Fuel tank not venting, even with vent hose disconnected. Need help!

[thezentree]

A couple weeks ago on a trail ride I broke the studs that fasten the tail pipe to the muffler at some point. This meant that for probably most of the day my exhaust was pointing directly at the cargo area floor (couldn’t hear it because it was after the muffler). It melted my toolbox to the carpet, cooked my elocker harness, and apparently has screwed something up with the way the fuel tank vents, because now it won’t take fuel without me just barely trickling it into the tank. Like, it takes 15 minutes to add 10 gallons. I also got a P0440 code this morning, but it hasn’t come back since I cleared the code.

The exhaust got things hot enough to melt the plastic cladding off of the purge and vent lines above the rear axle.

Putting air to the purge port on the charcoal canister does not result in air exiting the EVAP hose as the FSM says should happen, but the charcoal canister passes all the other pressure checks. I don’t have a vacuum pump to run those tests.

I don’t want to just start throwing parts at this thing but I’m leaning towards it maybe being a bad canister? It doesn’t look like it got hot. I’m not quite sure what else to do to better isolate the issue.

Any ideas? This is the stupidest way to have broken stuff...

 

[vermontmike]

isn't the fuel filler tube a rubber hose from the filler neck to the tank?

 

[LittleCaesar]

If you have access to a smoke machine, I would undo the lines and see if one may have collapsed internally. On most GMs I have worked on, either the canister is clogged or the vent solenoid is dead.

 

[brillo_76]

A couple weeks ago on a trail ride I broke the studs that fasten the tail pipe to the muffler at some point. This meant that for probably most of the day my exhaust was pointing directly at the cargo area floor (couldn’t hear it because it was after the muffler). It melted my toolbox to the carpet, cooked my elocker harness, and apparently has screwed something up with the way the fuel tank vents, because now it won’t take fuel without me just barely trickling it into the tank. Like, it takes 15 minutes to add 10 gallons. I also got a P0440 code this morning, but it hasn’t come back since I cleared the code.



The exhaust got things hot enough to melt the plastic cladding off of the purge and vent lines above the rear axle.



Putting air to the purge port on the charcoal canister does not result in air exiting the EVAP hose as the FSM says should happen, but the charcoal canister passes all the other pressure checks. I don’t have a vacuum pump to run those tests.



I don’t want to just start throwing parts at this thing but I’m leaning towards it maybe being a bad canister? It doesn’t look like it got hot. I’m not quite sure what else to do to better isolate the issue.



Any ideas? This is the stupidest way to have broken stuff...

Dang.. what a bummer. So if it got your elocker harness, it got the canister really good.

So your going to need at least a canister plus probably all the rubber lines from it to the tank.

I doubt it got the tank check valves were affected. As your rig wouldn't run.

My 2001 evap canister was toast and filler were toast due to rust rot.

I just bought a used ones from rust free yard to replace mine. Was my cheapest way out. Instead of buying a pile of little parts.




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[thezentree]

Thanks for all the responses y’all. I haven’t had time to mess with it since I initially posted, but when I get home in a couple weeks I’m going to drop the fuel tank and start checking hoses. My OEM tank skid is pretty banged up and I’m starting to wonder if the venting issue is more related to me knocking debris loose than the exhaust melting things.

While I’ve got the tank down, anything I ought to replace? Thinking sending unit and pump.

 

[19963.4lsr5]

Thanks for all the responses y’all. I haven’t had time to mess with it since I initially posted, but when I get home in a couple weeks I’m going to drop the fuel tank and start checking hoses. My OEM tank skid is pretty banged up and I’m starting to wonder if the venting issue is more related to me knocking debris loose than the exhaust melting things.

While I’ve got the tank down, anything I ought to replace? Thinking sending unit and pump.

If your keeping your tank, at the minimum replace the two gaskets and clean up any rust on the gasket surfaces.


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[thezentree]

This is probably related.

 

[Devbot]

This is probably related.

Image didn't post

 

[thezentree]

Nevermind, too fkn hard to post pictures on this website.

 

[octanejunkie]

Nevermind, too fkn hard to post pictures on this website.

Post on. iFS

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[octanejunkie]

Nevermind, too fkn hard to post pictures on this website.

