Posted on 08/03/2017 1:19:24 PM PDT by rickmichaels
It’s a habit many of us as drivers have and exercise every day – when refueling, we keep clicking at the nozzle handle to round out our purchase or to squeeze every last kilometer possible out of tank-full. But did you know that feeding your vehicle enough fuel, especially until it levels out well into the filler neck, can cause problems with emissions systems?
Every vehicle on the road that meets current emission controls’ regulations has some type of vapour control system. It’s there to capture raw fuel vapors from escaping into the atmosphere. With most gasoline powered vehicles, this system usually involves a canister with a charcoal medium, sensors, valves, and lines.
When fuel is removed from a station’s underground storage tank and pumped into the tank of a vehicle, the change in the temperatures it’s exposed to can cause the fuel to create non-liquid vapours. The same thing can happen when the fuel in the vehicle is exposed to the normal sloshing from driving.
With some systems, any errant fuel vapours are simply controlled and piped forward to the engine’s intake to be burned in a normal combustion cycle. With others, these emissions are directed back into the tank. An air-tight canister does the job of temporary storage of these vapours.
So what happens when the tank is chock full of fuel? This can create enough positive pressure in the tank to cause the vapour control system to have problems due to the lack of expansion space in the tank. It can lead to failed valves and seals and, in rare cases, it may actually bulge the tank, rendering it in need of replacement. As a vehicle ages, the likelihood of these failures increase as our sometimes dry and salt-laden road environment takes its own toll on small-diameter hoses and plastic components.
If your vehicle does develop a problem with this system, its onboard computer will illuminate the check engine light. The trouble code that will be stored will often be called a ‘small evaporative leak,’ which means a cumbersome diagnostic process to determine the exact location of the leak. Techs will often have to hook up a specialized piece of shop equipment to such a vehicle, which introduces a non-toxic yet visible ‘smoke’ vapour into the system that will help pinpoint the leak’s source.
As you might suspect, this can lead to an hour or more of diagnostic time and its related fees, not to mention the cost of any replacement components and installation charges. Think invoices well over $200 or more. This one trouble code is consistently one of the 10 biggest causes of a check engine light.
Avoiding this trouble and its related expenses is as easy as shutting off the fuel station nozzle action at the first click when the tank is full. As most of us pay at the pumps with some sort of plastic, trying to round out the purchase is rather meaningless. And any money saved by trying to jam as much fuel as possible in when a particular station is offering a low price is often less than a few pennies and more than offset by any repair bills that might come up down the road.
It's possible that crud has partially blocked this pipe, so that you're no longer fully filling both tanks.
Here is a forum link explaining another guy's problem:
http://www.ft86club.com/forums/showthread.php?t=74249
And here is his hand-drawn schematic of the fuel tanks:
From the beginning, my old man taught me to always refill at 1/4 tank or at very least look for a gas station at 1/4 tank. I only ignored this advice once in my driving lifetime and I very nearly ran out of gas in the middle of rush hour traffic. I was literally sputtering on fumes and my car engine shut off as I was coasting up to the refill station. Never again.
Automobiles since 2005 have a sensor and if you top your tank off you risk wrecking it. I think it was called an EOV ?
[ Two words:
Subaru Forester
What a LEMON! That and the engine gasket problem. ]
Reminds me of this:
FIAT - Emission Free since Delivery from the dealer.
FIAT - The only gas it burns is the tow truck driver’s
[ From the beginning, my old man taught me to always refill at 1/4 tank or at very least look for a gas station at 1/4 tank. I only ignored this advice once in my driving lifetime and I very nearly ran out of gas in the middle of rush hour traffic. I was literally sputtering on fumes and my car engine shut off as I was coasting up to the refill station. Never again. ]
If your car or truck has a electric gas pump in the tank you never want to go below 1/8th of a tank because running the pump dry will cause extra wear an tear to the pump and it also uses the gas in the tank to lubricate and cool the pump parts.
My brother explained this to me when he replaced the fuel pump in my car.
I usually run ethanol free on the daily driver.
The old stuff gets it exclusively.
In years gone by, my wife drove Subaru wagons. They were O.K. In recent times, I laugh at their PZEV logo on the rear of the vehicle. Partial Zero Emission Vehicle? They apparently do have SOME emissions. Sounds like “leak resistant” boots....as opposed to leakPROOF boots. The salesman said the boots will leak, but they don’t want to.
I think that I would need to drive hundreds of miles to do that. Central TX.
I had a 1990 Plymouth Grand Voyager. Just before it reached 200,000 miles the fuel pump gave out so I emptied and dropped the fuel tank. I completely wiped out the interior of the tank and there was no sediment whatsoever.
“so I throw in a $20 when it gets low.”
Man, I wouldn’t do that. Besides throwing away money and taking a chance of running out of gas, you’re running a real risk of clogging your fuel filter.
Also, some bottom-of-tank fuel pumps can overheat when uncovered.
Back in the day a trucker told me that sediment can be a problem if you never let the gar get below 1/4 tank, as some people do. In any of my own fuel tanks which regularly go to “E” I’ve seen no crud.
I used to have a 1962 Fiat 600 D that would do that. It clogged the main jet which I had take out and blow out.
my 71’ international has no emmissions to foul...what B>S>
I don’t know where they’re getting this $200 repair. Cost me $800 on my 2004 Hyundai Sonata. And I was not overfilling because when I bought the car they told me about it.
Essentially this evaporative control system is an expensive pile of junk.
FIAT = Fix It Again, Tony
Sounds like Intellectual Greenie BS.
I have filled my wife’s Lexus 300 to the brim for 14 years and never had a problem.
I have done the same with my 7 year old Ridgeline and never had a problem.
I did the same with my O J Simpson 1996 white Bronco for a decade, and one of our sons has done it for ten more years with that Bronco. No problems.
The intellectual yet Idiot Greenies don’t want us to fill our tanks as it might cause an ice berg to melt in the south pole if we spill a few drops off gas on the pavement in the gas station.
Funny how this never caused a problem until the enviro-nuts decided that topping off your vehicld was “Bad for the environment”
I have been doing it for years, never caused me a problem in the cars I have owned. I always top off.
Almost all gas stations, except maybe the real old mom & pop stations, have a dual filtration system that is very effective.
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