Charcoal canister question (7.4)

[Brian71583]

I'm jumping the gun here as I don't even have the truck at my house right now if I were there but I figured I'd ask this question while its on my mind. Recent purchase of a '96 C3500 Crew Cab Dually. It has a few issues I'm working through but the main was is getting the transmission rebuilt so troubleshooting of some issues such as this one have been more mental than physical since driving wasn't possible.

The charcoal canister on this guy makes a pretty audible suction sound constantly. Not right at startup but soon after and once it starts it is constant. It comes from the center port that only appears to have a guard over it. Not sure if its an intake or a vent but its certainly moving an audible amount of air.

I've never heard this before in any of my vehicles from that era. Any ideas? I'm sure the whole EVAP system on this truck is messed up. It appears to have the wrong filler neck on the truck and the filler vent hose is patched in at least 2 places.

 

[someotherguy]

Cannister purge solenoid might be stuck open, just a guess though.

Richard

 

[xXxPARAGONxXx]

Also, a lot of charcoal canisters have filters. You may want to check externally to see if there is a filter that can be detached, inspected, and cleaned or replaced if necessary.

(Might not apply to yours.)

 

[GM Guy]

Im working through a recent purchase of mine, a 97 454,and i thought it had a weak pump, nope,pump is fine, however, I think the purge solenoid was stuck open and it sucked the tank in and bent the pump assembly enough that the pressure hose off the electric pump popped off the feed tube.

So make sure and get the evap issues figured out sooner than later. lol

I sat the new pump in gently, and it wouldnt come close to fitting, so I put my hand down inside and found the kinked up floor...so loosened the clamp, slid hose onto the pump, tightened, then stuffed that bent mess back into the tank and at least it runs now. lol
New pump will wait in the box till I get a new tank.

 

[454cid]

Cannister purge solenoid might be stuck open, just a guess though.

Richard

Are you talking about the solenoid that's on the intake, or the one that's on the side of the canister? My truck puts a vacuum on the tank, too.

 

[GM Guy]

Yes, the solenoid on the side of the intake