UPDATED* Carbon in Purge Valve = just do extra PM?

[nick0789]

2005 Z71 Tahoe, 186k miles all stock

Long story short, I got the “tighten fuel cap” message on my cluster again and decided to just change the purge valve and vent valve. When I pulled the purge valve fitting, carbon pellets fell out and I saw the solenoid was packed full of pellets as well (which is likely where my message came from); pelted fell out of the EVAP line when I shook it as well.

I know I’ll need to replace the canister at this point, but I went ahead and got most of the lines for the EVAP system as well (I still need to order the line from the purge valve at the intake back to wherever the connection is). My question, that I figure I know the answer to, is twofold:

1) I’m assuming I’ll need to drop the tank to access the EVAP lines on the top of the fuel tank, correct? I’m on vacation and don’t have good pics to evaluate before I go ahead and order parts for 2) below.

2) I figure the fuel pump to be original, so if I have to drop the tank I might as well say screw it and eat the cost in order to save future labor time and just replace the fuel pump as well for preventative maintenance, right? If so, what brand is preferred (if not GM)?

 

[OR VietVet]

I recently did all this on my 05 Z71. Do the entire evap system or deal with additional problems and drop the tank for a new fuel pump. If you have gas system instead of flex fuel, I can give you all the part numbers you need. 8th digit of the VIN is "T" or "Z". T is the gas engine.
Mine is all documented, with pics, at my build thread and I did it all without a problem ahead of time. I knew it would need it all eventually, so I did it all.

 

[Fless]

Need to know if your truck is Flex Fuel or not, as indicated by @MO VietVet.

I'm not familiar with the non-Flex Fuel evap routing around the tank, but the Flex Fuel evap lines by the tank can be removed from the side by pulling them out of the plastic retainers. You'll probably need to either slightly lower the tank, or remove the metal shield on the passenger side of the tank.

Here's what a 2004 Flex Fuel tank looks like from the top. I've dropped the tank both ways: with and without removing the evap lines (they're "on" in the pic below, on the righthand side of the tank). Non-Flex will look different, but I'm not sure how.

 

[nick0789]

I have the gas system. These are the part numbers that I currently have:

GM 88983154 (vapor lines)
GM 15104151 (canister vent line)
GM 215-464 (canister)

For the line to the intake, is it GM 15275274? I wanted to confirm before ordering.

I have the new purge valve on stand-by, and the canister vent is already installed.

What PN did you use for the pump?


If I have the potential to not drop the tank (I have smaller arms) to replace the lines that would be ideal. I can’t find the build thread at the moment, as I am on my phone and searching the forum isn’t the easiest for me.

 

[OR VietVet]

Pump: MU1639

Valve/Solenoid: 214-1105

Valve/Solenoid: 214-2149

Cannister: 215-464

Cannister bracket: 15113366

Cannister valve hose: 12575527

Cannister valve hose: 88983154

Line to intake: 15275274

 

[OR VietVet]

 

[nick0789]

Pump: MU1639

Cannister valve hose: 12575527

Line to intake: 15275274

I got these parts ordered, and will have something “fun” to work on over the thanksgiving holiday. Thanks for the part numbers!

About how long did it take you to do the replacement? Aside from getting out as much fuel as possible and the compression clips, are there any other surprises that I should expect? I didn’t see anything out of the ordinary after watching a few videos on YT

 

[OR VietVet]

You pretty much covered it. The videos cover it all but watch more than one video. Start to finish was 5 hours but I had a friend that owns a shop and we used his lift. Just be careful and patient. Check in the tank for any crap in there.

 

[nick0789]

Got everything replaced last night and it turned over just fine, though I have a vacuum leak somewhere since I hear a faint whistle/whine while accelerating.

My biggest problem is that I can’t fill the tank, now. I get 3-4 seconds and then the pump shuts off. I checked everything with the filler neck at least 6 times while reinstalling so I don’t know what’s going on. Any ideas?

Edit: I pulled the large line from the canister and attempted to fill. Still got shut off (new gas station) after about a gallon. I did notice a little fuel dripping from the line that was removed … would it be possible to just have some fuel in that line that is blocking the venting process? I did drop the two vent lines from the pump into the tank so I wouldn’t be surprised if that’s the case? If it is what are my options?

