05 Chevy Z71 OBD II Fuel Tank Vent - Truck Forums

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Old 08-02-2010, 12:55 AM
Thread Starter
Join Date: Jul 2010
Location: South of Wichita, KS
Posts: 11
Default 05 Chevy Z71 OBD II Fuel Tank Vent

Hi Group,

I need some help from people smarter than me.

I recently bought a Chevy Silverado Z71 Off Road extended cab with a 5.3 L Vortec. I got a really good deal on it so I am fixing it up. I've had it for 3 weeks now and have had both good luck and bad so far.

So this is my next problem. There was a recall on the fuel tank vent solenoid at the charcoal canister. It seems they have a tendency to get plugged with dirt being mounted just in front of the rear axle. I had an OBD II code for the solenoid and found out it was a dealer only item. So I asked the Chevy dealer and was told it would cost $250 plus parts. The guy told me how to fix it myself so I bought the new solenoid kit, and 15 ft. of heater hose and did it myself. I had to relocate the breather filter forward of the fuel tank. My problem is, he didn't tell me how far forward to go with it? I ran it all the way up to the engine compartment. Did I just build a fire hazard under my hood? Or does the breather only breath in? I don't want to run it until I know it's right.

I don't know if this is part of the same problem or not but now I can't get the tank to fill past half way without shutting off the automatic nozzle on the fuel pump. I can trickle it in but it just isn't right.
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Old 08-03-2010, 03:09 AM
Join Date: May 2010
Posts: 54

not sure about the hose problem... but are you sure that your sending unit is not bad? are you sure you dont already have half a tank of gas??? just a suggestion and not saying that you dont know what you are doing, just giving a suggestion.
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Old 08-03-2010, 07:14 PM
Thread Starter
Join Date: Jul 2010
Location: South of Wichita, KS
Posts: 11

Thanks for the suggestion 02camarossle. You are right in thinking I should trouble shoot in the right sequence. I just got lazy and did a redneck shortcut. I went to the pump and attempted to fill the tank. The pump shut off when the gage read 1/2 a tank. Out of curiosity I trickled gas in until the gage read full. It took about 5 minutes and I think about 13 gallons of gas to completely fill. Since then I have read blogs from all over the US from people experiencing the same problem with their 05 Silverados. I just haven't found a viable answer to the problem yet. Most people suggest that the inner-tank vent line leading back up to the top of the fill neck may be plugged but I have checked that. I think it has to do with the fact that these trucks have no actual fuel return from the engine to the tank. They just vent the tank itself with the charcoal canister and vent solenoid close to the tank. I'm just a shade tree mechanic, am I understanding the system right? I'm reading a Hanes manual from Autozone. No answers there either.
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Old 08-03-2010, 11:34 PM
Join Date: May 2010
Posts: 54

im not exactly sure how that charcoal canaster works, all i know is it's for emissions... i have never had a problem with mine on my 02 so i can not help you trouble shoot any more than that... all the advice i can give you is make sure that the sending unit is not bad... to be honest with your pulling the gas tank is not all that hard, you and a buddy could do it in about an hour taking your time, just make sure you disconnect the fuel lines and fuel pump harness. good luck finding your problem.
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Old 08-04-2010, 12:33 AM
Join Date: Jul 2010
Posts: 22

The system consists of an EVAP Purge Solenoid, a Charcoal Canister, a Pressure Vacuum Filler Cap, and a Rollover and Pressure Relief Valve.

The evaporative emission system prevents gasoline vapors in the fuel system from escaping into the atmosphere. When the vehicle is not running, fuel in the fuel tank evaporates. The vapors travel through vent hoses or tubes to be stored in the charcoal canister. Once the vehicle is running, these vapors are drawn into the engine and consumed with combustion gases.

