Blazer gas tank plugged vent tube at the tank. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Mike C · 03-07-2021, 12:20 PM

We completely rebuilt a '72 Jimmy for my son. Original tank. It was flushed out and looks good inside. Now that the truck is on the road we have found the vent tube going into the tank is plugged. I can put 100psi of air pressure on it and it just blows back out the vent opening. If you hold the rubber nozzle on it tight enough after you stop adding air and let off, it vents pressure back out. So NOTHING goes into the tank.

Anybody had one of these tanks cut apart? Is there some sort of one way valve inside the tank? Trying to push a coat hanger through it forcibly contacts something, and that does not happen in the smaller charcoal cannister fittings. I have an air vacuum pump I may try to hook and and see if it might pop a valve loose.

**Steeveedee** · 03-07-2021, 12:28 PM

There is only a valve at the vapor canister that opens when vacuum hits it- when the truck is running. There should be nothing blocking the flow of fuel vapors to the canister. It probably has some crud in the line. The line runs up the back of the cab on the passenger's side before going to the canister.

**Sheepdip** · 03-07-2021, 04:11 PM

Put a vented cap on it and forget about it.

**BigBird05** · 03-07-2021, 04:59 PM

Could be you are a victim of a mud dauber wasp.

Mike C · 03-07-2021, 07:29 PM

I completely flushed the tank when we took the truck apart. The two 5/16 lines for the charcoal cannister are clear. The 1/2" vent to the filler is not... I could not push a coat hanger through it. I put a vacuum on it and nothing. I sealed up everything else on the tank and put 90 psi of air on one of the 5/16 lines. It caused the tank to expand and then pushed fuel out the filler neck. I soaked it in Seafoam before this.

It is completely and perfectly 100 % blocked. In the mean time I have routed the filler neck vent to one of the 5/16 nipples. My brand new fuel sender failed after the first full tank of fuel so the tank has to come out again. I will investigate more at that point. If I cannot get that one to vent I will tee the two 5/16 into the 1/2 vent line.

Mike C · 03-07-2021, 07:31 PM

Quote:

Originally Posted by Sheepdip

Put a vented cap on it and forget about it.

You can't fill it up with the filler neck vent blocked. After about a gallon of gas, it burps the next 1/2 gallon down the side of the truck.

**DeadheadNM** · 03-07-2021, 11:54 PM

Does the fuel filler neck match this one piece style? The vent at that end of the tank should just be an open tube no valve.

Mike C · 03-08-2021, 10:04 PM

It looks just like that. But there is something in the tank vent. It is COMPLETELY blocked inside the tank. Cannot force a coat hanger in it and pressurizing it with my air compressor doesn't put any air into the tank.

**Steeveedee** · 03-08-2021, 10:45 PM

SheepDip has your solution.

**Sheepdip** · 03-09-2021, 12:44 AM

Quote:

Originally Posted by Mike C

You can't fill it up with the filler neck vent blocked. After about a gallon of gas, it burps the next 1/2 gallon down the side of the truck.

Maybe your gas station nozzles in TX are different than Kalifornia's but we have the vapor recovery type that vents your tank as it fills.

My avatar has no tank vent except the vented cap and I can fill it as fast as the pump will pump.

03-07-2021, 12:20 PM	#1
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,709	Blazer gas tank plugged vent tube at the tank. We completely rebuilt a '72 Jimmy for my son. Original tank. It was flushed out and looks good inside. Now that the truck is on the road we have found the vent tube going into the tank is plugged. I can put 100psi of air pressure on it and it just blows back out the vent opening. If you hold the rubber nozzle on it tight enough after you stop adding air and let off, it vents pressure back out. So NOTHING goes into the tank. Anybody had one of these tanks cut apart? Is there some sort of one way valve inside the tank? Trying to push a coat hanger through it forcibly contacts something, and that does not happen in the smaller charcoal cannister fittings. I have an air vacuum pump I may try to hook and and see if it might pop a valve loose. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

03-07-2021, 12:28 PM	#2
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,083	Re: Blazer gas tank plugged vent tube at the tank. There is only a valve at the vapor canister that opens when vacuum hits it- when the truck is running. There should be nothing blocking the flow of fuel vapors to the canister. It probably has some crud in the line. The line runs up the back of the cab on the passenger's side before going to the canister. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

03-07-2021, 04:11 PM	#3
Sheepdip Senior Member Join Date: Nov 2018 Location: Waterford California Posts: 2,365	Re: Blazer gas tank plugged vent tube at the tank. Put a vented cap on it and forget about it.

03-07-2021, 04:59 PM	#4
BigBird05 Senior Member Join Date: Aug 2019 Location: Cheraw Posts: 1,305	Re: Blazer gas tank plugged vent tube at the tank. Could be you are a victim of a mud dauber wasp.

03-07-2021, 07:29 PM	#5
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,709	Re: Blazer gas tank plugged vent tube at the tank. I completely flushed the tank when we took the truck apart. The two 5/16 lines for the charcoal cannister are clear. The 1/2" vent to the filler is not... I could not push a coat hanger through it. I put a vacuum on it and nothing. I sealed up everything else on the tank and put 90 psi of air on one of the 5/16 lines. It caused the tank to expand and then pushed fuel out the filler neck. I soaked it in Seafoam before this. It is completely and perfectly 100 % blocked. In the mean time I have routed the filler neck vent to one of the 5/16 nipples. My brand new fuel sender failed after the first full tank of fuel so the tank has to come out again. I will investigate more at that point. If I cannot get that one to vent I will tee the two 5/16 into the 1/2 vent line. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

03-07-2021, 11:54 PM	#7
DeadheadNM Carpe manana Join Date: Dec 2010 Location: Eau Claire, WI Posts: 12,280	Re: Blazer gas tank plugged vent tube at the tank. Does the fuel filler neck match this one piece style? The vent at that end of the tank should just be an open tube no valve. Attached Images __________________ 1972 K5 CST Highlander Blazer: http://67-72chevytrucks.com/vboard/s...d.php?t=708547 1972 K20 Cheyenne Super: http://67-72chevytrucks.com/vboard/s...d.php?t=528308 Members met: ORANGBLAZ, 2003 silverado, MikeCofield, BB72CHEVKT, Duncan&Son, Sameyrasmea72, THENEWMEXICAN, HotRod C/10, brianthelion02, Sport/Truck, ryanroo, michael bustamante, Dirt's72, Already Gone, WestButteTruck, 57taskforce, Moreyel, painterljp, AASmedic, SoCoC10, Lumaestas, carbuff382, Chevyland

03-08-2021, 10:04 PM	#8
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,709	Re: Blazer gas tank plugged vent tube at the tank. It looks just like that. But there is something in the tank vent. It is COMPLETELY blocked inside the tank. Cannot force a coat hanger in it and pressurizing it with my air compressor doesn't put any air into the tank. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

03-08-2021, 10:45 PM	#9
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,083	Re: Blazer gas tank plugged vent tube at the tank. SheepDip has your solution. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA



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