 

[nick0789]

Just for added information, I lowered the tank again last night and none of the EVAP lines appeared to be kinked or otherwise obstructed. My only guess at this point is fuel in the lines that connect to the in-tank portion of the fuel pump.

If I pull the EVAP lines off the fuel pump, can I blow air into the ports and back flush fuel out of the lines or am I missing something else that would be easier to test?

I did also pull the rubber line from the filler neck to the tank and was able to poke the metal flapper inside the neck of the tank and it moved freely, so my lack of venting must be causing this issue.

 

[nick0789]

Well, I don’t know what changed over the course of a few days but I went back to the first gas station, same pump and was able to fill to full with no shutoffs.
My only guess is the vent line just needed to be purged by driving or expansion of the tank contents. Either way, no more issues with filling.

I do keep getting some charcoal at the purge valve and I’m just thinking it’s from the middle EVAP line that I wasn’t able to replace. Speaking of which, is there a writeup somewhere to replace that middle EVAP line (connecting the line on the tank to the line at the intake)? It’s pretty long but I can’t trace it behind the engine so I’m not sure where it actually runs.

 

[iamdub]

Well, I don’t know what changed over the course of a few days but I went back to the first gas station, same pump and was able to fill to full with no shutoffs.
My only guess is the vent line just needed to be purged by driving or expansion of the tank contents. Either way, no more issues with filling.

I do keep getting some charcoal at the purge valve and I’m just thinking it’s from the middle EVAP line that I wasn’t able to replace. Speaking of which, is there a writeup somewhere to replace that middle EVAP line (connecting the line on the tank to the line at the intake)? It’s pretty long but I can’t trace it behind the engine so I’m not sure where it actually runs.

It's just a pipe- blow it out.

WARNING: Use very light puffs of pressure. If you have a small air compressor with a 1/4" hose and small blow gun- you're golden. I went all power monger on mine and hit it with 150+ psi from my shop compressor. It actually wedged the carbon pellets in the bends of the piping from trying to shoot them out so hard and fast. I had to beat and bend the curved parts to crack the impacted pellets loose so the air would move them out. I disconnected the flex line where it met the tank and at the purge valve on the intake manifold and blew it, back and forth, from both ends until nothing more was coming out and I didn't hear anything rattling through the lines when blown. After I was sure it was empty, I hit it with full air power and it was very strong on the other end, indicating the line was all clear.

 

[Timdenn180]

It's just a pipe- blow it out.

WARNING: Use very light puffs of pressure. If you have a small air compressor with a 1/4" hose and small blow gun- you're golden. I went all power monger on mine and hit it with 150+ psi from my shop compressor. It actually wedged the carbon pellets in the bends of the piping from trying to shoot them out so hard and fast. I had to beat and bend the curved parts to crack the impacted pellets loose so the air would move them out. I disconnected the flex line where it met the tank and at the purge valve on the intake manifold and blew it, back and forth, from both ends until nothing more was coming out and I didn't hear anything rattling through the lines when blown. After I was sure it was empty, I hit it with full air power and it was very strong on the other end, indicating the line was all clear.

I thought the line from the purge solenoid goes to the canister? Wouldn’t you disconnect from purge solenoid under hood and then where it comes off canister

 

[iamdub]

I thought the line from the purge solenoid goes to the canister? Wouldn’t you disconnect from purge solenoid under hood and then where it comes off canister

Ultimately, it does go to the canister. But the line runs from the purge solenoid on the side of the intake manifold, along the frame, then to a pre-formed hose that's mounted to the tank with a quick-disconnect near the frame. It doesn't go into the tank, just uses it for mounting and routing. I already had my tank removed and all the lines off of it to clean them out. So, the remaining line was that one on the frame with the short flexible portion that would've connected to that short run secured to the tank.

 

[nonickatall]

Check if your vent valve opens when you turn off the ignition. This is responsible for allowing the air to escape when you fill your tank with petrol if it happens again.