the wire back in through the hole in the bag.
I ziptied the excess closed around the hose, and put it back in the mount.

Since dust is what's causing this to fail, I'm curious if this will at least delay the failure of it since I live down a dirt road.

My concerns are what it might do if it gets wet, and then I drive down the road. It might seal off with mud and not let any air through, but on the other hand I'm not sure if that would really matter or not as long as it's clean inside.

Time will tell I guess