Cross posted pics for [MENTION=158195]thezentree[/MENTION]

I went four wheeling a few weeks ago on some fairly mild trails a couple hours from here. Nothing too crazy, couple of ledges, some hill climbs, and some water crossings. This was the sketchiest thing I did the whole day.

I drove a couple hours home and noticed my elocker light was on, but the locker wasn’t actually engaged. Tf. So I crawled under the truck and found this.

I opened the back door and pulled all my shit out of the cargo area and found this:

Damn it. The heat from the exhaust melted my toolbox to the carpet. It smells naaaasty.

So I ordered a new exhaust, some bullshit from rockauto, installed it, and figured I’d start messing with the elocker wiring when I got a chance. Couple days later I went to fill up and had to fill slooooowly because the tank wasn’t venting. Also got a P0440 code once. Damn it. So I started poking around that ****ing rats nest of hoses over the rear axle and couldn’t find any issues. I checked the charcoal canister and it passed all the pressure checks in the FSM.

I thought maybe the vent line just coincidentally got plugged around the same time, so I decided to drop the tank and start poking around. Obviously I had just topped off my tank, so I drove around in awd for a few days just to burn as much fuel off as I could. About half the time the traction control started cutting power when I accelerated from a stop, so that’s weird. Guessing I’ve also cooked an ABS wire.

Tank dropped.

First of all, **** the design engineer that crammed all those hoses together. What a nightmare to get 20 year old hoses off of barbs so close together and packed behind a crossmember over the 5 linked axle. You *******.

Second, I think I found my issue:

I guess the exhaust heated up the tubular crossmember enough to melt the evap vent hose where it was laying on top of the crossmember.

Gonna swap sending units and pump filters while I have the tank on the ground.

Anyway, that stupid little trail ride broke:
Exhaust
Elocker harness
Carpet
Toolbox
Vent hose (and by extension all the fuel tank shit I’m gonna replace just because it’s easy to get to now)
ABS sensor?
UCA Johnny joint the exhaust baked

And that’s the dumbest way I’ve ever broken a vehicle.



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[thezentree]

Cross posted pics for [MENTION=158195]thezentree[/MENTION]

I went four wheeling a few weeks ago on some fairly mild trails a couple hours from here. Nothing too crazy, couple of ledges, some hill climbs, and some water crossings. This was the sketchiest thing I did the whole day.

I drove a couple hours home and noticed my elocker light was on, but the locker wasn’t actually engaged. Tf. So I crawled under the truck and found this.

I opened the back door and pulled all my shit out of the cargo area and found this:

Damn it. The heat from the exhaust melted my toolbox to the carpet. It smells naaaasty.

So I ordered a new exhaust, some bullshit from rockauto, installed it, and figured I’d start messing with the elocker wiring when I got a chance. Couple days later I went to fill up and had to fill slooooowly because the tank wasn’t venting. Also got a P0440 code once. Damn it. So I started poking around that ****ing rats nest of hoses over the rear axle and couldn’t find any issues. I checked the charcoal canister and it passed all the pressure checks in the FSM.

I thought maybe the vent line just coincidentally got plugged around the same time, so I decided to drop the tank and start poking around. Obviously I had just topped off my tank, so I drove around in awd for a few days just to burn as much fuel off as I could. About half the time the traction control started cutting power when I accelerated from a stop, so that’s weird. Guessing I’ve also cooked an ABS wire.

Tank dropped.

First of all, **** the design engineer that crammed all those hoses together. What a nightmare to get 20 year old hoses off of barbs so close together and packed behind a crossmember over the 5 linked axle. You *******.

Second, I think I found my issue:

I guess the exhaust heated up the tubular crossmember enough to melt the evap vent hose where it was laying on top of the crossmember.

Gonna swap sending units and pump filters while I have the tank on the ground.

Anyway, that stupid little trail ride broke:
Exhaust
Elocker harness
Carpet
Toolbox
Vent hose (and by extension all the fuel tank shit I’m gonna replace just because it’s easy to get to now)
ABS sensor?
UCA Johnny joint the exhaust baked

And that’s the dumbest way I’ve ever broken a vehicle.



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Dawg! Thanks for that.

