2001 Suburban 8.1 Flooding

[Brasky]

Hello new member here. I have a 2001 Suburban 2500 LT with the 8.1 and the weird dual fuel tank system.

When I fill the gas tank until the pump clicks off, it will flood the motor out at idle. If I hold the gas pedal down it will keep running. I do not overfill the tank.

If I shut the pump off a couple of gallons before full there is no issue.

I have replaced the purge solenoid on the intake manifold, the canister vent by the rear axle, and cleaned out the vent that is up near the fill tube. When the vehicle floods out, I notice the canister vent by the rear axle will have fuel in it if I unhook it.

Removing the gas cap does not make a difference.

Any suggestions? I haven’t replaced the charcoal canister yet as this doesn’t seem to be caused by a failing charcoal canister.

 

[Fless]

Here's a possibility: if your canister has fuel in it (it shouldn't) then when the PCM tells the purge valve to open, fuel, instead of vapor, may be sucked into the intake. One clue you have that the canister has fuel in it is that the vent valve gets wet. That vent should be fumes only, and opens to equalize the fuel system pressure when commanded or the engine is off.

I'd say it's probably time to unhook the canister and see if it drips fuel out of the connector, and see if you can push air through it fairly easily.

 

[Brasky]

Here's a possibility: if your canister has fuel in it (it shouldn't) then when the PCM tells the purge valve to open, fuel, instead of vapor, may be sucked into the intake. One clue you have that the canister has fuel in it is that the vent valve gets wet. That vent should be fumes only, and opens to equalize the fuel system pressure when commanded or the engine is off.

I'd say it's probably time to unhook the canister and see if it drips fuel out of the connector, and see if you can push air through it fairly easily.

Would a charcoal canister full of fuel only cause issues when the gas tank is full?

Just as a side note I’ve had this suburban about five years and it’s happened since purchase (70,000 miles ago). I’ve tried to fix this issue before with no luck

 

[Fless]

Just noodling this, maybe the canister isn't quite full, and filling the tank tops it off. Then that excess is immediately burned by the engine through the purge valve. Really just a SWAG; stranger things have been known to happen.

Typically a full canister would prevent or inhibit filling the tank, since if the fumes can't get through the canister and out the vent valve, the tank is essentially being pressurized by pumping gas. Nowhere to vent.

 

[Sam Harris]

Just noodling this, maybe the canister isn't quite full, and filling the tank tops it off. Then that excess is immediately burned by the engine through the purge valve. Really just a SWAG; stranger things have been known to happen.

Typically a full canister would prevent or inhibit filling the tank, since if the fumes can't get through the canister and out the vent valve, the tank is essentially being pressurized by pumping gas. Nowhere to vent.

Agree, and with a dual tank setup, it’s a different ballgame. The fact the canister has fuel in it, is definitely a problem. We just have to figure out why.

 

[Brasky]

I’m hoping to take the charcoal canister out tonight or tomorrow and I’ll report back. Thank you for the help so far

 

[Brasky]

Charcoal canister appears fine and doesn’t have resistance when I blow air into it. No fuel in it. I’m glad because it’s located on top of the cross member between the gas tank and transfer case and there is no way to fit it between either to remove. Appears you’d have to lower the gas tank to get it out

There was some liquid gas in the hose that comes from the tank to the vent canister solenoid (the one by the rear axle). This is with the tank only 3/4 full. I’m no expert but it seems to me the problem is somehow liquid gas is entering the tube between the tank and the vent canister solenoid when I fill the tank full.

Anyone have any other ideas?

 

[Brasky]

Well I fixed it. The hose going to the canister seemed excessively long and was dropping down way below the canister. When I filled it with gas the hose would fill with gas causing this issue. I relocated the hose as high up against the body as I could and no more problem

 

[Sam Harris]

Well I fixed it. The hose going to the canister seemed excessively long and was dropping down way below the canister. When I filled it with gas the hose would fill with gas causing this issue. I relocated the hose as high up against the body as I could and no more problem

Thanks for the follow up! Glad it’s been fixed.