Visual Inspection:
  • Check routing and condition of all vacuum hoses. SEE Vehicle Emission Control Information (VECI) label, (underhood).
  • Ensure all vacuum hoses and electrical wires are routed a minimum of three inches from the exhaust manifold, to prevent deterioration due to high temperatures.
NOTE: Use only fuel resistant hoses when servicing the evaporative control system.
Purge Shutoff Switch Test:
  1. Check vacuum hoses for proper routing.
  2. Remove fuel vapor hose from canister and plug.
  3. Remove purge hose from intake manifold.
  4. Remove vacuum signal hose from purge switch and install vacuum pump.
  5. Blow on purge hose, passage should be closed. (If passage is open replace Purge Switch/Canister assembly).
  6. Apply vacuum (15 in/Hg) to signal port of purge switch.
  7. Blow on purge hose, passage should be clear. (If passage is closed replace Canister-Purge Switch assembly).
  8. If Purge Switch is operating properly, reinstall vacuum and vapor hoses.
NOTE: The Charcoal Canister and Purge Shutoff Switch are usually a combined unit and are not serviced separately. If the purge switch or cannister is defective the complete assembly must be replaced.
NOTE: A faulty Purge Shutoff Switch can result in increased emissions and/or poor driveability.
Rollover and Pressure Relief Valve Test:
  1. Inspect fuel and vapor hoses for proper routing, cracks, or restrictions.
  2. Inspect fuel tank cap for proper seal and fit.
  3. Remove fuel tank vent hose from EVAP Canister. Apply light air pressure (3-6 psi.) to the Fuel tank filler tube. Air flow should be present at fuel tank vent hose. If air flow is not present, and Fuel Tank is not over-full, replace Pressure/Relief Rollover Valve.
NOTE: In vehicle rollover valve is in the inverted position the plunger is forced against the guide plate and raw fuel is prevented from flowing through the valve orifice into the fuel tank vent tube.
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Old 08-06-2010, 12:34 AM
Thread Starter
Join Date: Jul 2010
Location: South of Wichita, KS
Posts: 11

truckboy, That's an awesome diagram. How did you do that? There is another fitting missing in the diagram though. it is the breather box that mounts to the canister. It's a small box about 2"x3" filled with plastic expanded foam for a filter. I take it to be the vaccuum relief for the canister. This filter was plugged with Oklahama red dirt causing an OBD code. The recall fix is to disconect the filter from the canister and relocate it foward so it will be somewhat out of the dirt. I replaced the gas cap, Evap purge solenoid, and put a fuel resistant hose between the canister and the filter to move it foward out of the dirt. Since I moved the breather filter all the way to the engine compartment, I am worried that gas fumes will cause a fire hazard under the hood. Any thoughts?
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Old 12-22-2011, 11:48 PM
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Join Date: Dec 2011
Location: Indiana
Posts: 2
Default fuel milege problems on my 97 chevy truck

I recently bought a 1997 Chevy 1500 with the 350 engine with throttle body. It uses alot of gas. i thought it was leaking somewhere but i checked it out and its is not. The truck runs really smooth at itle. even at like 700 RPM. and it never cuts out while driving. When i bought the truck i had to replace the fuel pump. when i got the pump out and took out the sending unit i seen someone drilled a hole in the top of the sending unit to run a ground wire straight to the fuel pump. I know my truck has a evac system so i filled the hole around the wire with silicone to seal it. My father has a 200 chevy truck and he gets really good gas mileage. What do you think is wrong where do you think my fuel is going. I dont even notice the pressure from the tank when i loosen the fuel cap. Does the evac system improve fuel economy? Like i said it runs good at idle and while driving just uses alot of fuel. even on the highway with the cruz on. I drove 17 miles and back and it used a 1/4 tank of fuel. Its really starting to irritate me. I just dont understand these new fuel systems. with the vacuum and evac systems. please someone give me some information that will help me out. Thanks!
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Old 12-23-2011, 06:16 AM
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Join Date: Jun 2008
Location: New Hampshire
Posts: 227

When installing the relocate kit I mount the end of the hose at top of trans by trans vent line.
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Old 01-27-2012, 11:29 AM
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Join Date: Jun 2009
Posts: 87

I had the same prob with my 05. Vent was plugged and setting off codes so i got the update kit and put the vent up by the tranny like acnas. But then the code came back and i still had trouble putting gas in it, kicked off when it wanted. Took for ever to filler up.

Did a bunch of messing around to find that my Evap Canister was plugged.
It has been 4 months and the code hasn't come back and i can fill up my truck without it kicking off.

Best way i think to test the Canister without a scanner and procedures...Try blowing threw it. My new one took no effort, my old one was like blowing a grape threw a straw.

Just make sure its the canister, cause there kinda pricey and some auto stores wont let you send them back. Mine was 260 plus tax and i could not send it back. luckly it was my prob

Hope this helps
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