 

[Bad Luck]

That’s impressive but not in a good way

 

[thezentree]

Yeah and I think that list is going to include a charcoal canister now too. I got the tank back in yesterday and went to fill up and it did the same shit. I'm gonna pull the evap hose off the canister and try filling up again just to confirm its the canister (idk what else it would be at this point), but jfc this is getting expensive.

 

[jgue467]

Mine did the same thing for about a couple months a few years back.

I think I may have overfilled it once or twice (going too many clicks past first stop).

So I just tried filling at stations that are not level, placing my fill side up higher, didn't solve it entirely yet it helped fill faster.

Then I just let it sit and dry out for a couple weeks and it just started filling again as normal, got lucky this time.

 

[thezentree]

Yeah and I think that list is going to include a charcoal canister now too. I got the tank back in yesterday and went to fill up and it did the same shit. I'm gonna pull the evap hose off the canister and try filling up again just to confirm its the canister (idk what else it would be at this point), but jfc this is getting expensive.

Maybe not?

I pulled the brand new evap hose off the charcoal canister, so it’s basically 3 feet of open 1” tube to the fuel tank (rollover valve is brand new too) and it still won’t take more than 1/10 of a gallon without clicking off. Tank was almost full (scangauge said I had burned 2.5 gallons since I topped it off the other day), so could the rollover valve float be closing that vent? I would think not since that’s how the tank vents during fill up, right?

I’m out of ideas and about ready to take it to a shop and let someone else deal with it.

 

[thezentree]

Maybe not?

I pulled the brand new evap hose off the charcoal canister, so it’s basically 3 feet of open 1” tube to the fuel tank (rollover valve is brand new too) and it still won’t take more than 1/10 of a gallon without clicking off. Tank was almost full (scangauge said I had burned 2.5 gallons since I topped it off the other day), so could the rollover valve float be closing that vent? I would think not since that’s how the tank vents during fill up, right?

I’m out of ideas and about ready to take it to a shop and let someone else deal with it.

what
the
f*ck

Fuel tank vents but also doesn’t. Wtaf. - YouTube

 

[thezentree]

Bump for the video link in the previous post.

Need some emissions/EVAP experts.

The vent hose that connects the rollover valve on the top of the tank to the charcoal canister is the primary vent for fuel filling, right?

If that's the case, disconnecting that vent hose from the charcoal canister should effectively leave the fuel tank open to atmosphere, right?

There's a little diaphragm valve in the top of the rollover valve assy that's "driven" by a vent line that goes to the top of the fuel filler neck, but I think it just equalizes pressure in the tank and passively closes the tank off if the tank pressure drops below atmospheric pressure.

For the life of me I can't figure out why the tank won't vent with that vent hose open to atmosphere when I'm adding fuel, but it's clearly open when I add a little compressed air.

Any thoughts? I ordered a borescope that should be here tomorrow so I can check the filler neck for any obstructions but that seems like a long shot to me.

 

[Bad Luck]

Bump for the video link in the previous post.

Need some emissions/EVAP experts.

The vent hose that connects the rollover valve on the top of the tank to the charcoal canister is the primary vent for fuel filling, right?

If that's the case, disconnecting that vent hose from the charcoal canister should effectively leave the fuel tank open to atmosphere, right?

There's a little diaphragm valve in the top of the rollover valve assy that's "driven" by a vent line that goes to the top of the fuel filler neck, but I think it just equalizes pressure in the tank and passively closes the tank off if the tank pressure drops below atmospheric pressure.

For the life of me I can't figure out why the tank won't vent with that vent hose open to atmosphere when I'm adding fuel, but it's clearly open when I add a little compressed air.

Any thoughts? I ordered a borescope that should be here tomorrow so I can check the filler neck for any obstructions but that seems like a long shot to me.

The vent hose is for venting excess fuel vapor/pressure during normal operation for the evap system. The small lines by the filler neck are what vents air while you fill the tank. Trace and check that. I don’t remember if it’s one or two small hoses/lines at the filler neck.

 

[thezentree]

The vent hose is for venting excess fuel vapor/pressure during normal operation for the evap system. The small lines by the filler neck are what vents air while you fill the tank. Trace and check that. I don’t remember if it’s one or two small hoses/lines at the filler neck.

There are two of them in the filler neck I think. I'll take another look at them tomorrow afternoon but I did check them and they passed air pretty easily. Edit: or at least they seemed to.