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Trouble pumping gas....


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If the EVAP canister filter attached to the side of the gas tank is clogged it will not allow air in/out of the tank, thus not allowing fuel in. This problem usually comes in conjunction with a TIGHTEN FUEL CAP message being displayed via the information center readout because of an EVAP system leak.


OR if it only happens once in a blue moon the fuel filter in the station gas pump is blocked and there is nothing wrong with your truck.6bff667b72a931ba8c36f6eb0b0a83af.jpg


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I looked up that EVAP canister for my truck but shows that part don't apply? Think it's 02 and before that have those. Not real sure... does the 04 model have them?

Edited by BoostedBlues (see edit history)
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Its the solenoid that goes bad. Its the round thing near #4 in psualumni's picture. It sucks in fine dust, and eventually sticks the solenoid shut, making for the slow gas fill. You can take it off and clean it, or replace it, but that is a short term fix. GM's fix was to replace it, and run the intake up under the hood with a long piece of heater hose. Looks a little hoaky, but it works. You shouldn't need to remove the box or gas tank to do any of it.

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The solenoid goes bad, but the canister does, too. Especially if you're in the habit of topping off the tank after the pump clicks off automatically.


I've replaced my solenoid with the new design that has the remote-mount filter, hoping that's all it would need, nope. Also have new OEM gas cap. Still have the "tighten gas cap" error message, and still have trouble filling up the truck. That symptom is fairly recent; if it had done that consistently I would have just gone ahead and done the canister, which is the next job.



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When I supercharged my truck the supercharger came with a new EVAP purge solenoid (the sensor that sits on the intake manifold and purges the gas vapor from the charcoal canister into the intake). I would assume this is because the new one was supposed to have a stronger check valve inside. (I know from experience, as I have smoked this part on my Cobalt SS running high turbo boost. The increased pressure in the intake at boost popped the check valve inside on the stock unit.) Since I replaced this and my truck is a 2004 (even with only 30k) I decided to replace all the easily serviceable EVAP components. I bought a new gas cap and the purge solenoid that sits on the side of the tank (item 4). Replacing these items can be done without dropping the tank or removing the bed. I was surprised how much faster my tank fills at the pump. Even though I didn't notice a problem before, when I tightened up the EVAP system with new components it allowed air out of the tank faster when I was filling up with fuel, and most likely eliminated small tolerable vapor leaks from the tank.




The irony in all this is that Whipple does not have a provision on their intake and/or supercharger for the PCV system. The fuel system discharge solenoid that used to vent the fuel vapor from the charcoal canister to the intake manifold now vents to the PCV valve on the driver’s side valve cover and vise versa. The line from the PCV valve from factory that also vented to the intake is now connected to the fuel system discharge solenoid. Therefore you have flow from the PCV system to the fuel system discharge solenoid, and from the fuel system discharge solenoid to the PCV valve. This creates a situation where two positive directions of flow are pushing against each other. i.e. The PCV is flowing out to the fuel system discharge solenoid, and the fuel system discharge solenoid is flowing out to the PCV valve. Obviously this creates a situation where the flow goes nowhere deadheading in the hose until it leaks past the PCV valve back into the valve cover.




In this situation the pressure from PCV system finds another route to escape to atmosphere through the engine (better to atmosphere than into my intake anyway I feel. Just don't tell the EPA.) When the fuel vapor from the charcoal canister vents through the fuel system discharge solenoid in to valve cover it mixes with engine oil. This thins it out just a tad im sure, or simply evaporates and exits with the PCV gases to atmosphere. (Again, better than fouling my intake manifold with gunk I think, just don't tell the EPA.) It's a little comical as my EVAP system tells me when the fuel system discharge solenoid vents into the valve cover, because the PCM detects this as an EVAP leak. I'll be driving along and eventually the pressure in the charcoal canister needs to vent via the fuel system discharge solenoid into the valve cover. The PCM detects this pressure deviation in the EVAP system and displays the TIGHTEN FUEL CAP message in the information center. The fuel system discharge solenoid ends the purge, the system reseals, and the TIGHTEN FUEL CAP message goes away. If my wife is with me she hears the chime from the information center and says “What is your truck doing now?” I tell her it’s so powerful it’s reminding me to drive safely. She rolls her eyes. Never complains when the squeezebox pushes her back into the seat through. (Just don’t tell the EPA.) :laugh:

Edited by psualumni (see edit history)
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