RE: [Chrysler300] 'Negative' gas tank pressure

["Rich Barber" <c300@xxxxxxx>]

Late response as I try to clean up old e-mail.  My 1955 C-300 has a tube
from the tank that is connected so as to vent into the filler neck near its
top.  The filler cap is vented to the atmosphere with a small hole in the
inner gasket.  I think the idea was to allow air and fumes in the tank to
vent through the tube while filling the tank.  The vent tube is connected to
the filler neck so that any gasoline that pukes back up the vent tube will
flow back into the tank instead of down the side of the fender.  The vented
cap allows air to come in and displace fuel used during engine operation and
also allows fumes to escape from the tank as the gasoline vaporizes.  The
twin carbs are also vented to the atmosphere, allowing fuel in the bowls to
boil away and be gone.  As previously reported, I have installed an electric
fuel pump back by the tank to help prime the carbs and make for quick
starts.  

Later technology includes a non-vented tank and filler cap which allows the
tank fumes to flow into an activated charcoal filter and be trapped there if
the engine is not operating or be pulled into the engine when operating.
This is a fairly effective method of keeping the air cleaner and allowing we
operators to capture nearly all of the gasoline we buy.  I'm not sure how
air is allowed back into the tank during use, but I assume there is a
solenoid or check valve somewhere in the system.

CA smog test includes a pressure test of the cap and of the tank itself.
The tank is pressurized and the entire fuel plumbing system is checked for
pressure bleed down and leaks.  Emissions testing is generally done with the
engine under load on a drive-wheel dyno and costs $60 every couple years.
All raw data is transmitted online back to a great computer in Big Brother's
office.  Pre-1975 cars don't have to be smogged--another benefit of driving
vintage iron.  Efforts are afoot, however, to send all the wonderful old
iron off to the scrapper.

Rich Barber
The other Brentwood, CA White Chryslers, no Broncos

-----Original Message-----
From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On
Behalf Of Michael Moore
Sent: Tuesday, August 28, 2012 7:54 AM
To: Lindsey Fuller
Cc: Ron Waters; Chrysler300@xxxxxxxxxxxxxxx; cpaviper@xxxxxxxxxxx
Subject: Re: [Chrysler300] 'Negative' gas tank pressure

My 62 300H has a vent line from the tank to the outside-do the earlier cars
not have such a vent?
Mike Moore

On Aug 28, 2012, at 7:21 AM, Lindsey Fuller wrote:

I believe your conclusion is correct Ron. He should get it vented quickly. I
actually had a replacement tank on my E collapse in all 4 corners from this
negative pressure after redoing the whole fuel system. Would not have
believed this possible unless I had seen it happen. 1/8" hole preferred
solution over installing a new tank,

Lindsey in Winnipeg.

----- Original Message -----
From: Ron Waters <ronbo97@xxxxxxxxxxx>
Date: Monday, August 27, 2012 10:28 pm
Subject: Re: [Chrysler300] 'Negative' gas tank pressure
To: Chrysler300@xxxxxxxxxxxxxxx, cpaviper@xxxxxxxxxxx

> He needs a VENTED gas cap. Or just drill an 1/8" hole in the top of 
> his present one.
> 
> Ron
> ----- Original Message -----
> From: <cpaviper@xxxxxxxxxxx>
> To: <Chrysler300@xxxxxxxxxxxxxxx>
> Sent: Monday, August 27, 2012 11:18 PM
> Subject: [Chrysler300] 'Negative' gas tank pressure
> 
> 
> 
> 
> Was at a local cruise-in this evening, and visiting with fellow 300F 
> owner, Frank Troost. Frank mentioned a problem he had last Sunday with 
> his '57 Adventurer coupe. He said the engine seemed starving for fuel, 
> the glass bowl fuel filter wasn't filling with gas, and when he un 
> screwed the gas cap, there was a huge 'whoosh' of air into the tank, 
> and fuel flowed to the engine. His fuel pump now seems inoperable.
> 
> 
> 
> Does this sound like a gas tank venting issue? I read the archived 
> emails on 'positive' gas tank pressure, but this is the opposite 
> problem.
> 
> 
> Thanks,
> 
> Noel Hastalis
> 
> Burr Ridge, IL
> 
> 300F
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
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Lindsey Fuller
300 E,F

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