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The garage told me I had to replace the vent valve in the…

The garage told me...

The garage told me I had to replace the vent valve in the gas tank it will run right for 20 minutes then it turns to crap it's like it's running out of gas weird is that vacuum line run

Mechanic's Assistant: When did you last fill the tank? And do you smell gasoline around the engine?

It's been awhile since I filled it up and no I don't smell no gas at the front or the back

Mechanic's Assistant: What is the model/year of your Chevy?

1999 blazzer 4wd. 4 door. 4,

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

They had it in the garage for 3 days they have tried mass air flow sensor new distributor cap rotary button wires plugs even check the charcoal filter box it seems to be okay someone told them to check the vent on the opposite end of the tank they messed with it it will run now but not for a long period before it cuts out

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

I just want to know if the vent valve in the gas tank can cause these problems

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Answered in 2 minutes by:
3/28/2018
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Yes. As you burn gas, the tank has to draw fresh air in, or else it will draw a vacuum on the tank and fuel flow will stop. I assume the vent valve is stuck closed, that must be what they determined. I am surprised they didn't just replace it, since they replaced the MAF, distributor cap and rotor, spark plugs, etc. A new vent valve is about $35 and takes ten minutes to replace.

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Customer reply replied 3 months ago
Do I have to drop the tank to replace that and where does the vacuum hose lead off of the vent valve

The vent valve is near the canister behind the tank. It has one large hose attached to it, which goes to the canister. The system is normally open, this vent valve only closes once in a great while, so the computer can test the EVAP system for leaks. If it's stuck closed, you're going to have problems like you're describing.

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Customer reply replied 3 months ago
Okay thank you let you know how it goes

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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
Verified
Jerry Newton and 87 other Chevy Specialists are ready to help you
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Customer reply replied 3 months ago
The one I bought shows it goes on the opposite end of the tank just a little round one with a vacuum hose on it
Customer reply replied 3 months ago
The vent valve that I have goes on opposite end of the tank about big is a 50 cent piece or so with one vacuum hose
Customer reply replied 3 months ago
it duz. So what's the little one on the other end of the tank with a vacuum hose on it that's the one they worked on
Customer reply replied 3 months ago
If the EGR but is valve will that give me the same problem I had before
If you have a stuck open egr valve you will have a rough idle but it will otherwise run just fine.
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Customer reply replied 3 months ago
Can the vent vent valve on the gas tank make it run for a minute and die
No not likely
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Customer reply replied 3 months ago
If you can give me some idea what to look for sometimes it will run fine for 15-20 minutes sometimes it don't run fine at all I am lost

I would put a fuel pressure gauge on the engine, attach the gauge to the windshield so I could see it, then drive it until it starts acting up. At that point, I would want to see what the fuel pressure is doing.

Same for exhaust back pressure, remove oxygen sensor and install back pressure gauge, drive it until it acts up, then see what the back pressure is doing. Catalytic converters and fuel pumps are the two heavy hitters on S10 Blazers.

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