Plugged fuel tank vent line.....effects???

[turbonut85]

if the 5/16" vent line from the tank to the charcoal canister is plugged solid...what driveability issues would this cause??

 

[earlbrown]

If the gas cap it tight, most likely you'll run rich if the tank is warm. After drawing fuel down, you'll lose pressure. If it drops enough to starve under boost I guess the first symptom would be lean popping.

How in the world did you notice it was clogged?

 

[Chuck Leeper]

Pull enough fuel out to cause a vacuum, and it will cause the pump to cavitate, ruining it.

 

[BEATAV8]

install a vented gas cap it'll be fine.

 

[Chuck Leeper]

A vented gas cap w/ the fill neck pointing to the rear of the car??

 

[turbonut85]

Been chasing low BLM, rich idle, and KNR during spool up....(comes on around 12-15 psi, then drops off right away as the 2nd pump comes on...also been having issues adjusting fuel pressure...so I blew out the return line, and that's when I checked the vapor line...plugged solid...can't even blow through it with a 180psi air compressor...

 

[Silver Fox]

A friends car had this. We just ran a new high pressure rubber fuel line to fix it. Rob

 

[BEATAV8]

A vented gas cap w/ the fill neck pointing to the rear of the car??

You bet.

 

[BEATAV8]

Been chasing low BLM, rich idle, and KNR during spool up....(comes on around 12-15 psi, then drops off right away as the 2nd pump comes on...also been having issues adjusting fuel pressure...so I blew out the return line, and that's when I checked the vapor line...plugged solid...can't even blow through it with a 180psi air compressor...

more than likely it's plugged at the fuel header. the stock vent is orificed and that's a really small hole. its located inside the vent tube where the tube passes through the header.

 

[turbonut85]

Define fuel header...??

 

[gnfanatic]

sheesh, my vent line in the engine bay has a fuel filter on the end of it for like 10 years now.

 

[BEATAV8]

Define fuel header...??

also called the fuel pump hanger

 

[turbonut85]

Has a Reds double pumper...with a new stainless hanger made by Red Armstrong. I disconnected the hose before the fuel tank....line is plugged somewhere between the engine compartment, and the rear crossmember....which is strange since I replaced all of the steel lines in 2008 when I did the frame-off restoration...

Back to the original question....(I know how to fix the plugged line) what other issues would a plugged vent line cause, and why??

 

[BEATAV8]

Depends upon how the fuel pressure regulator reacts. The regulator is referenced to intake manifold pressure, but if the tank pressure changes substantially...... could that be seen in the fuel rail?

I run my tank non-vented. It has only a vented cap (air allowed in, no vapors out). The tank does pressurize when it warms up, but it does not appear to affect the fuel rail significantly. I have a fuel pressure transducer on the fuel rail plugged into my powerlogger and have come to expect 38psi at idle just about all the time.

To find out if yours is getting messed up somehow you would need to monitor the rail pressure.